Inverter problem

Hello all, need to pick your brains.

I have just acquired a 3 phase motor, inverter and newton tesla control pendant.

The motor is an old Crompton Parkinson motor, the inverter is a Mitsubishi.

Problem I have is the motor does not seem to have any power, so much so you can stop the pully that’s attached by hand,

I am no expert with this so am going to pass to an electrician to look but just thought before I do it might be worth asking.

Thanks all.

Are you sure that the motor is not configured for 415 volts (Star.) rather than 240 volts (Delta.) ? Have you configured the inverter for the correct maximum motor current ?

Les.

Hello Les, i don't know sorry, i have taken a photo of the connections but they mean nothing to me, unfortunately i don't even know if it all worked before it was passed to me.

It looks possible that the motor is star connected, it looks vaguely like there are multiple connections to the "N" terminal. It needs rewiring in delta to run off a conventional VFD as Les suggests.

It looks like it is configured for star connection (415 volts.) Are there three wires from inside the motor connected to the "N" terminal or just one. If there are three wires it should be possible to configure it to delta (240 volts.)

Les.

Thanks both, will take it in somewhere and have it checked.

If there are 3 wires going to the neutral point, you’re in luck, otherwise you will need to dismantle the motor and dig out the star point.

There are 3 seperate windings in the motor, so if you do have six wires emerging already, its fairly easy to work out which pairs go together using continuity on a multimeter or a battery and bulb.

Once you have the ends of the three seperate windings identified, join them as pairs i.e keep each winding seperate and connect the three phases from your inverter to the three pairs.

There could be a wiring diagram on the inside of the terminal block cover that may tell you the connections for Delta., And the plate on the side of the motor should indicate that it can be used on 415 or 240 Volt. 3 phase.

Looks like there was a sticker on the back of the plate but its missing, this is a photo of the main plate,

Cannot tell from the photo how many wires go to the N, looks like 2, but will check tomorrow.

According to the plate its a star /delta dual voltage motor, so should definitely have at least 6 wires emerging.

Data plate gives voltage and current for both star and delta connections so there will be wires that can be got at and shifted around on the back side of the terminal plate. Not much room to work in there. The backside of the plate was wired up first before fitting it to the end bell and finally assembling the motor.

If its anything like the Brook Gryphon equivalents working out which wire is which isn't easy without a meter and some experience. Probably quite easy to get a motor coil reversed. Unlike a modern 6 terminal motor this breed were not made to be changed over in the field. Star - Delta choice was intended as a factory option.

If you have access to someone who knows about these motors its probably best to get the professionals in. Especially as the current non-working condition indicates that its been through the hands of one-who-didn't-know.

Clive.

Thanks all.

Totally agree Clive,

i have just checked and there are 3 wires going to N..

so..

A = Red

B = Yellow

C = Blue

N = White / Brown / black

Looks like this has answered my qustion..if mesh is the same as delta.

Yup mesh is what you need

Be great if the internal wires are colour coded. Even if the colours are different you should be able to work up a conversion chart. If they aren't colour coded apply your own and be very careful to identify the individual windings.

I know a guy who didn't colour code his wires. Said "Yeah, yeah this is easy" and had a major panic attack halfway through on "sort of" loosing track of what muggins was doing!

As is so often the case it isn't really that difficult but neophytes need to take a bit more care and bit more time. Taking twice as long to get it right first time is always quicker than sorting it it out after doing it fast but wrong.

Clive.

I have no idea who Raynerd are but what a badly drawn diagram they have produced!

The presence of the 'N' neutral terminal in the lower diagram could easily confuse someone unknowingly as it could be construed as connected to the black wire.

Ian P

Chris Raynerd is a hobbyist/engineer. I don’t think a photocopy pic of a motor winding diagram from a motor has much to do with him. Standard drawing, as far as I see it. If connected to both, it would have shown a link? Modern day drawings would be better (a definite dot at each actual connection), but this is not modern.

I know Chris too. this is not his drawing, just a copy from a motor label he had....

Hello all.

This is a picture i found on the internet, i thought is was extremely useful.

If I have accidentally wandered into a copyright issue then if the moderators could just please delete.

Anyhow, my thanks to Chris as it was extremely useful.

Thanks.

I apologise to Chris Raynerd. I thought the watermark was because it was a company image and it was the originator of the image I was being critical of, rather than any individual.

The image looks like a photograph of a label on a motor and I think could have been drawn more clearly to eliminate anyone misunderstanding it.

Ian P