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I'm converting an old milling machine (Optimum F40E) machine to be driven with a VFD, and I have it working. The head is a geared head, and with correct settings (torque compensation) in the VFD I can overcome the startup torque in the gear-train when the machine is shifted into the "high speed" gear.

There is continuity between all six terminals in the terminal box on the motor.

I measured the resistance between U/V/W 1..6 and found something unexpected. The housing for the wiring doesn't contain any bus-bars, so the motor must be internally wound a specific way.

Here's the motor info plate:

enter image description here

The resistance between the terminals is as such (I measured every terminal combination explicitly, even though this is redundant)

enter image description here

Is this a star, or delta internal configuration, or is the motor damaged?

PStechPaul
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Lee Hambley
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    I think there's an error in your second column at the bottom. – Andy aka Jul 05 '23 at 11:45
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    there is an error in "the row terminal designations" (the last one, by the looks of it), and I don't believe the value column #6, row #4 value. – greybeard Jul 05 '23 at 17:45

1 Answers1

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It's a 'Dahlander' two-speed, pole-changing motor.

enter image description here

The windings are 'delta-connected' for 1400 RPM and 'double star-connected' for 2800 RPM.

vu2nan
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  • Many thanks for pointing it out, greybeard. Was burning the midnight oil and uploaded the wrong version of the drawing! – vu2nan Jul 06 '23 at 03:17