The guide of Marine Frequency Converters. marine EQUIPMENT

Transcription

1 The guide of arine Frequency Converters marine EQUIPENT

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3 Table of contents 1 INTRODUCTION 4 2 TECHNICAL DESCRIPTION FOR ARINE FREQUENCY CONVERTERS 5 Siemens arine frequency converters 5 AC motors controlled by arine frequency converters 5 Overview of the arine frequency converter operation 6 The arine frequency converter's load on the power supply 7 3 APPLICATIONS WITH ARINE FREQUENCY CONVERTERS 7 arine frequency converter used in diesel-electric propulsion 7 Booster 9 Cargo pumps 9 Winches 11 Thrusters 12 Fans and cooling systems 13 Other applications 14 4 OTHER ISSUES 15 Energy saving 15 Pump characteristic with throttle valve control 15 Pump characteristic with speed control 15 Electromagnetic compatibility (EC) 16 Harmonic currents and tuned filter circuits 17 Harmonic distortion of mains supply 17 arine frequency with three possibilities for Bus communication 18 Communication with PROFIBUS 18 Communication between drives by Siemens DRIVE-CLiQ 18 Commissioning and service with a Personal computer 19 Dynamic load limitation (DLL) 19 SUARY 20 3

4 Introduction The shipping industry is facing ever greater challenges, especially regarding energy saving and the environment. Lurking in the background are political shadows like CO 2 duties and dire predictions concerning the cost of fuel in ten years time. Authorities and owners are consequently focusing more and more on shipping concepts involving less environmental risk and energy saving. Shipping installations having higher fuel efficiency in all operational stages will be increasingly favored and will presumably have great potential for future growth. Additionally, the requirements of reliability, redundancy, maneuverability and concerning long maintenance intervals and short service response time are gradually becoming stricter. Parts of these requirements can easily be met by controlling the speed of electric motors. In this guide, you will get a brief introduction to the operational principle of a frequency converter, its construction and application. When connected to a frequency converter, an AC motor exhibits unique properties in providing rotational speeds from standstill to values in excess of the rated speed, and also in maintaining exact torque control. The arine frequency converter system represents a new concept due to its uniform power range. The regulation and control properties of arine frequency converters enable the use of the same type of frequency converters with all drives on board. Even hydraulically operated equipment may advantageously be replaced by arine frequency converters and electric motors. This brochure will guide you through the majority of applications of arine frequency converters on board a ship, pointing out the advantages of using them. It will present to you the properties of arine frequency converters in given applications and suggest the corresponding solutions. At the same time, we will present the possibility of integrating arine frequency converters in automation systems. Any frequency converter will by nature create distortions in the supply voltage and can thereby cause disturbances to other on-board equipment. We will present how to avoid such disturbances by the selective use of arine frequency converter configurations and show the potential for improvements. 4

5 Technical for arine frequency Description2 converters AC motors controlled by arine frequency converters arine frequency converter Siemens arine frequency converters Frequency converter requirements vary with respect to functions, the required survey and the uniformity of control throughout the power range. The frequency converter should also be connectable to all system supply voltages. The new arine frequency converter family from Siemens has been developed for the ship industry market and complies with all the associated requirements. The arine frequency converters can also be delivered with rectifiers drawing a pure sine-shaped current, thereby reducing total harmonic distortion to less than 1%. All frequency converters in the arine design have the following properties: Frequency conversion using IGBT technology Uniform control philosophy Same type of control panel Identical electronic solutions and basic functions Identical connection of control functions Identical commissioning technique Open software for customized applications A function (a parametric number) given in one unit has the identical meaning in all other units found in the range. The same applies to the function of the signal terminals and their allocation. The same also applies to functions like diagnostic memory, trace and reaction to faults. All units react in the same way to control commands. This is an important advantage to you as user: if you know how to use one arine converter, you know how to use them all. arine frequency converters from Siemens is the first frequency converter system on the market covering all kind of applications with the same frequency converter philosophy. Here, the smallest units may be used for driving pumps and fans, while the larger units may drive transverse thrusters and motors for main propulsion. You will deal with only one concept with respect to operation and maintenance. Frequency converters using Pulse Width odulation (PW) inverter units provide the most favorable technical and economical solution for controlling AC motors. New IGBT transistor technology components favor AC motor drives. Highly integrated microelectronic components having powerful calculation capabilities and nearly unlimited storage possibilities make it possible to realize large and complex functions at low cost with small space requirements. The speed-controlled AC motor has been a major innovation in all branches of industry, and the rapid rate of innovation will cause a further increase in the need for such drive systems. The quality of a speed-controlled drive depends on the accuracy and the dynamic ability of the power exertion (the torque) to be transferred to the driven machine and also on how precisely the speed regulation can be controlled. Additionally, it is extremely important to achieve optimum efficiency and to minimize power consumption. Today, it is almost unthinkable to drive modern machinery without speed-controlled drives. Economical as well as technical conditions must be evaluated when investing in new motor drive technology. Disregarding the efficiency of the motor and the frequency converter, the load on the primary power source is the active power required by the working machinery at any time only. This will be the case even when the motor operates in the partially loaded area, i.e. with unity power factor against the mains. The onboard generators are not loaded with reactive power and do not need be dimensioned for this. The figure below shows the typical efficiency factor of a motor and a frequency converter throughout the speed range with a constant load torque at all speeds. arine frequency converters use optimum Pulse Width odulation (PW) causing the connected motors to maintain a high efficiency and high torque utilization over the complete speed range. The efficiency curve throughout the speed range for a arine frequency converter controlled motor otor Converter Total Speed n/n rated [%] 5

