The main circuit of the reversible PWM converter has many structural forms, and the H-type PWM converter is the most commonly used in the DC pulse width speed regulation system. It consists of 4 three-pole power transistors VT, VT2, VT. and VT, and 4 A freewheeling = a bridge circuit composed of pole tubes VD, VD2, VD3 and VD (as shown in Figure 1). Connect the power supply Us on one diagonal of the bridge circuit, and connect the armature of the DC motor M on the other diagonal, and U, Ub2,! B8 and U are the base drive voltages of 4 transistors, respectively. Due to the different polarity and magnitude of the base drive voltage, three types of control methods are classified in the H-type converter, which are bipolar control, unipolar control, and restricted unipolar control. Under different control modes, the voltage and current of the speed control system are different, so that the operating characteristics of the motor and the speed control performance of the speed control system are also different. In the DC speed control system, the current has the greatest impact on the motor's operating characteristics. The magnitude, direction, and continuity of the current directly affect the operating performance of the motor, so the current in the reversible PW M converter should be analyzed to grasp the operating characteristics of the motor, so that appropriate control methods can be used to ensure the speed control performance of the speed control system .
The reversible PWM converter uses the width of the positive and negative pulses of the drive voltage to control the forward and reverse rotation of the motor. When the positive pulse is wider, ton>T/2, the average output voltage is positive, and the motor rotates forward, otherwise, it reverses; if the positive and negative pulses are equal, ton=T/2, and the average output voltage is zero. In the motor stop thyristor-motor system, the measures that can be taken to suppress current pulsation are: increase the number of rectifier circuit phases, adopt multiple technology, set up smoothing reactors, 2. The position follow-up system generally consists of five parts, these five The parts are: position sensor, voltage comparison amplifier. Power electronic converters, servo motors, reducers and loads.
characteristicIts circuit is shown in circle 1, and the four three-board transistor substrates are in the American system: U,=Us, U=U=-U, as shown in circle 2(a). In the case that the transistor does not withstand the reverse pressure, VT, VT, and VT, VT, and VT, and VT at the same time, and VT, and VT, and VT, and VT, West group transistors alternately seek on and off. The load of moxibustion in Tunjiji is heavier, and the average load of moxibustion is larger. In Oãt
Ub2 and Up are positive, but because the armature inductance releases the energy storage, the current continues to flow through the armature from A to B, that is, the current id flows through the diode VD, and VD, and then flows from the loop 2 (Figure 1). The positive voltage drop generated by the current on VD and VD3 makes VT, and the ce pole of VT bear back pressure and cannot be turned on. At this time, Up=-U, so in one cycle, the converter output voltage UR has positive and negative The polarity change is "bipolar" (the armature current is shown as ig in Figure 2(b)). When the motor load is light, when t≤t
Where Ï=2-°p -1 is the duty cycle of the bipolar PWM00 voltage, and its range is -1≤Ï≤1.
It can be seen that the speed can be adjusted by changing Ï, Ï is the positive value of the motor forward rotation, p is the negative value of the motor reverse rotation, and Ï=0 the motor stops running.
Related links briefly describe the role of pwm converters based on IR2110 H-bridge reversible PWM drive circuit application
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