DC Brake Repair / Replacement

[Brad93]

This is a small radial arm at work.
It stopped working some time ago and their electrician gave them a price of £1100 to replace this brake.

I've checked the contactors and all switches, all check out okay which leaves the boards.

Short of a wiring diagram or sending back to the manufacturers, can I replace this unit (or even just the boards) with a cheap-ish alternative.

We need to keep the safety function of a long microswitch/estop that if pressed stops the machine immediately.

 

[Robotstar5]

Don't forget someone has to sign their name to any safety related changes/modifications

 

[arther dailey]

so has the brake been tested for circuit itself ? is it electrical coil/magnet system ? if so possibly work backwards from coil .

 

[awemawson]

Is it a separate brake or does the electrics inject DC into one (or more) of the AC windings having isolated them from the supply first.
I suspect the later with one relay cutting the AC supply and a fraction of a second later the other applies DC to the windings as a brake.

 

[Brad93]

Is it a separate brake or does the electrics inject DC into one (or more) of the AC windings having isolated them from the supply first.
I suspect the later with one relay cutting the AC supply and a fraction of a second later the other applies DC to the windings as a brake.

That's exactly what it does. Left hand contactor is main contactor, right hand contactor injects the DC voltage.

 

[Brad93]

so has the brake been tested for circuit itself ? is it electrical coil/magnet system ? if so possibly work backwards from coil .

No it's an injection brake as per the photos "DC INJECTION BRAKE"

 

[Brad93]

Don't forget someone has to sign their name to any safety related changes/modifications

This company doesn't do any health & safety mate - they were surprised when I asked when the filters were changed on the portable extraction unit.

Never was the answer.

 

[m_c]

RDM still exist - https://www.rdmengineering.co.uk/expertise/drivloc/ but only build to order now.

Manual for the SM variant can be found at https://www.rdmengineering.co.uk/wp-content/uploads/2019/08/Drivloc-SM-Instructions.pdf
It's probably worth going through the manual, and checking voltages/pots are correct, and it's getting voltage where it should be.

 

[arther dailey]

No it's an injection brake as per the photos "DC INJECTION BRAKE"

ok, cant see that on pics but hope you get it sorted.

 

[Agroshield]

....their electrician gave them a price...

This looks to be a similar power drop-in replacement:

https://www.cef.co.uk/catalogue/products/1781711-2-2kw-415v-direct-on-line-dc-injection-braking-unit-4-6a-overload

You could download the manual for it and see what it accepts as input from the machine and what it gives as output to the machine. Then see if that makes any sense in relation to the wires on the one you have.

 

[Brad93]

This looks to be a similar power drop-in replacement:

https://www.cef.co.uk/catalogue/products/1781711-2-2kw-415v-direct-on-line-dc-injection-braking-unit-4-6a-overload

You could download the manual for it and see what it accepts as input from the machine and what it gives as output to the machine. Then see if that makes any sense in relation to the wires on the one you have.

Bit sharp that. The lads had to fight to be allowed more than one pair of latex gloves a day!

 

[Ali]

They come up on eBay

Unused RDM Engineering Driv-Loc DC Injection Brake 4.5-7.4KW Wadkin etc | eBay

A Unused boxed RDM Engineering Driv-Loc DC Injection Brake 4.5 - 7.4 KW immaculate condition and costs over £700 new.

www.ebay.co.uk

I remember these things being a pain when we used to work in schools. RA saws are a risky bit of kit.

 

[awemawson]

That huge price is why I made my own for the three 7.5 hp motors on my Dominion combination wood worker. Previous owner had replaced it with modern light weight bent tin chinese version to comply with HSE as he used it commercially. For me it was a hobby so making my own was viable from a liability standpoint. Pair of stout contactors and custom timer modules per motor housed in an industrial enclosure worked well and so far have done for a good 8-10 years (jinx - fingers crossed!)