6 Large drives such as diesel-electric propulsion systems normally get their electrical power from three or more diesel engines. Here is a great potential for energy saving in using only the number of diesel engines needed for the desired propulsion and the other energy needs on board. Auxiliary diesel engines will no longer be needed and the planning of maintenance becomes easier. A diesel-electric propulsion system enables a more flexible and optimal positioning of the heavy and bulky components and will at the same time reduce the total requirement for area and space. Simultaneously, improved system planning will result in reduced service costs. Cooling water pumps and fans also represent a great energy saving potential since they are dimensioned according to classification requirements with respect to temperatures. The result is the use of excessive energy in pumping unnecessary volumes of air and water through the system. For much of the year, air and water temperatures are normally considerably lower than the criteria used as the basis for the classification requirements. Investment in arine frequency converters with integrated temperature regulation will soon pay for itself. For other uses such as winches, thrusters, discharging pumps, etc., a arine frequency converter-fed AC motor will exhibit better operational features than hydraulics. A arine frequency converter will regulate the speed accurately and make the motor yield an exact pre-set torque. The rugged squirrel cage motor may be controlled to give a uniform torque from standstill to well beyond the rated speed. Speed-controlled motor drives have the following advantages: Lower investments Energy saving in the partial load range Low maintenance costs as wear of machinery and materials are saved by the controlled motor operation Less space in relation to hydraulic or diesel solutions Technically better process solutions: Improved operation reliability Less wear, less maintenance Simple monitoring and operation Fast and safe fault diagnosis Economically friendly operation Diesel-electric propulsion of a luxury yacht Overview of the arine frequency converter operation The task of the frequency converter is to convert the fixed frequency and voltage of the power supply (mains supply) to a variable frequency and voltage for feeding the motor. The speed of the motor will change linearly with the frequency. In order to exert an exact control of the motor torque, it is important to keep the ratio of voltage and frequency constant throughout the speed range of the motor, i.e. V/f = constant; is the magnetization flux of the motor. The rectifier of the arine frequency converter converts the AC supply voltage to a constant DC voltage, and the task of the AC inverter is to transform this DC voltage into a variable AC voltage. The arine frequency converter performs this energy conversion in an almost loss-free way. The efficiency of the arine frequency converters lies in the range of %. The power rectifier, consisting of diodes or thyristors, does this in a way to ensure that the current drawn from the supply is in phase with the supply voltage, i.e. the arine frequency converter will only draw active power from the supply, i.e. almost unity power factor, and there is no need for reactive power. Ignoring the efficiency factor of the motor and the arine frequency converter, the motor drive will only draw the active power at any time needed by the driven load. This also applies when the motor operates in the partial load range. The high efficiency of a speed-controlled squirrel cage motor throughout the speed range is superior compared with other forms of drives. V 3AC V 50/60 Hz t Rectifier DC link V Inverter V t 3AC 0 - V rated t The construction of a pulse width modulated arine frequency converter with power rectifier, intermediate circuit and AC converter 6

