Designing with AMPHION 28VDC Solid State Power Controllers

Transcription

1 Designing with AMPHION 28VDC Solid State Power Controllers AMPHION Solid State Power Controllers (SSPC) can be used to replace relays or Remote Control Circuit Breakers in most avionics applications, especially where a significant amount of load and wire protection is desired. The SSPC offers better load protection features than a circuit breaker, works like a super fast relay, and is packaged in a relay sized plug-in enclosure. The SSPC can be combined with other AMPHION components into a power distribution system, or be used as a relay replacement in any 28VDC application. This paper presents an overview of: AMPHION SSPCs and Evaluation Board The features and capabilities of the AMPHION SSPC. Information on some real world applications. Lighting Control Motor Control Heater Control Secondary Power Distributionj Connection to and control of the AMPHION SSPC. Avionics 900 Clymer Avenue, Sellersville, PA TEL: FAX: Contact: Fred Potter, Engineering Manager ext. 1343; fred.potter@ametek.com 2002 by AMETEK, Inc. rev.03/02 All rights reserved.

2 Low Loss Solid State Design Amphion SSPCs have a very low on resistance, typically less than Ohms, so they have no special heatsinking or cooling needs. The resistance stays at this low level over many years, unlike mechanical contacts that age and eventually wear out and fail. The SSPC also has little sensitivity to temperature variation or vibration, and will perform consistently and reliably within its rated operating environment. Unlike other solid state products, the AMPHION SSPC contains patented circuitry that prevents a failure in a short-circuited condition. This means that a SSPC failure will not cause a critical load to remain powered in an unprotected and uncontrolled manner. The AMPHION SSPC has no mechanical contacts, so there are no contacts to burn away, wear out, or weld shut. Unlike electro-mechanical relays, there are no relay drivers required, and no significant control circuit power consumption to worry about. AMPHION Connection Diagram AMPHION SSPCs are easily interfaced into control circuitry at different levels of technology. On, off, and reset functions are all initiated by a momentary connection to ground. This system performs equally well with switches and analog circuitry as it does with microprocessor based systems. Top View 28VDC Supply 28VDC Input 28VDC Input 28VDC Output 28VDC Output Open Collector type gate Surge Trip N ominal Trip Default Strap LOAD /RESET /TRIP Power Common SPI Open Collector type gate Small Size This chart shows the size of each member of the AMPHION SSPC family. The diagram below shows the PCBA layout for each size module. Notice that a large module can not plug into a smaller socket. Part Number Current Range Size Weight 10676B01E to 1 A W x T x 0.44 H 0.6 oz B01E03 1 to 3 A W x T x 0.44 H 0.6 oz B01E05 1 to 5 A W x T x 0.44 H 0.6 oz B01E10 5 to 10 A W x 1.00 T x 0.50 H 1.0 oz B01E15 10 to 15 A W x 1.00 T x 0.50 H 1.0 oz B01E20 15 to 20 A 1.35 W x 1.35 T x 0.50 H 1.0 oz B01E25 20 to 25 A 1.35 W x 1.35 T x 0.50 H 2.0 oz B01E30 25 to 30 A W x 1.75 T x 0.52 H 2.0 oz.

3 Surge set SDO Overload set SDI Reset SClk Trip CS-IV Gnd CS-T & 30A size 15 & 20A size 5 &10A sizes 3A size Arc Fault Protection The AMPHION SSPC contains arc fault protection circuitry that will detect and trip on intermittent arcing in the load or wiring. The arc fault detector detects the fault current pattern typical of an arc and is not fooled by normal inrush surges or other types of current peaks. Programmable Trip Characteristics The curves below show the programmable trip characteristics of a typical AMPHION arc detecting SSPC compared to the typical 25 C characteristic of a thermal circuit breaker % Rated Current Trip Tim e in Se conds Arc Fault SSPC Slow Trip Thermal CB A rc Fault SSPC Fast Trip

4 The resistor programmable feature of the AMPHION SSPC makes it very easy to tailor the trip characteristics to the load, enabling the best possible load and wire protection without increasing the number of false trips. The AMPHION SSPC does not use software to set or shape the trip curves, so the fault protection of the SSPC is not effected by failures in the host system.

