Pike DC governor PWM chopping technology
DC speed regulation is generally achieved by using thyristor to control the conduction angle. This paper introduces PWM chopping technology, which is suitable for high precision DC. Servo control system, Shanghai Kuanying Automation Equipment Co., Ltd. professional maintenance and design DC servo control system.
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PWM, commonly used in small and medium power systems. It uses pulse width modulation technology, and its working principle is: pass change \" turn on pulse \" width, so that The \"duty cycle\" change of the voltage on the armature of the DC motor changes the uniform value of the armature voltage and controls the speed of the motor. The PWM speed control system has the following characteristics:
1. The main circuit is simple, the power used is less, and the operating element is in the switching state, so the conduction of the circuit is small, and the installation efficiency is relatively high;
2. The switching frequency is high, which avoids the common vibration of the machine tool and works smoothly;
3. When using a low inertia motor with a small power rate, it has a high positioning speed and accuracy; Good low-speed performance, high speed accuracy, wide speed range;
5. System Frequency bandwidth, dynamic response should be good, anti-jamming can be strong. Common PWM drive system The main circuit (power rate amplifier) is constructed with H-type and T-type. See below for bipolar H-type PWM. The working principle of the driven circuit.
In Figure 1-2-2-1, VD1, VD2, VD3, and VD4 are freewheeling diodes for maintaining VT1, VT2, VT3, and VT4 three poles
Tube, Ub1=Ub4=-Ub2=-Ub3 in the figure. When Ub1=Ub4 is positive, VT1 and VT4 are turned on , VT2 and VT3 are cut off, UAB voltage=US; when Ub2=Ub3 is Timing, VT1 and VT4 are cut off, but VT2 and VT3 cannot be turned on immediately. Due to the back electromotive force of the motor, there is a freewheeling of AB. The freewheeling flows through VD3 and VD2, and the four triodes are maintained. If the freewheeling is not obtained in this process. A large attenuation, while the Ub1=Ub4 positive phase has come, then VT2 and VT3 has no conduction time; if the freewheeling process is very large, then VT2 and VT3 conduction , UAB voltage =-US. Obviously, Ub1=Ub4 is positive when the time is the same as Ub2=Ub3 is positive, UAB uniform value = 0, motor dynamic still; Ub1=Ub4 The positive time is longer than Ub2=Ub3 is When the positive time, the UAB's uniform value >0, the motor is rotating UAB motor reverse, the smaller the UAB value, the higher the speed. It can be seen that by controlling the pulse widths of Ub1, Ub4, Ub2, Ub3, the steering and speed of the motor can be controlled, and dynamic stationary can be achieved, which is beneficial to the elimination of the positive and negative dead zones.
The design of the PWM is completed. If there are any shortcomings, please give us a lot of advice. Any questions are welcome to inquire.