7 The arine frequency converter's load on the power supply The figure below shows the principle of a arine frequency converter controlled motor drive. The two graphs show the current, voltage and power supplied to the motor or driven machine and corresponding conditions on the supply side as a function of the motor speed. The condition here is that the driven machine requires a constant torque T over the speed range. The physical relation between torque T and power P is T [Nm] = P [W] / n [rpm] We see from this that the output power P will increase linearly with the motor speed n when keeping the torque constant. Because the control system of the arine frequency converter ensures that the motor operates with constant magnetization, the motor current will be directly proportional to the torque T, i.e. I [A]. k. [Nm]. The condition for a constant magnetization is that the applied voltage V increases proportionally to the frequency f, i.e. V/f = constant =. The basic physical law stating that P is the product of voltage V and current I, i.e. P = V. I is evident from the diagrams. 3AC V 50/60 Hz Rectifier DC link Inverter 3AC 0 - V rated Feeder side otor side n rated n [rpm] Power and current load on the mains and motor when operating a constant torque loaded motor through its speed range I P V V P T I Current I Power P Voltage V n rated n [rpm] Voltage V Power P Torque T Current I Noting how the physical factors on the supply side of the converter changes as a function of the rotational speed when keeping the torque of the working machine constant, the absorbed power P i from the power source must necessarily be identical with the output power of the motor P o when ignoring the efficiency. As the power voltage V is constant and the physical condition P = V. I must be met, the current I, which the arine frequency converter draws from the power supply, will increase proportionally to the motor speed, even when the motor current I and the torque remain constant. These two currents will be identical only at the rated motor speed. From the given physical conditions, the current load will be very low at low speeds or at low loads. Starting a motor directly from the power source, the motor current will be 6 7 times the rated current. When using a arine frequency converter, the source current will be only a fraction of the rated motor current. This means that the mains voltage drop caused by a arine frequency converter-controlled motor, small or large, is negligible. Applications with3 arine frequency converters arine frequency converter used in diesel-electric propulsion For most types of vessels, a diesel-electric propulsion system is superior to a conventional diesel system with respect to technical, operational and economical aspects. The five most important aspects making a diesel-electric propulsion system attractive are: Reduced maintenance work Increased reliability Better maneuverability Improved environment Considerable saving in energy A diesel-electric propulsion system is normally equipped with two propellers and three or more generators, giving high availability. One or four propeller systems are also not uncommon depending on the type of vessel (e.g. for large ferries). A system of four diesel engines will normally be the most flexible system. The number of engines simultaneously in use will depend on the desired thrust and the speed of the propellers. This implies that the number of engines in operation will be restricted to the actual number needed for restoring the energy balance. The highest availability will be achieved when three diesel engines are in operation and the vessel can still maintain 90 % of its maximum speed. With a system of this kind, an auxiliary diesel engine is superfluous. This means that planned maintenance may be performed without jeopardizing system reliability. In large propulsion systems where arine frequency converters use a three-winding front transformer, a special front feeding system is used for charging the DC link circuit of the arine frequency converter. When using the Active Front End (AFE) as the feeding system, an input transformer is not applicable in case the line voltage is equal to the input voltage of the drive system. With this system, the harmonic distortion is not only extremely low (less than 1 %) but a power factor compensation of the power line is also possible. achine room with electrical motors each 3 W

8 Advantages of diesel-electric propulsion systems Diesel engine Generator ain switchboard Transformer arine frequency converter Induction motor G G G G A diesel-electric propulsion system with generators and two propulsion propellers In conventional propulsion with variable diesel engine velocity, the specific fuel consumption varies with the speed of the engine (see figure on page 5). This can often be found in smaller ships, in which the velocity of the ship is not controlled by a pitch shift propeller but by the velocity of the engine. There is a point of optimum fuel consumption for one certain speed, which in this form of propulsion is not reached very often, as it relates to only one fixed velocity of the ship. Now using a variable speed drive with diesel-electric propulsion, the speed of the boat is neither regulated by the pitch shift propeller nor by the variation of the diesel engine velocity, but by the arine frequency converter and the electric motor. Therefore, the main power plant of the ship, the diesel engine, can always run at the point of optimum fuel consumption. The effect: Less sooting of the diesel engine, thereby less maintenance. Smaller, high-speed diesel engines that have lower prices. Lower fuel consumption. In total: lower costs. Economically favorable Optimal fuel consumption of the diesel engine for generating electricity Less sooting due to optimum operation with respect to rotational speed and load range High efficiency factor throughout the speed range Reduced maintenance cost due to increased service intervals caused by optimum operation time of the diesel engines Better conditions of maintenance planning inimum downtime for maintenance and service Flexible use of generators Operational reliability odular construction and redundant systems with a minimum of possibilities for total loss of propulsion Radical reduction of moving mechanical parts Experience through more decades with the used electrical components TBF (ean time between failure) is vastly improved using a diesel-electric system with fixed propeller instead of a conventional system with controllable pitch propeller Flexibility The modular construction of a diesel-electric propulsion system permits a flexible placement of onboard units: No long propeller shafts ore practical location of diesel engines Reduced space and area requirements Flexibility in the choice of diesel engine speed Easier to make a sectioned engine room Propulsion room with one 736 kw motor for bow thruster and one 900 kw motor for a retractable azimuth propeller Fuel consumption in relation with speed Power [kw] Torque [Nm] Specific fuel consumption [g/kwh] Speed [rpm] 8

