Speed Control Speed Control Brushless Motor's Structure and Principle of Operation Structure of Brushless Motor Ball Bearing Shaft Brushless motors have built-in magnetic component or optical encoder for detecting the rotor position. Each position detector sends signals to the drive circuit. Motor windings are based on three-phase star wiring. The rotor uses permanent magnets. Structure of Brushless Motor =Phase- inding Stator =Phase- inding =Phase- inding Rotor=Magnet Rotor S N Rotor Hall Effect IC Stator N S Switching Sequences of Individual Transistors Step Transistor 1 2 3 4 5 6 7 8 9 1 11 12 13 Tr1 ON ON ON ON ON Tr2 ON ON ON ON Tr3 ON ON ON ON Tr4 ON ON ON ON Tr5 ON ON ON ON Tr6 ON ON ON ON ON Phase N S S N N S S N N Phase N N S S N N S S Phase S S N N S S N N S Control Method of Brushless The drive circuit of a brushless motor is connected to the motor and mainly consists of five blocks according to the structure shown in the figure. Power circuit Current control circuit Logic circuit Setting comparison circuit Power supply circuit M Brushless Motor Power circuit Logic Circuit Current Control Circuit Setting Comparison Circuit Power supply circuit Motor inding Start/Stop Brake/Run C/CC Speed Setting H.E H.E H.E Hall Effect IC + Output 1 Output 2 Output 3 Power circuit Current flowing through the motor windings is controlled. Six transistors are used. The transistors connected on top and below are turned ON-OFF repeatedly according to a specific order to cause current to flow through the motor windings. The detection magnetic component uses a Hall effect IC. Three components are provided on the inner side of the stator and as the rotor turns, each Hall effect IC outputs a digital signal. Drive Method of Brushless The motor windings are connected to switching transistors, where six transistors constitute one inverter. The upper and lower transistors are turned ON-OFF alternately and repeatedly according to a specific order to change the direction of current flowing through the windings. The mechanism of how the rotor turns is explained. Based on the transistor switching sequence shown in the figure below, transistors Tr1 and Tr6 are ON in step 1. In this condition, current flows from phase to phase through the windings, with phase and phase excited to the N pole and S pole, respectively. This causes the rotor to rotate by 3. hen this operation is repeated 12 times, the rotor turns by one rotation. 1 Motor inding 2 3 Tr1 Tr4 Power circuit Tr2 Tr5 Tr3 Tr6 + Current control circuit The current flowing through the motor changes depending on the load size. The current flowing through the motor is constantly detected and controlled so that the actual speed will not deviate from the set speed. Logic circuit Feedback signals are received from the motor's hall effect IC to detect the rotor position and determine the excitation order of motor windings. These signals are connected to the base of each transistor in the power circuit, to drive the transistors according to a specific order. They are also used to detect the motor speed. In addition, these signals are used to control such motor commands as Start/ Stop, Brake/Run and C/CC. Setting comparison circuit Compare the speed setting signal and motor speed signal. The result is used to check whether the motor speed is higher or lower than the set speed. If the motor speed is higher than the setting, the input to the motor is decreased until the setting speed is restored. If the motor speed is lower, the input to the motor is increased until the setting speed is restored. Power supply circuit The power supply circuit is used to convert the commercial power supply to the voltage needed to drive the motor and each control circuit. H-4
