Common test methods for DC Drives maintenance

Common detection methods for DC Drives maintenance:

1) The output is the highest speed, which is not adjustable. The measured rectifier voltage of P4 is 200V.

A. To access 220V/220V isolated maintenance power supply for the device, disconnect V1 gate resistance from the circuit, that is, disconnect V1 trigger current path, and test P4 rectifier voltage is still 200V, then the thyristor V of the main circuit will be broken down and short-circuit.

B. The performance of the circuit W2 with a given speed deteriorates, and the resistance value between the movable arm and the upper fixed end becomes larger, so that the regulated voltage cannot rise and the maximum speed signal is mistakenly given.

2) FUSE FUSE is broken, check that none or two of the four diodes inside the bridge rectifier circuit P4 have been short-circuited.

At the same time, the protection circuit W1, N3, N4 circuit should be checked for failure, so that the protection failure, so that P4 burned.

3) The output voltage is zero. Involve three aspects of the circuit, a main circuit damage, such as thyristor V1, current sampling resistance R3 open circuit damage; The second is the misoperation of the protection circuit, which forces the phase shift to trigger the circuit to stop working; The third is called the phase trigger circuit itself fault, can not output the normal phase shift trigger pulse signal.

A. Check that there is no open-circuit fault in R3, short-circuit T1 and T2 poles of thyristor V1, and measure whether there is 200V voltage at the output end of P4 rectifier. If there is still no normal DC voltage output, P4 is damaged (load resistance is added to make the test easy to judge), if there is normal voltage output, continue to check the next step;

B. Use wire or tweezers to short connect the C and E emitter of the pulse amplifier V2, manually connect the trigger current path of V1, and the output voltage of P4 is still 0, indicating that the thyristor V1 is damaged; P4 can output 200V DC voltage, indicating that the main circuit is intact; Proceed to the next check;

C. Before checking the phase shift trigger circuit, it should first rule out whether the protection circuit is misoperated, so that the phase shift trigger circuit can not be put into normal work. If fault indicator D4 is always on, it indicates that the overcurrent protection circuit is in a state of misoperation. Check the N3 and N3 protection circuits. If D4 is not bright, test V6 Uce is less than 1V, then V6 breakdown damage.

A more effective inspection method, the emitter of V off the circuit board, adjust W2, measure the P4 output voltage normal changes, the fault is the protection circuit error control; Test P4 still no output, the fault is in the phase trigger circuit, continue to check the next step;

D, adjust the W2, N2 1 foot about whether there is a corresponding 0 to 8 v dc voltage output, if the change is normal, the N2 at the corresponding level and the level before the phase-shift circuit works well, failure in C5, V2 touch power amplifier stage, such as V2 magnification become low, or open circuit, capacitor C5 capacity decline or loss of capacity, causing trigger current is too small, V1 can't normal open, etc.; If the first pin of N2 has a fixed positive voltage of more than 8V or 0V, the fault is in N2 and the preceding circuit. The next step should be continued;

E. According to the circuit analysis, judge the waveform of each point, and then estimate or calculate the voltage value of the key point of the phase shift trigger circuit, make the fault diagnosis, and then complete the repair of the DC Drives.