9 arine frequency converters for booster Booster drives increase the main power propulsion of vessels by using an electric motor in combination with the main engine. They support the ship's diesel engine when accelerating, relieve it over the complete speed range, guarantee consistently high speeds and improve its efficiency. In the diagram below, you will find an overview of a booster drive system implemented in an electrical system. Propulsion Booster For on-deck location, the motors must have a degree of IP56 heavy sea protection and must often have an explosion-proof design. Speed-controlled pump drives using arine frequency converters provide much better flexibility, efficiency and noise level than hydraulically-driven pumps. Also pump-related special Technology software can be part of this solution for protection of the pump and a higher productivity of the total pump system. arine frequency converters offer both speed and torque control and with AC motors of high thermal reserve, supreme flexibility can be achieved in a pump system of this kind. The figure shows the high torque obtained with Siemens AC motors used in conjunction with arine frequency converters, even above the rated motor speed. Diesel engine Torque T/T rated [%] Constant flux range Field weakening range Generator G G G G ain switchboard Example of a booster drive system with 3 auxiliary generators Utilization according to temperature class F Utilization according to temperature class B The Booster drive can operate in conditions such as: ain engine is out of order. This means that the propeller of the vessel is controlled over the Booster drive. In case the vessel is at crawl speed, the main engine can be switched off and propulsion power is delivered by the Booster drive. When the main engine is running at nominal power and the speed has to be increased. Highlights for this device are: ain engine and main generator can be smaller due to the fact that additional propulsion power can be supplied by the booster. Also the auxiliary generators will be used more optimally. Lower energy consumption especially in partial loads. Also fuel saving by switching off the main engine at crawl speed. Less maintenance due to the fact that auxiliary engines are running at optimal condition and main engine is not used at low speed where low power is applicable. arine frequency converters for cargo pumps In connection with transport of goods, we need equipment for loading and unloading ships. These are for example pump drives for oil tankers, chemical tankers or edible-oil tankers. As the arine frequency converter system is of a modular construction, it is possible to customize pump concepts according to the number of pumps, their sizes and their simultaneity factor. The pump drives with associated electrical motors are either located in a pump room or longaxled pumps are used with their motors placed on deck Typical torque utilization characteristic for a self-cooled squirrel-cage motor as a function of speed AC-connected systems Input power to the arine frequency converter feeding the cargo pumps comes from a circuit breaker via the main distribution board. Each cargo pump has its own arine frequency converter and is individually controlled. The arine frequency converters communicate with the automation system via conventional I/O signals or via serial communication channels, for instance PROFIBUS, Ethernet, and CAN-Bus. The arine frequency converter may form part of the main switchboard or be mounted in separate cubicles or cabinet systems. Cargo pumps with AC-connected system ain switchboard 3AC 380 / 690 V, 50/60 Hz Frequency [Hz] AC Busbar 9

10 DC-connected system Especially where pumps are not to be simultaneously operated, it may be practical to allow the arine frequency converters to be fed from the main switchboard via two rectifiers or Active Front End. The rectifiers or Active Front End in turn feed each converter via a DC busbar. The dimensioning of the rectifiers should be based on the simultaneity factor of the pumps, and not on the totally installed pumping power. The advantage of such a system is that the total dimensions of the main switchboard including the arine frequency converters are optimized. ain switchboard 3AC 380 / 690 V, 50/60 Hz ain switchboard 3AC 380 / 690 V, 50/60 Hz = = = = = = = = = = Cargo pumps with DC-connected system DC Busbar AC-connected low-voltage drives in cross connection One arine frequency converter is feeding a combination of cargo pumps but is controlled individually. The power of the arine frequency converter depends on the power of the pumps, the amount of pumps which can be in operation and if it is necessary to start a pump on a running converter. It is also possible for example to control two different types of motor power ratings on one arine frequency converter by means of selection in the arine frequency converter. All contactors (output and interconnection) and pumprelated Technology software are controlled by the arine frequency converter itself by using the PLC and process functionality inside the low voltage drive system. Furthermore, a connection to the automation system is possible. For maximum availability of the pump drive system, an emergency control is available in front of the low voltage drive cubicle. With this solution, an unloading of the tanks is still possible in case the overall automation system is out of order. Block diagram of a pump drive system by means of cross connection An interconnection between each low voltage drive system is also available for maximum availability of the pump system. In case a arine frequency converter is out of order, an interconnection can be made to the other one to ensure that the tanks can be unloaded. Thereby you guarantee maximum availability of the pump system. All contactors (output and interconnection) and pumprelated Technology software are controlled by the arine frequency converter itself by using the PLC and process functionality inside the low voltage drive system and a connection to the automation system is also possible. Cabinet of cargo pump 10

11 Operator desk ain switchboard 3AC 380 / 690 V, 50/60 Hz Touch panel Remote access Interface connection I/O or serial communication Block diagram of a pump drive system by means of a matrix connection AC-connected system in matrix connection The output of each low-voltage drive arine frequency converter is connected to a contactor matrix. All low-voltage drive converters are controlled over PROFIBUS by a SIATIC PLC system which controls: The contactors in the matrix by distributed I/O modules. On the touch-screen mounted in front of the converter drive system information on the status of the system as well as an emerging mode can be selected. Interface connection to the overall automation system (for example cargo computer) by I/O signals or of a serial communication link, for instance PROFIBUS, CAN-Bus and Ethernet. Interface connection by I/O or serial communication with operator panel. Interface connection by serial communication with touch panel. Faster diagnosis, shorter downtime, reduced maintenance cost by using remote access. Easy upgrading or adding of supplementary services. The matrix combination provides maximum flexibility and availability. arine frequency converters for winches Windlasses, mooring winches, etc. have until now mostly been equipped with hydraulic or pole changing motor drive systems. Winches using squirrel cage motors and arine frequency converters have improved operational features and a simplified total concept. The robust squirrel cage motor provides a standstill torque twice the rated torque, and at the same time, the maximum speed of rotation is 2 to 4 times the rated value. Winch drives using arine frequency converters will exhibit improved control and optional features using arine frequency converters with Vector Control since the exact control of speed and torque from n = 0 throughout the total speed range is guaranteed. For most winches, the arine frequency converter will be equipped with the technology board fitted with an application-oriented software. Among other things, the technology board takes care of all the superior speed and torque control as well as of the control of the holding brakes. It also continuously supervises the brake momentum versus the desired rotational speed. 11