5 Replacement of Relays/Circuit Breakers with AMPHION SSPCs A Lighting Power Distribution and Control System This diagram shows a lighting control system implemented with AMPHION 28VDC SSPCs. SPI Data In SPI Data Out SPI Clock SPI Enable #1 SSPC#1 /Trip SSPC#1 /Reset 28 VDC Lamp Load(s) AMPHION SSPC #1 SPI Data In SPI Data Out SPI Clock SPI Enable #N SSPC #N /Trip SSPC #N /Reset 28 VDC Lamp Load(s) AMPHION SSPC #N Microprocessor Based Controller Aircraft Data Data from other aircraft systems is received by the Controller and used to turn on and off the lights. If light dimming or a soft start for the lighting loads is required, the AMPHION SSPCs are fast enough to provide PWM modulation to the loads ( Hz, applying a reduced Voltage to dimmed lamps or a ramp up to full Voltage as the lamps warm up. The controller may also report back on load status (on off burned-out - tripped) as part of an aircraft maintenance system. A very important point to note here is that the AMPHION SSPCs eliminate the need for any additional light dimming, blinking, or monitoring systems. Also eliminated are the need for individual circuit breakers for each lamp load, as the AMPHION SSPC offers all the load and wire protection that is needed. This system can be designed to work with any aircraft data bus, and offers load control, load and wiring fault protection (no extra circuit breakers or fuses) and provides status feedback.

6 A Heater Power Distribution and Control System This diagram shows a heating control system implemented with AMPHION 28VDC SSPCs. It is identical in hardware and software to the lighting system shown earlier, it differs only in the types of loads and the control inputs that it responds to. SPI Data In SPI Data Out SPI Clock SPI Enable #1 SSPC#1 /Trip SSPC#1 /Reset 28 VDC AMPHION SSPC #1 Windshield Heater SPI Data In SPI Data Out SPI Clock SPI Enable #N SSPC #N /Trip SSPC #N /Reset 28 VDC AMPHION SSPC #N Pitot Heater Microprocessor Based Controller Aircraft Data Temperature Sensors Data from temperature sensors or from other aircraft systems is received by the Controller and used to turn on and off the heaters. The controller may also report back on load status (on off burned-out - tripped) as part of an aircraft maintenance system. A very important point to note here is that the AMPHION SSPCs eliminate the need for any additional circuit breakers, relays, or monitoring systems. as the AMPHION SSPC offers all the controllability, monitoring, load and wire protection that is needed.

7 Fuel Management (A Motor/Valve Control System) This diagram shows a motor and valve control system implemented for a fuel management system with AMPHION 28VDC SSPCs. It is identical in hardware and software to the lighting system shown earlier, it differs only in the types of loads and the control inputs that it responds to. SPI Data In SPI Data Out SPI Clock SPI Enable #1 SSPC#1 /Trip SSPC#1 /Reset 28 VDC AMPHION SSPC #1 Fuel Pump SPI Data In SPI Data Out SPI Clock SPI Enable #N SSPC #N /Trip SSPC #N /Reset 28 VDC AMPHION SSPC #N Fuel Valve Microprocessor Based Controller Aircraft Data Temperature Sensors Data from tank level sensors or from other aircraft systems is received by the Controller and used to turn on and off the valves, pumps, or motors The controller may also report back on load status (on off burned-out - tripped) as part of an aircraft maintenance system. A very important point to note here is that the AMPHION SSPCs eliminate the need for any additional circuit breakers, relays, or monitoring systems. as the AMPHION SSPC offers all the controllability, monitoring, load and wire protection that is needed.

