Seig SX3

There I was just drilling and tapping some M5 threads, when I pressed the start button and the whole workshop plunged into darkness, the earth leakage trip had tripped, so I reset it, pressed the start button on the Seig again and voila, earth leakage trip went again.

I have had the front operation panel off and checked the wiring for obvious loose wires, nothing there. Unbolted the base from the floor and dragged the m/c out so I could remove the rear covers, again no loose wires, after checking all wires, connections and scrutinizing the circuit boards for any obvious blown components, I unplugged the motor power and control wires and finally the electrics stayed on, then I reconnected the control wires, turned the power on and it still stayed on, but when connecting the motor power wires, the trip goes. So I am thinking there is an issue with the motor. Does anybody have any experience of this, it is the 1000w brushless device, there is resistance between the wires which changes when rotating the motor shaft. Connecting my meter between the motor body and each wire does not show any circuit. Any help would be appreciated.

Angus

You need to test between the windings of the motor, and the motor chassis with a megger type high voltage tester. I think other than that you have done all the right things, and eliminated all other causes........it looks like the motor has an earth fault, which means the insulation is breaking down and leaking current to earth, only other things to check are starting capacitor, and centrifugal switch if it has them. Take the terminal box cover off the motor and see if there is a strong smell of burnt varnish!

Good luck,

Phil

The motor is a multi phase motor with Hall effect devices for commutation.......hence the control wiring back to the main board.....

As Phil says, a megger check of the windings to the shaft of the motor will prove effective....

Some inverters cause nuisance trips, due to high-frequency signals 'leaking' enough current into the earth to trip an ELCB. The control circuitry for BLDC motors is very similar to an inverter and I wouldn't be surprised if the same effect can occur.

In the case of an inverter this is not a fault, nor is it a risk, and it is an accepted solution to use a higher current ELCB than the usual 30mA type.

Neil

Many thanks for the prompt responses.

So now I am looking on ebay for a megger, should I test at 250V, 500V or 1000V? I know the mains is at 240V but should there be a safety factor of 1.5x / 2x? I have never used a megger before hence the stupid question.

Angus

I have recently bought an insulation tester via ebay look up VC60B it was listed at 29.99 or make me an offer so I replied £25 and it was accepted. The tester arrived this morning from London area I believe, not PRC. The meter is much better than I thought it would for the price, comes with leads etc. The meter has 3 ranges 240, 500, and 1000 volts digital read out and with measure volts AC and DC. John

Do you have power feed on the X-axis ?

I used to have an SX3, fitted with a Seig power feed and lubrication oil from the table got into the limit switch at the front, shorted out the contacts and tripped the circuit breaker.

Paul.

Just to update everyone who has replied to my plight.

A megger arrived yesterday from China, no instructions, but a quick web search gave me the information I needed to be able to test the motor wires. I had a resistance of 13R on the red wire and nothing on the blue and brown, testing at 250v. 13.3R on the red and nothing on the blue and brown, testing at 500v. 798R on the red, 1653R on the blue and 718R on the brown , testing at 1000v, the reading at 1000v were jumping around a bit.

On the assumption that the motor is shot, I removed it off the m/c and opened it up, every third coil of the windings is black while the other two windings are copper coloured. Also the plastic shroud that covers the motor end cap where the hall effect switches are, was showing heat distorsion.

There has never been a smell of burnt varnish,but I think the motor has been cooked at some time in the past. All the ventilation holes are clear and the work I have done on the m/c has been light duty, as it soon lets you know if it is being overloaded as it vibrates the head.

Have I missed anything before I order a new motor?

Many thanks for all the replies.

Angus

.

Yes. ............. Possibly.

Check that the motor when it departed this world did not also drag off the control board to meet the grim reaper.

Nick

I ordered a new motor from Arc Euro Trade and it arrived yesterday, did a quick meggar test of the three wire, all okay as expected. The shaft turns with a lot less force than my knackered motor, even though nothing touches it!

As I had already inspected the drive board, I fitted the new motor and powered up, the lights stayed on and the motor span, yippee

All I had to do now was to realign the base with the holes in the concrete floor, bolt it down so the bed is level and carry on tapping the M5 holes on the job that is sat in the dividing head.

When the Seig is running, it is a lot quieter now than it was with the old motor

Does anyone know if I can get the old motor rewound as it would be nice to have a spare as new ones are £340

Thanks everyone for your responses

All the best

Angus