Teco FM-50-201 VFD Attempted Repair

[Muttley Snickers]

Greetings everyone, I recently acquired a Teco FM-50-201 N4FS variable frequency drive and after a quick inspection it looked ok until later I noticed on the underside of the cover evidence of a malfunction, I used the cover as a guide to pinpoint the damage which was semi concealed behind a rather large capacitor. I removed one of the large 330uf 400 volt capacitors to gain access after discharging both it and it's mate across a large wattage 150 ohm resistor, the capacitors had virtually no charge left in them but after recently getting whacked by a camera flash capacitor I didn't want to risk it. 

I found that a 220k ohm resistor (R310) although fully intact and operational had completely blown a leg and alongside it a 10nf (C303) polyester capacitor which looked like it also had been subject to a blast but after removal and testing it was found to be unaffected but will be replaced nonetheless as will the resistor.

The main component that gave up the ghost was a 0.01uf ceramic capacitor (C305) which had blown apart and lost one face which happened to be the face with the markings, initially I thought that it was a MOV but after further investigation and a cleanup of the board the silkscreen revealed that it was a capacitor, I tested it on the LCR meter and the readings were completely unstable so I rang the manufacturer and they were very helpful and indicated that it would have been a 0.01uf ceramic.

The original was 10mm pin pitch and around 9mm diameter and I picked up a replacement from the local electronics shop but they only had 0.01uf rated at 3kV which are much bigger at 13mm diameter but the same pin pitch, should I try and find exactly the same that was there in the first place or will this 3kV component be ok as I am not sure what the rating on the original would have been.

I have inspected and tested most of the other components on the boards and it all looks in pretty good order, I have not powered the unit it up since receiving it a week or two ago, from what I have read these units do not like having power removed whilst they are under load and the manufacturer did indicate that the damaged components may be part of the protection circuit.

Many Thanks

Muttley

[Muttley Snickers]

Just some more pictures of the internals, I have plenty more as well as manuals.

[nowlan]

International Rectifier
3-PHASE BRIDGE DRIVER
http://www.irf.com/product-info/datasheets/data/ir2133.pdf

Description
The  IR2133IR2135/IR2233IR2355 (J&S) are high voltage, high speed
power MOSFET and IGBT driver with three independent high side and
low side referenced output channels for 3-phase applications.

Features
• Floating channel designed for bootstrap operation
       Fully operational to +600V or+1200V
       Tolerant to negative transient voltage
       dV/dt immune
• Gate drive supply range from 10V/12V to 20V DC and up to 25V for transient
• Undervoltage lockout for all channels
• Over-current shut down turns off all six drivers
• Independent 3 half-bridge drivers
• Matched propagation delay for all channels
• 2.5V logic compatible
• Outputs out of phase with inputs
• All parts are also available LEAD-FREE

[Muttley Snickers]

Just some more pictures of the internals, a manual and the capacitor that I picked up but don't know if it's suitable.

[SeanB]

3kV will be fine, as the original likely was a 2kV unit.

[Muttley Snickers]

Thanks SeanB,
I wasn't too sure and as you can see from the blast foot print she must have gone off with a bang, it's all ready to be hopefully fixed and reassembled then tested on the bench but I first need to put together a protection box with breakers. an RCD and a big mushroom kill switch all of which are at hand and I've been meaning build one for ages for general testing, also I have plenty of motors in the workshop to test it on.

Many Thanks

Muttley


Here's the full manual for the unit that I have.

[SeanB]

If you have any spare VFD's you could post them to me to use.

Just repaired one at work, replacing the horrid little push switches on the control panel. they go open circuit. Must remember to order some new ones, I used ones from an old monitor as they were about the right size.

[Muttley Snickers]

I do see quite a few but never bothered with them before and need to learn a bit about them, this should be a good first unit for testing providing nothing else was affected, just hope that I haven't wasted my money...

https://www.eevblog.com/forum/chat/what-did-you-buy-today-post-your-latest-purchase!/msg740774/#msg740774