8 A Secondary Power Distribution System A typical AMPHION SSPC based 28 VDC power distribution system is shown below. GCU Starter Generator #1 Starter Generator #2 GCU Shunt DC #1 BCU Charger DC #2 Emerg. #1 Emerg #2 SSPC SSPC SSPC SSPC SSPC SSPC SSPC SSPC SSPC Power Control System containing multiple SSPCs Load #1 Load #2 Load #n * * * * * * A microprocessor based controller in the system interfaces with a load control panel (replacing the conventional circuit breakers) and can communicate load status (on off inoperative Voltage Current) to a central maintenance computer. Because of the speed of the SSPCs and the complete lack of failure mechanisms, the power distribution system can replace many other aircraft systems such as heater temperature controllers, light dimming/blinking systems, and even motor and pump controllers.

9 Controlling the AMPHION SSPC The AMPHION SSPC is easy to control; it works much like a conventional latching relay or JK flipflop. The circuit in Figure 1shows how an AMPHION SSPC would be connected to control a typical load. Open Collector type gate 28VDC Supply Surge set SDO Overload set SDI Reset SClk Trip CS-IV Gnd CS-T LOAD SPI Open Collector type gate Figure 1 AMPHION SSPC Connections Pin Connections The /Trip and /Reset Pins These pins are internally pulled up, and are designed to be used with mechanical switches, transistors, or open collector types of electronic devices. The pull down must be to less than 1V. /Trip Pulling this pin to ground turns the SSPC off. The SSPC responds to this input identically as to an overcurrent trip condition, turning off within 10 us. /RESET (on-off) Input This pin shall be connected to open collector type drivers without pull-up resistors to any Voltage. The driver used with this input shall pull down to 0.5V (max) from SSPC ground. Minimum reset pulse time is 1ms. Reset of the SSPC shall occur when the /RESET pin returns high. The /RESET pin shall also turn off the SSPC when asserted (ground), allowing for a single pin control scheme. The SPI Pins The SSPC has a programmable A/D converter that can be used to read current or Voltage. It communicates over a 4 wire SPI bus. The details and protocol are briefly explained below. More detailed information is available in the LTC1298 datasheet, available from Linear Technology Inc: Input signal levels on these pins must be TTL compatible.

10 Device Select-CS-IV This pin is pulled to ground to select the SSPC for SDI data transfer of output current or Voltage. It must be externally pulled up to +5V. Device Select-CS-T This pin is pulled to ground to select the SSPC for SDI data transfer of trip status. It must be externally pulled up to +5V. Serial Data Clock This pin accepts a clock signal from an external device. The maximum recommended clock frequency is 200kHz. Serial Data This pin accepts clocked serial data from an external device, or provides serial data to an external device. Serial Data Out This pin accepts clocked serial data from an external device.

11 Programming the Over-current Trip Capability The SSPC features a fully adjustable time vs. current trip characteristic and has the ability to detect and trip on intermittent arcs produced by wire insulation failure. In order for the SSPC to discriminate between legitimate surges and faults, the over-current trip characteristics must be set to match the characteristics of the load. The AMPHION SSPC has two external resistors that are used to customize the set points for each load. One, called the Instant Trip set point, sets the maximum allowable normal surge. The other, called the Normal Trip set point, sets the maximum allowable normal operating current. Surge Set To set the SSPC surge trip setpoint, the maximum surge or inrush current for the load must be determined, and then the Instant Trip resistor set from the graph below Amp 2 Amp 3 Amp 4 Amp 5 Amp 6 Amp 7 Amp 8 Amp 9 Amp 10 Amp 11 Amp Figure 2 Instant (Surge) Trip Resistor K Ohm Resistance

12 Normal Set To set the SSPC normal trip setpoint, the absolute maximum normal operating current for the load must be determined (plus some safety margin), and then the Normal Trip resistor set from the graph below K Ohm Resistance Amp 1 Amp 2 Amp 3 Amp 4 Amp 5 Amp Figure 3 Normal Trip Resistor