Technical Reference Speed Torque Characteristics of Brushless The figure below shows an example of characteristics of the BLE Series. The characteristics of the AX Series, BX Series and BLH Series are roughly the same, although the speed control range is different. ith brushless motors, the rated torque and starting torque are constant in a range from 1 to 4 r/min (for the BLE Series and BLH Series, the output torque at the maximum speed becomes lower than the rated torque), as shown in the example below. Therefore brushless motors can be used at their rated torque over the entire speed range from low to high without experiencing a torque drop at low speed which is often seen with AC speed control motors. Brushless motors have a limited duty region in addition to a continuous duty region. In the limited duty region, the generated torque corresponds to twice the rated torque (1.2 times the rated torque in the case of the AX Series and BLH Series), which is very useful when starting an inertia load. Note that when operation is continued for 5 seconds or more in the limited duty region, the driver's overload protective function will actuate to cause the motor to stop naturally. Torque [N m] Speed Torque Characteristics.4.2.15 1 Starting Torque Limited Duty Region Continuous Duty Region BLE46C S BLE46C F BLE46CA 1 2 3 Speed Control Method of Speed Control 4 A basic block diagram illustrating the control method is shown below, accompanied by an overview of the control method. AC speed control motors adopt the closed-loop speed control method, while inverters adopt the openloop speed control method. AC Speed Control Motor Control Method 1 Speed setting voltage is given from the speed potentiometer. 2 The motor speed is detected to give the speed signal voltage. 3 The difference between the speed setting voltage and speed signal voltage is output. 4 The voltage needed to achieve the set speed is calculated according to the output from the comparator and given to the motor. Motor Tachogenerator Generated oltage Characteristics of Tachogenerator The tachogenerator directly coupled to the speed control motor generates AC voltage roughly proportional to the motor speed, as shown in the figure below. Accordingly, the motor speed can be calculated by connecting an AC voltmeter between the tachogenerator leads. (For the AC voltmeter, use a unit whose internal impedance is 2 kω or more. Oriental Motor offers a dedicated tachometer as an accessory.) Speed Indicators Page B-154 35 oltage Generated by Tachogenerator [ac] 3 25 2 15 1 5 5 1 15 2 Motor Motor Speed Tachogenerator Generated oltage Characteristics (S Series) Inverter Control Method 1 The input from the AC power supply is rectified and DC voltage is output. 2 A signal indicating the voltage that matches the frequency set by the frequency setting potentiometer is output. 3 oltage of the set frequency is applied to the motor. 3 1 Motor Inverter Converter Power Supply 2 LO Inverter Frequency Setting Potentiometer HIGH oltage/frequency Control Circuit Selection Calculations Service Life Standard AC Speed Control Stepping Servo Gearheads Linear Heads Capacitor 4 2 Speed Controller oltage Control Circuit 3 Comparator 1 Speed Potentiometer Power Supply CAD Data, Manuals Technical Support Please contact the nearest Oriental Motor sales office or visit our ebsite for details. H-41
Speed Control Speed Torque Characteristics of Speed Control AC Speed Control In general, AC speed control motors have the speed torque characteristics shown in the figure below. Speed Torque Characteristics MSC-1/4IK25 Type Torque [N m].4.3.2.1 Permissible Torque hen Gearhead is Attached Starting Torque 5 Hz Safe-Operation Line 6 Hz Safe-Operation Line 5 Hz 6 Hz 9 5 1 14 16 Load Factor and Speed Ratio Let us consider the relationship of load factor and speed ratio. hen a motor is actually used, it is often combined with a gearhead. Accordingly, the following explanation also uses an example where a motor is combined with a gearhead. The table below shows the continuous duty regions and speed ratios of the S Series at load factors 2% and 5% based on readings from the graph. The speed ratio can be increased when the load factor is 2%, but the ratio becomes small at 5%. As these figures show, generally AC speed control motors cannot be operated across a wide range. To increase the range of operation, select a motor that has a larger starting torque (motor of the next larger frame size). This is not the case with brushless motors though, as brushless motors can be operated over a wide range as shown by the dotted lines. <Speed Torque Characteristics> S59-512/5G5KB 4. S59-512+5G5KB AX59C-G+5G5KB Inverters In general, inverters have the speed torque characteristics shown in the figure below. ith inverters, the speed is changed by changing the frequency of the voltage applied to the motor. Consequently, the speed also changes according to the load torque just like the characteristics of induction motors. Speed Torque Characteristics Inverter/4IK25GN (A) -S2.4.3 Torque [N m] 3. 