Frequency converter failure analysis

- Nov 23, 2017 -

Frequency converter is an electronic power supply unit, but also to provide the frequency and voltage at the same time changes in the device, there are three kinds of circuit configuration, namely the rectifier circuit, control circuit and inverter circuit. Rectifier circuit module which is the main role is to rectify AC into DC, and inverter circuit is the role of the main switch on the frequency converter control. Control circuit is responsible for the control of the entire circuit. In order to ensure the smooth operation of all aspects of the circuit, it is necessary to strengthen the overhaul and maintenance of the frequency converter to deal with the fault of the frequency converter so as to ensure the stability of the operation.

1. Main circuit breaker failure analysis

Cause the main circuit breaker failure occurs mainly due to three points, first of all the poor cable or even the auxiliary circuit breaker auxiliary contacts, followed by the working position of the circuit breaker does not meet the actual requirements, the last point is the relevant module damage. In troubleshooting the site, inspectors ruled out the circuit breaker is not in the working position of the phenomenon, but also ruled out the possibility of cable damage by external forces, the focus of the inspection on the circuit breaker auxiliary contacts. After careful inspection, it was found that the circuit breaker stroke switch fixed position loosening, leading to poor contacts of the travel switch, through the trip switch fault code to eliminate, so that the system back to normal operation.

2. DC bus pre-charge failure analysis

Cause DC bus pre-charge the main reason for failure there are 3 points, first of all, the frequency converter pre-charge device contactor

And the circuit breaker, followed by the voltage of the auxiliary power supply of the pre-charging device is too low, the last point is the voltage sensing fault and circuit pre-charge device fuse failure. Since the DC bus pre-charging device is mainly used for DC bus

Capacitor charging, the operation of this device is before the drive starts, therefore, the cause of the failure is mostly pre-charged device extruder failure or circuit breaker failure caused by, but through the inspection of the site fault found that this There is no failure, the main reason is due to auxiliary power supply. Auxiliary power supply due to poor contact, resulting in the occurrence of the lack of phase, by changing the switch can make a variety of faults are reasonably resolved.

3. Safety circuit failure analysis

The main reason for the failure of the safety circuit is 4 points. The first point is that the emergency stop button on the control cabinet door is pressed. The second point is that the circuit breaker has been closed or the cable is not in good contact or broken. The third point, Detection of the door switch at the microswitch poor contact, the fourth point is the emergence of the input module and terminal module failure. Most of these faults occur after the frequency converter is stopped normally and restarted. The relevant inspectors conducted a preliminary analysis of the fault and predicted the cause of the fault mainly due to human factors. By checking the control cabinet of the frequency converter, it is found that the economic button of the frequency converter is manually pressed after being stopped, and it is not found during starting, resulting in the situation that the frequency converter can not be started.

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