12 LV Switchgear Emergency Stop Winch interface Frequency converter PROFIBUS Windlass control system otor interface Electric motors Winch Principal sketch of a winch control (Winch) Windlasses on a Hopper dredger 300 kw With arine frequency converters, electrical braking can be performed as follows: The electrical braking energy is fed back to the mains. The precondition is that the mains is able to receive the superfluous electrical energy, i.e. other heavy loads must be connected. The electrical braking energy is absorbed by a brake resistor. With braking of long duration, this will lead to a lot of heat being dissipated from the resistor, requiring more space than the previous braking option. Warp speed [%] Hydraulic drive 50 Electric drive Torque [%] Comparison between features of hydraulic drives and arine frequency converter controlled motor by winch application In conjunction with arine frequency converters, the controllability requirements for winches are analogous to those for cranes, be it grab cranes or container cranes. On a crane, there are often many motor drives, like for instance for the main hoist, an auxiliary hoist, gantry movements and transverse movements. Considering power load and the simultaneity factors, the most compact configuration of the arine frequency converter system would be to use a common mains rectifier feeding all converters via a DC busbar. The rectifier may well be of the feedback-of brake-energy type or with a common brake chopper mounted on the DC busbar. The DC busbar will then work as an energy smoothing connection. arine frequency converters for thrusters Bow Thrusters have until now mostly been equipped with hydraulic systems. This hydraulic system contains a fixed speed motor driving the thruster with a fixed speed, the water flow itself is controlled by changing the pitch of the propeller through the hydraulic system. With the arine frequency converters, the speed of the thruster can be changed in a wide range where the pitch is fixed. In other words, the water flow by the thruster is controlled by the speed of the motor. The complete control of the thruster is part of the arine frequency converter. For the steer able thruster, the arine frequency converter is also an optimal solution. Both movements (rotating and speed control of the thrusters) can be controlled by the drive. 12

13 arine frequency converters in fans and cooling systems On board most ships, there are a great number of pumps serving multiple purposes. Cooling water pumps are especially dimensioned to have their rated capacity at a water temperature of 32 C or 38 C. When operating in cooler seas, this means that unnecessary high volumes of cooling water are pumped through the systems, resulting in high cost of energy and wear of the mechanical equipment. Vessels used for instance for transporting fruit require very stable temperatures. In passing through climatic zones with changing temperature conditions, a arine frequency converter controlled cooling system will ensure constant storage room temperature. On board passenger and cruise vessels, considerable energy is used for ventilation and air conditioning. Day cycles and changing environmental temperatures mean the motor power requirement for systems of this kind will undergo large variations. With temperature control, only the required motor power will be used to maintain the desired temperature. For supply vessels, the ballast pumps, cargo pumps for fuel, brine and mud, etc. are installed with speed regulation using arine frequency converters. The use of arine frequency converters in regulating engine room temperature has also proved to provide great savings in energy. ost pump and fan systems pay for themselves within a couple of months of operation through energy saving. The operational advantages of reduced wear and maintenance come in addition to this. The first figure above shows the principal conditions in a temperature-controlled pump. The temperature behind the pump is measured using a transducer giving a 4 20 ma output signal. The arine frequency converters have integrated PID regulators which may be used for controlling temperature, volume, pressure levels, etc. In the given figure, the desired temperature is entered as a 0 10 V, 0 20 ma or 4 20 ma signal. The arine frequency converter controller will cause the AC motor to rotate at the speed needed to achieve the desired temperature. Supply vessel converter drives for cargo pumps, seawater cooling pumps and ventilation on board Required temperature 4-20 ma PID Temperature signal 4-20 ma Temperature regulation of a pump with arine frequency converter Required pressure 4-20 ma PID easured pressure 4-20 ma Pump control with arine frequency converter, pumps working in parallel with only one speed-controlled machine For two or more pumps or compressors working in parallel, only one machine will actually have to be speed-controlled whereas the others may be directly engaged or disengaged from the mains. In such cases, the arine frequency converters are equipped with application software. This software completely controls and supervises both the arine frequency converters and the pumps operated directly from the mains. When the arine frequency converter operates its controlled motor at maximum speed and there is a need for a still higher volume or pressure, the arine frequency converter will switch the next motor directly on line. The arine frequency converter will now automatically reduce the speed of its controlled motor during the acceleration process of the directly engaged motor, thus preventing pressure jolts and oscillations in the piping system. 13

