Symptom: The device cannot be started. Only the DC current meter has an indication when starting. There is no indication for the DC voltage and the intermediate frequency voltmeter.
Fault analysis and processing are as follows:
1. The inverter trigger pulse has a missing pulse phenomenon. Check the inverter pulse with an oscilloscope (preferably on the G-K of the thyristor). If there is a missing pulse, check if the connection has poor contact or open circuit. Is there any pulse output at the front stage?
2. Inverter thyristor breakdown. Use a multimeter to measure the resistance between A and K. In the absence of cooling water, the value of A-K should be greater than 10K, and the resistance is 0. If there are two damages during the measurement, remove one of the connected copper bars and judge whether one or two are damaged. Replace the thyristor and check the cause of the thyristor damage.
3. Capacitor breakdown. Use the × IK block of the pointer multimeter to measure the capacitance of each column to the common terminal. If there is no indication that the column is broken, remove the damaged capacitor pole.
4. The load has a short circuit and grounding. The resistance of the coil to ground (without cooling water) can be measured with a 1000V megger (shake table), which should be greater than 1MΩ, otherwise the short-circuit point and grounding point should be excluded.
5. The IF signal sampling loop has an open or short circuit. Use an oscilloscope to observe the waveform of each signal sampling point, or use a multimeter to measure the resistance value of each signal sampling loop to find the open or short point. Focus on the intermediate frequency feedback transformer, whether the primary side is open (caused by the snorkeling sensation).
