Wiring an inverter

In case the same scenario befalls anyone else....

i have a Compact 5 which is a nice machine but suffers from a tediously unfriendly and slow speed change mechanism using the original motor. When I was offered a second hand Telematique Altivar 11 inverter cheaply albeit with a 'no proof of functionality' label, I took it since it would avoid all (most) belt changes.

I then bought a brand new 3 phase motor from Germany through eBay with a similar rating to the old one in the same frame size which arrived Wednesday.

A couple of hours wiring including the remote speed and forward/reverse switches and setting the motor connections from Star to Delta and I was ready to run.

Power up resulted in a nasty noise reminiscent of a slipping stepper motor and some motor vibration but no inclination to run at all. Several hours checking the parameters on the inverter as well as all the wiring left me thinking that it 'should' be ok, especially since it was not reporting any error condition.

Turning to the motor, I disconnected it and checked the 3 windings, which showed 2 x open circuit and one at 20 ohms. Not really believing that I had blown 2 windings in the space of a couple of hours, nor that it was supplied faulty, I returned it to the original Star connections. Result, 3 windings with 20 ohms each...

a very much closer look at the windings revealed that they had been incorrectly wired such that the normal Delta strap connections had simply shorted out 2 windings, leaving a single winding to rotate the motor...In Star mode, the problem was masked thanks to the common connection.

The moral of the story? Don't assume that the fault lies in the unproven, second hand item, do check the brand new components as well...

Hi Simon,

sorry to hear about your trouble, I hope you got a refund or a replacement motor. Good advice to check everything when something doesn't work.
 I am currently working on a similar conversion from single-phase motor to 3-phase motor and inverter, a test connection has been made and everything worked as expected.

Thor

Edited By Thor on 16/08/2013 19:14:44

Unfortunately it is more comman than you may think and a good sparky will test the motor before installing it .

Check and identify the terminals for the windings with a Multimeter then run a Mega on it to check the insulation of the windings .
If all is well install it , if not send it back .

Not sure of how you will go with warranty as may manufacturers state that thier equipement must be installed by Qualified persons - a sparky etc .

Ian.

Ian,

Normally the instructions for the terminal links are in the cover of the terminal box. If the motor doesn't work when connected in accordance with these, then surely it doesn't matter who tested it?

I know we are in a mad world where everything must be done by a "Qualified Person", unfortunately some of these are not as qualified as one would hope. I could tell you tales of gas fittings/fitters that would make your hair curl!

Phil

Thanks for your comments. Actually it was an easy fix since each winding terminated in the connection box on the motor with a screw terminal. Undo the two incorrectly wired windings and swap. Put everything back together and away it went.

The key was when I looked at the wire colours and realised that the Delta strap links were linking identical colour wires together, and my meter confirmed that the link was forming a straight short.

If i was going to pursue the warranty route, I was going to have to negotiate through an item bought on a UK PayPal account from eBay Germany delivered to France, which was manufactured in Bulgaria, all discussions up to that point having taken place using Google Translate since my German barely runs to much more than ordering a beer....happy to have fixed it without recource to all of that!

simon

Have just had the table motor on my Centec 2B rewired to delta and fitted an inverter and all seams well, when it comes to things like motors and inverters I buy from a local company then if there is a problem it goes straight back to them no buggering about posting and waiting for reply's and them saying you have caused the problem.

Al.

Phil,

In most cases i would agree with you regarding the wiring diagram but i have seen motors that had nothing inside the cover and have also seen the same issue that Simon has quite a few times .
I believe that a few minutes spent checking the motor over is time well spent .
I know that many will not have access to a Megaohm Meter but even a cheap multimeter will check continuity and allow one to determine that the windings are wired as per the diagram if it has one .

Here in Australia in some states (maybe all by now ) it is against the law to change the washers in your taps unless you are a licenced Plumber ! Although you can buy them just about everywhere !
The Nanny Country gone mad !

Ian .

Phil, you were saying about gas fitters, when Whispertech started installing the Whispergen hot air engine power supplies in UK they found that they had to set up a training school to teach the licenced gas fitters how to connect the gas! Ian S C

I recently bought a new domestic gas oven, running on bottle gas, they would not deliver it without a certified gas fitter on site. This is for an appliance with a standard bayonet fitting, I told them I was qualified, so that was all right. Also had to fit a chain to the top to stop the thing falling over! Sorry for off topic.