14 arine frequency converters for other applications The arine frequency converter drives can also be used for other applications such as cranes and conveyor belts. Especially where speed or torque-controlled drives are necessary, the marine drives are at their best. With the open software functionality, customized applications can be easily adapted in the arine frequency converter by using this open software. = ain switchboard 3AC 380 / 690 V, 50/60 Hz DC Busbar = = = = ain lift Swing Portal Braking chopper Principal sketch of a arine frequency converter for a crane 14

15 Energy saving Within the ship industry, fuel consumption is an important part of operational costs. Especially when oil prices are rising, the fuel consumption of the vessel will get a more important priority within these costs. Energy saving is then an attractive way to reduce the fuel costs of a vessel. With Siemens arine frequency converters, a substantial amount of energy can be saved, especially in partial loads at pumps and fans. Shown below is a comparison between pump operation with throttle valve control and with variable speed control. Pump characteristic with throttle valve control The pump can deliver the amount of energy E given by the pump characteristic (blue) while the plant (i.e. cooling or heating circuit) needs only the energy shown by the plant characteristic (red). The energy difference (red arrows) has to be throttled away = wasted. The energy consumption at the input is approx. the same, throttle valve means mechanical control at the output. Pump head H [m] Other Issues Throttle valve control along pump characteristic (blue) *) Operation point Q = 400 m 3 /h at 150 m Q max = 450 m 3 /h Available power in operation point *) To despense ( throttle away ) = 160 m! Flow Q [m 3 /h] Energy E / Pump head H Pump characteristic with speed control Power P n = n A Flow Q The pump can due to variable speed n which means variable/controlled flow Q deliver the amount of energy E which is in every moment necessary in the process/plant. No energy difference has to be wasted. The energy consumption E at the input follows the speed control, i.e. it decreases with the speed reduction. Speed control means electrical control at the input. n = n A Energy E / Pump head H Q min Q A Q max Flow Q n = n A n 1 < n A Legend Blue: pump characteristic Red arrows: energy throttled away Red: process characteristic Black: power consumption n 2 < n 1 n 3 < n 2 The following graph shows the pump characteristic (blue) and the various regimes of the plant/process (red), regimes achieved using the throttle valve control. The energy waste is materialized by the pump head difference which is not used. Example: necessary flow 200 m 3 /h: necessary Q = 200 m 3 /h at 50 m (equiv. potential energy), but the pump can give 200 m 3 /h at 210 m (equiv. potential energy), results = 160 m wasted pump head, in other words this means 160 m wasted equiv. potential energy (see graph right above). Power P n Q A Q max Legend Blue: pump characteristic Red: process characteristic Black below: power consumption at various speeds n 4 < n 3 Flow Q Flow Q 15

16 Pump head H [m] Speed control: along plant/process characteristic (red) Siemens arine can support you with the calculation of the amount of energy saved see graph below: Electrical power P el [kw] The shaded area represents the energy saved due to the variable speed i.e. speed control Black: energy consumption with throttle valve control Red: energy consumption with speed control n Flow Q [m 3 /h] Operation point Q = 400 m 3 /h at 150 m Q max = 450 m 3 /h Available power in operation point Flow Q [m 3 /h] To limit the interference emissions of arine frequency converters, the following measures have to be taken: Interference suppression filters to limit conducted emissions. The arine frequency converters are equipped with filter components to reduce the conducted emissions according to the standard EN for Industrial Environment and in accordance with the specifications of the ship classification societies like DNV, GL, LR, ABS and BV. Shielded motor cables to reduce radiated emissions. This precaution has to be taken when installing the drive system. Compliance with the installation guidelines. This part is delivered together with the operating instructions of a arine frequency converter. To ensure the immunity of arine frequency converters, the following measures have to be taken: Shielded signal cables to protect the wires connected to the controller against electromagnetic interference. This precaution has to be taken when installing the drive system. Compliance with the installation guidelines. This part is delivered together with the operating instructions of a arine frequency converter. When all these measures are taken, the arine converters are operating reliably without interfering with other equipment in the same environment. The same effect will be with application with a constant torque characteristic such as reciprocal compressors. Electromagnetic compatibility (EC) The electromagnetic compatibility according to the definition of the EC directive defines the capability of a device to operate satisfactorily in an electromagnetic environment without itself causing electromagnetic interferences which would be unacceptable for other electrical devices in this environment. In order to ensure that the relevant EC standards are complied with, interference emissions must be limited to compatible values on the one hand, and the devices must achieve a sufficient level of immunity on the other hand. arine frequency converters are producing electromagnetic emissions in their power sections by switching on and off high electrical voltage very fast. This creates emissions which are conducted to the environment by the connected power cables and radiated to the environment by air. These emissions must be limited. The controller and other electronic components of arine frequency converters consist of very sensitive electronic devices which must be protected against electromagnetic interference. 16

