DC injection brake

[Guineafowl]

Fitted to a big Wilson table saw, 3ph, recently bought cheap.

Running on a rotary phase converter, which runs a Crompton S10 brake just fine.

When I connect power, the brake contactor K5 pulls in, and stays in. The DOL contactor K1 for the motor is disabled. This isn’t right.

Diagram:

I’ve made sure the wiring is as above, but CB1 in the unit is only single pole to the L1 terminal of the brake unit, and is a normal MCB. The diagram seems to show a normally open type of breaker. What is it?





Relevant control stuff:
According to this, braking is triggered by voltage between inputs L1 and 4, but this is the initial state of the unit, with power applied.

Link to manual:

https://www.inverter.co.uk/applications/manuals&datasheets/dc-injection-motor-brake-instructions.pdf

 

[Guineafowl]

An older version shows two brake fuses, which is more like my setup, except there’s only one, and it’s an MCB:

 

[m_c]

K5 should disconnect once the DC brake times out, which should then allow the saw to be started.

 

[Guineafowl]

K5 should disconnect once the DC brake times out, which should then allow the saw to be started.

K5 is on as soon as the upstream isolator is switched on, and stays on, no timeout. But if you take this description...:

"5.1.3. Control Input. L1, 4
The control input is the primary of a 2VA transformer. Braking action is triggered by sudden application of voltage on terminal 4."

... And look at the top diagram, power is immediately applied between L1 and 4, which is what triggers the unit. Doesn't make sense, unless it's just faulty and failing to time out?

 

[Brad93]

Have you checked you've got the right dc voltage

 

[m_c]

That sounds correct, in that when first switched on, the braking action is triggered.
However going by what I understand form the manual, it should time out.

Have you tried adjusting the timer pot?

 

[Guineafowl]

Yes, tried the timer pot.

Here’s the diagram on the brake unit itself. I don’t think it matches the wiring diagram above. Pin 4 is normally unconnected here, for a start.

Any idea what K is here, which appears top and bottom? I assume braking contactor?

Is the enable switch part of K?

 

[m_c]

Is there any DC output when the power is applied?

A thought I just had, is the braking unit being powered by the generated phase?
The generate phase is likely to have some timing/voltage inconsistencies, and I'm wondering if that is somehow causing the relay not to react how it should.

 

[Guineafowl]

Is there any DC output when the power is applied?

A thought I just had, is the braking unit being powered by the generated phase?
The generate phase is likely to have some timing/voltage inconsistencies, and I'm wondering if that is somehow causing the relay not to react how it should.

I was thinking along the same lines. The braking unit also has an earth connection, despite being a plastic box, so I assume some kind of reference, but the phase-earth voltages are all different and not 240V.

I’ve been over the brake unit PCB and everything tests out just fine. Cleaned all the contactor contacts.

No manual for the converter - 10hp Boost Energy unit, and they’ve now gone bust. I think the generated phase is L3 so it might be worth swapping everything to L1 and L2.

I might offer it for sale, or exchange with a normal DOL, since I’m pretty sure it’ll work just fine on normal power, and I don’t need it. Just a big old 3hp sawbench I’ll use for big ripping jobs and freehand crosscutting firewood.

Any interest on here, do you think?

 

[Guineafowl]

Forgot to say, no DC output, but I might have just been missing it.

 

[m_c]

In a commercial setting, the brake is a legal requirement, however in a private setting, you can do whatever you like.

The lack of DC output is suspicious.
Was the saw working correctly before you bought it?
It could just be that the module is faulty.

 

[Guineafowl]

In a commercial setting, the brake is a legal requirement, however in a private setting, you can do whatever you like.

The lack of DC output is suspicious.
Was the saw working correctly before you bought it?
It could just be that the module is faulty.

Not sure - bought remotely for £70, along with a nice Wadkin planer, so I didn’t ask too many questions.

The motor is an absolute beast - never seen such a large 3hp one. I’ve often wondered if modern motors are so much smaller because of improved design or just skimping.