Any electrical engineers here?

[Macsky]

I’ve got a problem with a small hydro generator that I look after. The brake was was recently for refurbishment. It is an electromagnetic set up, sits on the end of the motor, fixed disc on the back of the motor, then brake pad on motor shaft, then brake mechanism on the end, spring applied, energise to release.
It has failed and eaten right through the available wear on the pad, now freewheeling.

The brake supply is 240v from the control unit, through a rectifier to the brake. The rectifier and the coil within the brake unit appear to be goosed. Is there any way to tell which went first? Company are saying rectifier blew first, causing damage to brake coil........under which circumstance the brake would obviously not be covered by any warranty from the refurb work. Will this be right? Is there any way of knowing?

 

[TechWise]

Very very difficult to work backwards and figure out what went first. Is the rectifier a complicated looking thing under computer control or is it just a basic diode bridge and a whopping great capacitor?

 

[blackisleboy]

Agree with above - really difficult to work backwards.
If you need help then I'd suggest Proterra Energy at Drumnadrochit. One of the owners is an electrical engineer, and another a mech, so likely they will be able to sort you out.

 

[Macsky]

Very very difficult to work backwards and figure out what went first. Is the rectifier a complicated looking thing under computer control or is it just a basic diode bridge and a whopping great capacitor?

Basic I’d say

 

[Macsky]

Agree with above - really difficult to work backwards.
If you need help then I'd suggest Proterra Energy at Drumnadrochit. One of the owners is an electrical engineer, and another a mech, so likely they will be able to sort you out.

Thanks for that, it’s spanns Babcock that installed the system, it’s been a lot of bother and their service costs are eye watering!

 

[TechWise]

This looks like the rectifier unit here. You may be able to buy direct.

Electronic modules & rectifiers - Universal Collection | Kendrion

Single-phase rectifier from Kendrion ✓ Universal & versatile ✓ for drives with high cycle rates ✓ ➢ learn more

www.kendrion.com

On the face of it, it looks like a simple diode rectifier so not much that can go wrong. It looks as though it's just a rectifier and a switch. It says it's an "overexcitation rectifier" though. I'm not quite sure what that means or if something is maybe being lost in translation. My guess would be that it just means it can withstand a short overload when the brakes are initially applied or released. However, it would suggest that there might be something clever going on in there that would prevent it from being replaced with a more readily available part.

A coil is generally just a coil - not much to go wrong and generally able to survive a short overcurrent so long as it's turned off before it melts which usually takes at least a second or two. Is there no circuit breaker protecting the system?

 

[Macsky]

This looks like the rectifier unit here. You may be able to buy direct.

Electronic modules & rectifiers - Universal Collection | Kendrion

Single-phase rectifier from Kendrion ✓ Universal & versatile ✓ for drives with high cycle rates ✓ ➢ learn more

www.kendrion.com

On the face of it, it looks like a simple diode rectifier so not much that can go wrong. It looks as though it's just a rectifier and a switch. It says it's an "overexcitation rectifier" though. I'm not quite sure what that means or if something is maybe being lost in translation. My guess would be that it just means it can withstand a short overload when the brakes are initially applied or released. However, it would suggest that there might be something clever going on in there that would prevent it from being replaced with a more readily available part.

A coil is generally just a coil - not much to go wrong and generally able to survive a short overcurrent so long as it's turned off before it melts which usually takes at least a second or two. Is there no circuit breaker protecting the system?

There is a circuit breaker, it had tripped.

Would a goosed coil be capable of damaging the rectifier? Would a goosed rectifier goose the coil? Which is more likely?

 

[TechWise]

There is a circuit breaker, it had tripped.

Would a goosed coil be capable of damaging the rectifier? Would a goosed rectifier goose the coil? Which is more likely?

It's really difficult to say which is more likely. On one hand, coil fails, huge current flows into broken coil through the rectifier and destroys the rectifier. No way of knowing how much of an overcurrent pulse the rectifier can withstand. On the other hand, rectifier fails, AC voltage makes it through to the coil then maybe damages the coil? I would have expected the coil to survive an AC voltage just long enough for the protection to trip first but that's just my opinion based on what little we know.

I'm afraid it really is virtually impossible to work back from charred remains. It would be virtually impossible to prove it either way on the balance of probabilities so I doubt you'll get anywhere arguing the point.

 

[Macsky]

It's really difficult to say which is more likely. On one hand, coil fails, huge current flows into broken coil through the rectifier and destroys the rectifier. No way of knowing how much of an overcurrent pulse the rectifier can withstand. On the other hand, rectifier fails, AC voltage makes it through to the coil then maybe damages the coil? I would have expected the coil to survive an AC voltage just long enough for the protection to trip first but that's just my opinion based on what little we know.

I'm afraid it really is virtually impossible to work back from charred remains. It would be virtually impossible to prove it either way on the balance of probabilities so I doubt you'll get anywhere arguing the point.

Thanks that’s good to know. At least we can go down swinging