17 Harmonic currents and tuned filter circuits All power electronic units where diodes and thyristors are used will cause distortion of the mains voltage. Thyristor rectifiers will in addition cause considerable inductive reactive currents. The rectifier current consists of a multitude of sine-shaped currents, a basic frequency component and a lot of harmonic currents of frequencies several times that of the mains frequency. The network impedance will cause all these currents to generate voltages superimposed on the fundamental sinusoidal wave form of the mains. This leads to distortion of the mains voltage which may give rise to mains faults and fall-out of other subscribers. The mains rectifier loads the network with the basic frequency I 1 and returns to the network (power line) currents with harmonic numbers v v = 6. k + 1, k = 1, 2, 3,... 0 I(5) I (7) U phase Decomposition of the rectifier current into basic and harmonic components The filter circuits may be connected directly to the low voltage side to keep higher harmonic currents away from the mains network. The filter circuits consist of capacitors in series with a coil (inductor). The resonance circuits are tuned to give approximately zero resistance to each of the harmonic components. Thus, the major parts of the harmonic currents are absorbed by the filter circuits. Only tiny parts of the unwanted currents will return to the mains network, causing only a negligible distortion of the mains voltage. As seen from the mains (50 Hz or 60 Hz), the filter will appear as a capacitive impedance. This means that the filter circuits will not only absorb the harmonics but also conduct capacitive currents. They will therefore additionally act as reactive compensation for the complete network. With filter circuits, the harmonic currents may be reduced to a maximum of up to 90 %. Sensitive equipment of other types may not be connected to the network unless separated by a transformer. I L I (1) edium voltage network Transformer Low voltage network Tuned filter circuit Absorption of harmonic currents in filter circuits As seen from the figure, the capacitance and inductance play crucial parts in the reduction of harmonics. This means that to avoid resonance, the inductivity of the network is important in the dimensioning of the filter circuits. The number of generators in operation will change the network inductivity, i.e. the short-circuit reactance of the network and the filter circuits must be dimensioned to cater for such operational situations as well. Harmonic distortion of mains supply All mains rectifiers used in DC and AC motor drives equipped with diodes and thyristors have the characteristic of drawing non-sinusoidal current form the mains. Consumption of this kind will thereby distort the mains voltage. The degree of distortion is known as the Distortion Factor (DF) The classification companies often require that THD (Total Harmonic Distortion) must be less than 5%, which must be taken into account when choosing a drive concept. The higher the total arine frequency converter power is relative to the generator power and its short-circuit power, the higher the distortion of the mains voltage. A network with high voltage distortion might damage other network components and lead to unexplainable fall-outs. arine frequency converters for small and medium power outputs are designed with so called 6-pulse mains rectifiers, i.e. with 6 diodes or thyristors used in the rectifier. The figure gives the current drain from a generator supply of a 6-pulse frequency converter, and also shows how this distorts the mains voltage. If such concepts are used for large consumers, the main source distortion may amount to something like 20 to 30%. 17

18 For higher motor powers (as seen in relation to the generator capacity), the arine frequency converters should be constructed with a 12-pulse rectifier, i.e. 2 times 6-pulse mains rectifiers connected to a separate supply system via a three-winding transformer. The transformer output (Dy5Dd0) group is arranged to give a 30 electrical phase shift between the two secondary winding systems. The connection to the pre-connected mains circuit will in this case result in a reduction of the mains voltage distortion. With two such arine frequency converter drives, the connection groups of the two transformers may be 15 phase shifted relative to each other. We have then obtained a so-called 24-pulse connection to the mains; however, in order to obtain the full reduction of the harmonic distortion, it is a condition that the two motor drive system are equally loaded. With their arine frequency converters, Siemens is having a complete type range of mains rectifiers using transistor technology (IGBT). In construction, this rectifier is identical to the frequency inverter. The advantage of transistors is their ability to be turned on and off. The arine Active Front End mains rectifiers are controlled in a way to draw an undistorted sine-shaped current from the mains. This means that the power factor is exactly equal to 1. However, the Active Front End rectifier may be parameterized if the power factor is required to deviate from 1. The value of the power factor may be parameterized to be either capacitive or inductive. This means that arine frequency converters with Active Front End mains rectifiers may take over the task of the generator to supply reactive power to inductive loads like for instance motors directly connected to the mains. The voltage distortion from an Active Front End is below 2%, which means that the distortion is not visible in the oscilloscope picture. For vessels with an amount of large consumers relative to the generator power at its maximum, the Active Front End is the ideal solution. This is true both with respect to price and space requirements, and the resulting low network distortion. The use of an Active Front End will make a clean power machine superfluous, e.g. a rotating or static converter. The principal construction of arine frequency converters as 6-pulse, 12-pulse and as Active Front End with the associated network current loads 6-pulse rectifier 12-pulse rectifier Active Front End arine frequency with three possibilities for Bus communication The digitalization of control and regulation facilities provides potentials for new possibilities. arine frequency converters may be connected to automation systems via serial interfaces and data bus systems. Parameters from arine frequency converters may then be exchanged with those from an automation system for process control (scale values, actual values, commands and messages), for process adaptation (control set points, choice of curve characteristics) and for service cases (stored fault messages, times of operation, measured and calculated process parameters). The quality of the data interface, the structure and content of parameters as well as the operational and service philosophy form parts of the essential quality properties of a speed-controlled motor drive. Communication with PROFIBUS arine frequency converters may be connected to the PROFIBUS system standardized by DIN Other components are also available, like actuators, valves and sensors connectable to the PROFIBUS standardized bus system. All information previously connected to the arine frequency converter via the conventional I/O terminal block may now be transferred via the bus system on a two-wire cable. The automation system delivers its commands and scale values through the cable in the form of telegrams. Status reports and actual values run in the opposite direction for possible presentation on a screen-based control system. PROFIBUS guarantees a quick and safe data transmission using the aster-slave principle. The high transmission rate of 1.5 bit/sec and the short reaction time enables transmission periods of less than 1 ms to and from the automation system (the master) for instance connected to a arine frequency converter (a slave). Communication between drives by Siemens DRIVE-CLiQ When operating cranes and winches where one motor drive is mutually dependent on the operation of other drives, much equipment and planning may be saved by letting the motor drives communicate directly with each other. This fast connection may convey information of changes in both speed and torque to the other motor drives. The signaling between drives is extremely fast due to the fact of the Ethernet communication. This fast communication may be made with or without PROFIBUS. When PROFIBUS is used, non-time-critical information can be handled over this communication net, the time-critical information over the DRIVE-CLiQ bus. In this way, more time-critical information can be handled.