2. 1.8 1. Load Factor 5% 1:2 Load Factor 2% 1:2 1 2 3 4 Torque [N m].2.1 5 1 15 2 25 Permissible Torque 1 2 3 4 5 6 7 8 Setting Frequency [Hz] Safe-Operation Line and Permissible Torque hen Gearhead is Attached ith speed control motors, the input changes according to the load and speed. The larger the load or the lower the speed, the higher the temperature will rise. Speed torque characteristics graphs of AC speed control motors and inverters indicate the "safe-operation line," and the area below this line is called the continuous duty region. The safe-operation line, measured by motor's temperature, indicates its limit for continuous operation (3 minutes operation for a reversible motor) with the temperature level below the permissible maximum temperature. hether or not the motor can be operated at the actual load and speed is judged by measuring the temperature of the motor case. Given the insulation class of the windings, generally continuous operation is possible as long as the motor case temperature is 9 C or less. Note, however, that the lower the motor temperature, the longer the motor will last. Accordingly, we recommend that you use the motor under conditions where its temperature will remain low. If a gearhead is used, make sure the "permissible torque when gearhead is attached" will not be exceeded. If a gearhead is used and the motor is operated at torques beyond the aforementioned torque, the life of the motor may be shortened or the motor may be damaged. ariable Speed Range (Speed Ratio) and Load Factor hen the speed ratio is defined as the ratio of the minimum speed and maximum speed in the variable speed range of an AC speed control motor, the speed ratio becomes as high as 1:15 in a range where the load factor (ratio of the load torque relative to the starting torque) is small (load factor of 4% in the figure below), thereby expanding the scope of operation. On the other hand, the speed ratio becomes low when the load factor is large. Load factor [%] Minimum Speed Continuous Duty Region Maximum Speed Speed Ratio 2 17 348 1:2 5 148 337 1:2 Speed Ratio when sing a Gearhead of High Gear Ratio Since the starting torque is also limited by the maximum permissible torque of the gearhead, when a gearhead with a high gear ratio is used, the load factor corresponds to the load torque relative to the maximum permissible torque of the gearhead. In the above example, a gearhead of gear ratio 5 was used. Now, let's take a look at what happens when a gearhead of gear ratio 1 is assembled. Torque [N m] 3 2 1 S59-512+5G1KB AX59C-G+5G1KB 1:2 Load Factor 5% 1:19 Load Factor 3% 1:2 5 1 15 2 The maximum permissible torque of the gearhead 5G1KB of gear ratio 1 is 2 N m. The table below shows the speed ratios at load factors 3% and 5%. Load factor [%] Minimum Speed Continuous Duty Region Maximum Speed Speed Ratio 3.9 17.6 1:2 5.9 17.4 1:19 As shown, if a gearhead of high gear ratio is combined. the speed ratio can be increased without giving too much consideration to the load factor. H-42
Technical Reference Load Torque Driver Input Current Characteristics of Brushless (Reference values) ith brushless motors, the driver input current changes according to the load torque. The load torque is roughly proportional to the driver current. The load torque can be estimated from the driver input current based on these characteristics. These characteristics assume that the motor is running at a constant speed. These characteristics do not apply when the motor is started or changes its direction because greater current is applied. The values for combination types and geared motors apply to the motor only. Selection Calculations BLE Series BLE23A S-, BLE23A F- BLE23A A- 1.2.9.6.3.2.4.6.8.1 4 r/min 3 r/min 2 r/min 1 r/min 5 r/min 8 r/min BLE23C S-, BLE23C F- BLE23C A-.8.6.4.2 4 r/min.2.4.6.8.1 3 r/min 2 r/min 1 r/min 5 r/min 8 r/min BLE23S S-, BLE23S F- BLE23S A-.4.3.2.1.2.4.6.8.1 4 r/min 3 r/min 2 r/min 1 r/min 5 r/min 8 r/min Service Life BLE46A S-, BLE46A F- BLE46A A- 2. 