In the design of the DC motor drive circuit, the following points are mainly considered: 1. Function: Does the motor rotate unidirectionally or bidirectionally? Does it need speed regulation? For unidirectional motor drive, just use a high-power triode or field effect transistor Or the relay can directly drive the motor. When the motor needs to rotate in both directions, an H-bridge circuit composed of 4 power elements or a double-pole double-throw relay can be used. If you don't need speed regulation, you just need to use a relay; but if you need speed regulation, you can use switching elements such as triodes and field effect transistors to achieve PWM (pulse width modulation) speed regulation. 2. Performance: For the motor drive circuit of PWM speed regulation, the main performance indicators are as follows. 1) The output current and voltage range, which determine how much power the circuit can drive. 2) Efficiency, high efficiency not only means saving power, but also reducing the heating of the drive circuit. To improve the efficiency of the circuit, we can start from ensuring the switching state of the power devices and preventing common-state conduction (a problem that may occur in H-bridge or push-pull circuits, that is, two power devices are turned on at the same time to short-circuit the power supply). 3) Influence on the control input. The power circuit should have good signal isolation for its input terminal to prevent high voltage and large current from entering the main control circuit, which can be isolated by high input impedance or optocoupler. 4) Impact on power supply. Common-state conduction can cause the instantaneous drop of the power supply voltage to cause high-frequency power supply pollution; large currents may cause the ground potential to float. 5) Reliability. The motor drive circuit should be done as much as possible, no matter what kind of control signal or passive load is added, the circuit is safe.

With the wide application of machinery now, the importance of DC geared motors can not be ignored. It is an indispensable device for providing power in machinery. DC geared motors have a wide range of applications. When using DC geared motors, the voltage is not high. The phenomenon of stability is a problem we often encounter, which affects our normal use. This requires us to master the skills of dealing with the unstable voltage of the DC gear motor. Let's learn about it together. 1. Magnetic field adjustment in the excitation circuit: A suitable resistive load such as an incandescent bulb is connected in parallel across the DC gear motor resistance, and the resistance value of the resistive load after heating becomes nonlinear resistance characteristics, so that the field resistance line and the excitation The initial section of the characteristic has a large intersection angle, and an obvious intersection point with the no-load characteristic curve is obtained, so that the DC gear motor will also have a stable working point at a lower voltage; 2. Magnetic pole gasket: in the DC gear motor Benign magnetic conductive material is placed under the pole piece to reduce the excitation magnetic field gap, so that it can saturate the output characteristics when the excitation current is small, so that its output voltage can be stabilized; 3. The generator automatic excitation adjustment device is used : The generator automatic excitation adjustment device has good excitation characteristics, and has various adjustment methods such as constant reactive power and constant power factor. It is very effective to improve the stability and transient response capability of the system. The problem of generator reactive power swing caused by stability and system voltage fluctuation.

　The AC current is induced in the armature winding of the DC geared motor. Through the mechanical action of the point brush and the commutator, the current flowing into the external circuit is a DC current. The so-called commutation is to use the mechanical aspect to force the current in a coil to change from one value to another value within the pole-off time. For DC geared motors, the currents before and after commutation are equal in magnitude and opposite in direction. The commutation fault of the DC motor mainly refers to the commutation spark under the brush exceeding the standard. The surface of the commutator segment in normal operation should be smooth and clean, and there should be a layer of dark brown cuprous oxide protective layer, which can increase the contact resistance between the brush and the commutator segment and reduce the short-circuit current under the brush. The commutator is protected from wear, so that the working conditions of the commutator can be improved and sparks can be reduced.

Reasons for oil leakage of the geared motor 1) The pressure in the gearbox is too high: In a closed gearbox, friction occurs when the gears mesh to generate heat. As the working time increases, the pressure in the reduction box increases, and the lubricant splashed into the inner wall of the reduction box will seep out in the sealing area, resulting in oil leakage. 2) The structural design of the geared motor is unreasonable: if the designed geared motor does not have a ventilation hood, the geared motor cannot achieve pressure balance, resulting in an increase in the pressure in the box. 3) Oil leakage at the joint of the oil filling hole cover and the reducer housing: excessive lubrication of the gear box, damage or aging of the felt pad and rubber ring, failure of the seal, blockage of the oil return groove, failure of the oil seal, deformation of the oil filling hole cover, and blockage of the reducer motor. The pressure in the reducer is too high and the oil is leaking. 4) The maintenance of the gear box is not in place: if the gear motor cover is operated at will, even if the gear motor structure is carefully designed by the manufacturer, oil leakage will occur. Prevention and elimination methods: 1) The sealing ring cover is easy to disassemble and the structure is open. 2) Aging treatment on the reducer housing to avoid oil leakage along the closed surface. 3) The annular oil groove is cast or machined on the closing surface of the reducer base, and multiple oil return holes are connected with the annular oil groove. 4) The oil level in the fuel tank should be one-third to two-thirds of the oil level inspection hole. 5) When the oil seal is invalid, replace the oil seal in time. After operating for a period of time, the oil seal should be replaced, removed and cleaned, and the breathing valve should be cleaned. The gasket is installed on the sight glass cover and the oil drain hole, and the bolts are tightened.