Allen Bradley frequency inverter (11.5 kW) repair

The images clearly show the state that the device was in prior to the repair. It showed “no signs of life”. 

The extent to which the device was damaged was visible only when we performed the initial cleaning of dust and burnt out parts. In addition to various parts being burnt out (input filters, input full wave rectifier and IGBT module), and the visible burning out of the printed conductive tracks at the input part due to the intensity of the voltage, an interesting malfunction was found later on.

Namely, in addition to the IGBT module being burnt out, the chip in charge of the control of the output power on U, V, W connections for the external motor was also burnt out – a fact which could not have been established merely by using a universal measuring instrument, but rather owing to the years of professional experience. 

Although the inverter was showing to be in order with respect to Ohms, actually by lightly going over its casing with a finger, one could notice that it had a tiny, barely visible crack on it due to the burn out. Only a microscopic examination revealed the actual damage and the chip could clearly be said to be unusable.



This video shows the first testing of the frequency inverter after the repair. One can see the unhampered rotation of the motor and the possibility of controlling the number of the device’s revolutions.

After this first testing, the device had to undergo another testing on the test scale. As it had been very damaged, this was necessary in order to see if the device itself could still be used for industrial purposes, or only for some auxiliary testing purposes. Hence the device was placed under 24 hour load, to be monitored for current changes and the like.