19 Commissioning and service with a Personal computer For the arine frequency converters powerful service tools are available. STARTER is a tailor-made visualization program for commissioning and service, creating figures and text to aid you safely through implementation. Having put the arine frequency converter into service, STARTER may be used for easy adjustments of parameters and functions. Having commissioned or made the necessary changes in parameters, the complete content of the arine frequency converter parameter memory may be stored in a PC. This will be a safe back-up and may come in useful when the day comes for replacing the arine frequency converter or its control board. You will then only have to transfer the complete set of stored parameter data from the PC. STARTER also has an oscilloscope function where up to six physical values, for instance current, rotational speed, torque, etc. may be simultaneously measured on the PC. The dynamic load limitation system will continuously adapt and limit the power consumption to the generators' maximum load. Enabling the complete electric system, and particularly the generators, to be run according to their nominal loads, no other control system is needed to ensure the reliability of the power supply on board. If one diesel generator has an unexpected sudden shutdown, the DLL system will immediately react. The power consumption of the heavy consumer system will, within 160 ms, be reduced and kept within the nominal load limits for the remaining generators. The dynamic load limitation system is so fast that a black-out is avoided. The dynamic load limitation system is an option in the arine frequency converter and is independent of the Power anagement System (PS). Dynamic load limitation (DLL) Siemens philosophy is that a heavy load drive system with its generators, main switchboards, arine frequency converters and motors is one system even with respect to dynamic load changes. Due to the largest consumers, it is of vital importance that this consumer is not able to overload the generator, or in a worst-case scenario, cause a black-out in the electric system. Such a large consumer with arine frequency converters can be equipped with a dynamic load limitation system. This is a control system which continuously limits the power consumption of the heavy consumer drive according to the actual, available generator capacity. Royal Carribean International: Radiance of the Seas In case of electric propulsion and the dynamic load limitation option, the arine frequency converters are also adapted to the dynamic behavior of the propeller. The arine frequency converters ensure that the power oscillation of the propellers in heavy sea does not result in power oscillations in the generators and on the main bus. All these important characteristics of the arine frequency converters and the dynamic load limitation system enable the heavy consumer drive to act as a small consumer in the ship's electric system. Load [%] Load on generators Time [ms] Drive output power Dynamic load limitation: Power reduction of the drive when available generator power is suddenly reduced by 50% 19

20 Summary Royal Carribean International: Radiance of the Seas The main customer benefits and important characteristics of the arine frequency converter are: Easy to order, order specific documentation, fast logistics and worldwide service Universal operation, Engineering and Service of the equipment PROFIBUS Interface for easy implementation in higher-ranking automation systems Easy integration into existing installations, compact with small erection area needed Low noise level Standard and compact cabinet in IP22 and IP54 in air and water cooling Easy commissioning, for standard applications only few parameters have to be adjusted Easy operation through menu-guided control panel with graphic-supported plain text display Excellent serviceability Special security concept for protection against unintentional or unauthorized calibration changes Encoder-free Vector Control for robust and reliable operation Siemens AG Automation and Drives Large Drives, arine Equipment Postfach NÜRNBERG FEDERAL REPUBLIC OF GERANY Tel Fax The information provided in this brochure contains merely general descriptions or characteristics of performance which in actual case of use do not always apply as described or which may change as a result of further development of the products. An obligation to provide the respective characteristics shall only exist if expressly agreed in the terms of contract. Order No.: 6ZB5731-0AB02-0BA0 Printed in the Federal Republic of Germany 18402/ Vog