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Electric Motor Configurations

AdrianWint

So I have a (new) 1.5kW motor.

The motor rating plate declares the machine as being 380V 60Hz 3 phase, 3.96A and then ' WIRED IN STAR'.

The rating plate only gives details about the star configuration - it doesn't mention delta.

Looking inside the terminal box, all 6 wire ends are brought out - three being linked to form the star point.

Removing the star point reveals that all three coils are indeed electrically separate & the opposite ends are all displaced by one position as they would need to be if one was to reconfigure this machine into delta by turning the three links through 90 deg.

My question for the learned forum - why hasn't the manufacturer given any details about the delta configuration on the plate? Indeed he has even specified 'WIRED IN STAR'.

Why would he wish to rule out the use of the delta configuration? What badness might result from me re-configuring into delta & running from 220/3/60? The windings don't care whether they are in star or delta - if I apply 380/3/60 in star or 220/3/60 in delta the winding still has the same voltage across it.

What am I missing?

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    Oddly I have a friend doing something similar with great success from well below 50Hz to about twice it - the good VSD inverters can be programmed to drop the effective peak voltage as the frequency drops. In reality it is modulating the mark to space ratio of a square wave but the motor windings are only heated in more or less the normal way as per the fundamental component of the waveform
    I suggest a campaign of just doing it - if you are that bothered put something in series with the windings, like 3 identical heaters. You should be able to get it spinning and verify rotation directions, and ramp up and braking times etc at quite a lot less than the full voltage if it is not loaded. I;d not be too worried about the labeling - clearly the windings are insulated from each other, all you need to do is get 3 lots of magnetic field rising and falling in the right sequence.

    If you badly overdo the voltage or underdo the frequency (more or less equivalent) the current will rise sharply more than linearly beyond a certain point, and the current limits need to be set sensibly so that the windings are not cooked.

    The other parameter to consider is the back EMF when decelerating - an over-voltage high enough to damage the inverter can occur in some cases if you try to force a dead stop unless there is somewhere for it to go (a braking resistor) in the drive arrangements.

    Mike

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    Oddly I have a friend doing something similar with great success from well below 50Hz to about twice it - the good VSD inverters can be programmed to drop the effective peak voltage as the frequency drops. In reality it is modulating the mark to space ratio of a square wave but the motor windings are only heated in more or less the normal way as per the fundamental component of the waveform
    I suggest a campaign of just doing it - if you are that bothered put something in series with the windings, like 3 identical heaters. You should be able to get it spinning and verify rotation directions, and ramp up and braking times etc at quite a lot less than the full voltage if it is not loaded. I;d not be too worried about the labeling - clearly the windings are insulated from each other, all you need to do is get 3 lots of magnetic field rising and falling in the right sequence.

    If you badly overdo the voltage or underdo the frequency (more or less equivalent) the current will rise sharply more than linearly beyond a certain point, and the current limits need to be set sensibly so that the windings are not cooked.

    The other parameter to consider is the back EMF when decelerating - an over-voltage high enough to damage the inverter can occur in some cases if you try to force a dead stop unless there is somewhere for it to go (a braking resistor) in the drive arrangements.

    Mike

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