1.6 1.2.8.4.5.1.15.2 4 r/min 3 r/min 2 r/min 1 r/min 5 r/min 8 r/min BLE46C S-, BLE46C F- BLE46C A- 1..8.6.4.2 4 r/min.5.1.15.2 3 r/min 2 r/min 1 r/min 5 r/min 8 r/min BLE46S S-, BLE46S F- BLE46S A-.6.4.2.5.1.15.2 4 r/min 3 r/min 2 r/min 1 r/min 5 r/min 8 r/min Standard AC Speed Control Stepping BLE512A S-, BLE512A F- BLE512A A- 3. 2. 1. AX Series.1.2.3.4 4 r/min 3 r/min 2 r/min 1 r/min 5 r/min 8 r/min BLE512C S-, BLE512C F- BLE512C A- 2. 1..5 4 r/min.1.2.3.4 3 r/min 2 r/min 1 r/min 5 r/min 8 r/min BLE512S S-, BLE512S F- BLE512S A- 1..8.6.4.2.1.2.3.4 4 r/min 3 r/min 2 r/min 1 r/min 5 r/min 8 r/min Servo Gearheads Linear Heads AX21A-GN AX21A-A.8.6.4.2 2 r/min 15 r/min 1 r/min 5 r/min 1 r/min AX21C-GN AX21C-A.4.3.2.1 2 r/min 15 r/min 1 r/min 5 r/min 1 r/min AX21S-GN AX21S-A.4.3.2.1 2 r/min 15 r/min 1 r/min 5 r/min 1 r/min.2.4.6.2.4.6.2.4.6 AX425A-GN AX425A-A 1.25 1..75.5.25 2 r/min 15 r/min 1 r/min 5 r/min 1 r/min AX425C-GN AX425C-A.8.6.4.2 2 r/min 15 r/min 1 r/min 5 r/min 1 r/min AX425S-GN AX425S-A.8.6.4.2 2 r/min 15 r/min 1 r/min 5 r/min 1 r/min.5.1.15.5.1.15.5.1.15 A number indicating the gear ratio is specified in the box in the product name. For the electromagnetic brake type, M is entered where the box is located within the product name. A number indicating the desired length of 1 (1 m), 2 (2 m) or 3 (3 m) for the cable included with the product is entered where the box is located within the product name. CAD Data, Manuals Technical Support Please contact the nearest Oriental Motor sales office or visit our ebsite for details. H-43
Speed Control AX54A-GN AX54A-A 2. 1..5 2 r/min 15 r/min 1 r/min 5 r/min 1 r/min AX54C-GN AX54C-A 1..75.5.25 2 r/min 15 r/min 1 r/min 5 r/min 1 r/min AX54S-GN AX54S-A 1..75.5.25 2 r/min 15 r/min 1 r/min 5 r/min 1 r/min.5.1.15.2.25 AX59A-G AX59A-A 2.5 2. 1..5 BX Series BX23A - S BX23A - FR BX23A -A 1..5 BX46A - S BX46A - FR BX46A -A 2. 1..5 BX512A - S BX512A - FR BX512A -A 4. 3. 2. 1..1.2.3.4.5 2 r/min 15 r/min 1 r/min 5 r/min 1 r/min.2.4.6.8.1.12 3 r/min 2 r/min 1 r/min 3 r/min 3 r/min.5.1.15.2.25 3 r/min 2 r/min 1 r/min 3 r/min 3 r/min.1.2.3.4.5 3 r/min 2 r/min 1 r/min 3 r/min 3 r/min.5.1.15.2.25 AX59C-G AX59C-A 2. 1..5.1.2.3.4.5 2 r/min 15 r/min 1 r/min 5 r/min 1 r/min BX23C - S BX23C - FR BX23C -A (Single-Phase 2-23 AC).8.6.4.2.2.4.6.8.1.12 3 r/min 2 r/min 1 r/min 3 r/min 3 r/min BX46C - S BX46C - FR BX46C -A (Single-Phase 2-23 AC) 3 r/min 1.25 2 r/min 1..75.5.25.5.1.15.2.25 1 r/min 3 r/min 3 r/min BX512C - S BX512C - FR BX512C -A (Single-Phase 2-23 AC) 3 r/min 2. 1..5.1.2.3.4.5 2 r/min 1 r/min 3 r/min 3 r/min.5.1.15.2.25 AX59S-G AX59S-A 1..75.5.25.1.2.3.4.5 2 r/min 15 r/min 1 r/min 5 r/min 1 r/min BX23C - S BX23C - FR BX23C -A (Three-Phase 2-23 AC).6.4.2.2.4.6.8.1.12 3 r/min 2 r/min 1 r/min 3 r/min 3 r/min BX46C - S BX46C - FR BX46C -A (Three-Phase 2-23 AC) 3 r/min.8.6.4.2.5.1.15.2.25 2 r/min 1 r/min 3 r/min 3 r/min BX512C - S BX512C - FR BX512C -A (Three-Phase 2-23 AC) 3 r/min 1.25 1..75.5.25.1.2.3.4.5 2 r/min 1 r/min 3 r/min 3 r/min A number indicating the gear ratio is specified in the box in the product name. For the electromagnetic brake type, M is entered where the box is located within the product name. H-44
Technical Reference BX62A - S BX62A - FR BX62A -A 5. 4. 3. 2. 1. 3 r/min 2 r/min 1 r/min 3 r/min 3 r/min BX62C - S BX62C - FR BX62C -A (Single-Phase 2-23 AC) 3 r/min 3. 2 r/min 2. 1. 1 r/min 3 r/min 3 r/min BX62C - S BX62C - FR BX62C -A (Three-Phase 2-23 AC) 3 r/min 2. 2 r/min 1..5 1 r/min 3 r/min 3 r/min Selection Calculations BX64S - S BX64S - FR BX64S -A 3..2.4.6.8 3 r/min.2.4.6.8.2.4.6.8 2. 1. 2 r/min 1 r/min 3 r/min 3 r/min Service Life Standard AC BLH Series.2.4.6.8 1. 1.2 1.4 Speed Control BLH15K- BLH15K-A 1..5.1.2.3.4.5 3 r/min 25 r/min 2 r/min 15 r/min 1 r/min 5 r/min 1 r/min BLH23K-, BLH23K- FR BLH23K-A 2. 1..5 3 r/min.2.4.6.8.1.12 25 r/min 2 r/min 15 r/min 1 r/min 5 r/min 1 r/min BLH45K-, BLH45K- FR BLH45K-A 4. 3. 2. 1. 3 r/min 25 r/min.4.8.12.16.2 2 r/min 15 r/min 1 r/min 5 r/min 1 r/min Stepping Servo Gearheads BLH51K-, BLH51K- FR BLH51K-A 6. 4. 2. 3 r/min.1.2.3.4 25 r/min 2 r/min 15 r/min 1 r/min 5 r/min 1 r/min Linear Heads A number indicating the gear ratio is specified in the box in the product name. For the electromagnetic brake type, M is entered where the box is located within the product name. CAD Data, Manuals Technical Support Please contact the nearest Oriental Motor sales office or visit our ebsite for details. H-45