Freqrol AC Spindle Controller Failure VSD

Normally when a Variable Speed Drive (VSD) comes in for repair, we need to remove each circuit board and test thoroughly to diagnose the problem. Very rarely can we see the issue without touching the VSD box itself. This blog is actually about an AC Spindle Controller which is a different item to VSD’s but has many parallel concepts and parts so worthy of discussion here.

Earlier this week, the Mitsubishi FR-SE Freqrol Spindle Controller arrived with a very obvious problem, the IGBT has catastrophically blown up. As you can see from the photographs, when it arrived we immediately noticed the carbon blast pathway from the IGBT. Generally speaking, Spindle Controllers are technically more complicated than your average garden variety VSD due to the nature of what it does so you would expect much more care in their design, and therefore this type of failure quite rare but it does happen all too frequently. It must have made a rather loud KABOOM sound when it failed.

From our experience of repairing many other Spindle Drives and VSDs over many makes and models, we already know the associated IGBT firing circuit would have sustained significant damage as well as much of the power circuitry. As this Spindle Drive was in an electrical enclosure, many would suspect a massive shorting issue which is a reasonable assumption. From our vast experience of repairing these type of drivers, and knowing the motors, etc are still intact and working, we think it is more likely the older discrete components like capacitors and resistors may have caused this issue, or simply a sleeping manufacturing fault that has finally popped in to say hello.

As the Spindle drive is many years old, the replacement controller boards if still available would be very expensive and in most cases, need to be imported from overseas. Our approach is to replace the damaged components on the circuit boards, and then to replace every capacitor in the box as we know these are the components that cause many failures. When we have completed the repairs our ISO9001 testing regime will ensure this Spindle Drive will have a clean bill of health.

We will shortly be returning the Spindle Drive back to the owner in better than new condition at a fraction of the cost of replacement parts alone. The only alternative the owner had was to replace the Spindle Drive with a newer model but as the newer models are configured differently, the electrical and physical modifications in the cabinet would have even more costly and have associated unnecessary risks. That is why we were asked to repair it.


Mitsubishi FR-SE Variable Speed Driver Controller