Electric Motor Configurations

Thanks Mike.

Out of curiosity, how would one winding being reversed show itself?

I've checked for this before (by applying a small AC voltage to each winding in turn and the 'scoping the other two) but how it manifest itself if a motor with such as mistake were to be powered?

I did ask the manufacturer ,,,, and was told no.

However, this was by a Sales Person whose response was simply that if the plate said STAR then it could only be used in star. He would not enter into any technical discussion - hence my question here.

I suspect that his answer was simply "playing safe".

My old faithful Brook Motors Pocket Book says that when considering ordering a motor many things need to be considered including:

a, Frequency of starting,

b, Reversal requirements,

c, High Static Friction,

d, High Inertia Load,

e, Acceleration.

f, Limitations on starting current.

Many Brooks motors could be run on 50 or 60 Hz. supplies. The book mainly covers old traditional methods of starting and control.

Your new motor should have come with complete technical details either on a printed sheet, or details of online access to such, to allow for correct application for a given job.

One text book that I have suggests that when using square waves to supply motors an adverse effect can be created. The harmonic energy in a square wave contributes considerably to  Eddy current and hysteresis losses in motors.

Also, a surprising fact is that the peak value of a first harmonic in a square wave  exceeds that of the square wave.

Over heating motor link.....

www.gohz.com/why-vfd-driven-motor-is-hot

Z.

Also, a surprising fact is that the peak value of a first harmonic in a square wave  exceeds that of the square wave .

By a factor of 4/pi because of course when you add in the next term in the expansion at 3F, there is a down kick at the top of the wave, knocking the peak of the fundamental down. Consider this....

A series of AC voltages at 50Hz, 150Hz, 250Hz etc. with amplitudes A3, A5 A7 etc all correctly scaled. At the bottom tap we see the waveform of the fundamental sine wave only, at the next tap up  the 50Hz plus the 150Hz term, etc.

So note the voltage scales on the Y axes - the top fundamental only sine wave is swinging  +/- 1.4v pk or so. The next graph shows that plus the next largest term the 150Hz sine wave - now this speeds up the zero crossings and knocks down the peak so swing is a touch under 1.2v. The lower traces  show there is no cheating, and as we add more and more terms it just gets more square and looks more like the ringing square wave we expect in a bandwidth  limited system.
Some times flipping to the time domain view like this can be  more informative than the spectrum,,,
Mike

Out of curiosity, how would one winding being reversed show itself?
Weak torque, heating of the windings and general weirdness as winding currents not equal.
Mike.

Yep, my Brook's book says that this fault will create a similar affect to one phase being open circuit.

"Many Brooks motors could be run on 50 or 60 Hz. supplies".

All 3 phase electric motors can run on either frequency but with acceptance of the reduced kW rating, speed, efficiency and consequent, increase in running costs, they wouldn't be designed as such however, unless the international market dictates and perhaps with a larger frame size ......... Nought for Nought.

Jaymack