Help Wire 3 Phase 2 Speed Motor

[Mark HallParticipant @markhall37441]

Of course if you decide to wire it to low voltage terminal you will have to set the correct voltage in parameters

[Mark Hall]

On Mark Hall Said:  is it possible to use a single phase in & 3 phase 380V out VFD for this?, …

Can you provide a circuit diagram please?  Is it different from Allan’s compromise, in which the 2-speed motor is wired for one speed only and driven by a VFD of appropriate voltage?

Wiring one VFD to a single motor is straightforward.   Using one VFD to power two motors is asking for trouble, and so is switching a VFD’s output.  I tried to explain why it’s unwise to connect a VFD to a Dahlander motor and switch the windings as the machine was originally configured.  No problem when the supply is true 3-phase, but unwise when 3-phase is generated electronically.   Julie found my explanation muddled, and, if I gave the impression speed is related to impedance, she’s right!  Impedance is nothing to do with speed, other than indirectly due to how the motor is wound.  I was trying to explain why ordinary VFDs don’t like load impedances that jump about due to different windings being connected, and especially dislike their outputs being switched. Sorry I failed, and no-one else has tried!

How risky depends on what’s inside the VFD.  So far I’ve not found an inexpensive VFD that supports mixed loads and/or switching.  Those that do are expensive.  Might change because the cost of electronics tends to drop, but so far, best not to risk mixed loads and/or switching. Check the spec if it’s wanted.

Allan’s solution keeps his VFD happy by strapping the Dahlander’s windings permanently into single speed.  Then there’s no need to switch the VFD, and the circuit becomes conventional, hurrah!

Speed is controlled by varying frequency, not voltage, and the VFD voltage is chosen to match the motor.

Apologies if I’ve misunderstood, but, if proposing something new, how would Mark wire Ub, Vb and Wb?

Dave

 

 

[Mark HallParticipant @markhall37441]

Hi

OK so I I decided to test this out today with this 415V 2 speed motor picturediabove. I did a bench test & it worked so i put it on on a lathe to run it through the RPM speed. I first connected the low speed terminals 1U 1V 1W to the VFD & set the voltage to 230V & maximum Amps 4.3A & selected high gear & i got the lathes rated 1500rpm (obviously its geared) the motor is very smooth.
Next test  i swapped the terminals & connected the high speed motor wires  2U 2V 2W to the VFD & set the voltage to 380V & the maximum Amps to 6.1A & got 3000rpm, again very smooth, I then machined SS for 30 minutes & checked the motor & its cold. Athough i connected it separately there are settings in the parameters to programme both & use them using the M.FUNC button on this VFD so it switches between low/high speed setting but that is for another day as it 6pm now & tea time.

Bear in mind I already have a 2.2kw inverter rated dual voltage motor that I used for this lathe & its a great motor but the 415v pictured is running alot smoother so I’m temped to keep it on the lathe now & use the new one for another project. Wish I new this befor I purchased another motor but its always good to have a spare. There has to be a downside somewhere,  maybe decreased torque IDK but it’s working.

[Mark HallParticipant @markhall37441]

Here is the VFDs I been using , they are available in both  240v in 230V 3 phase out & 240V in & 380V 3 phase out & its the latter I used for this test you can set the voltage above 380V in the parameters but i stuck to 380V max. There is also a external display that is available for this model. I’ve never had a issue with them & all three i have come from there & my linear scales & DRO, they are cheap but the important thing is they work as advertised.

There was somone on the hardinge forum that connected & used a VFD on his hardinge 415V precision 2 speed motor using a drum switch to change the speed & adjusted the parameters to run it one way or the other. I have not go that far, I’ve only tested it wired to the VFD one way or the other. These are 2-3HP motors & maybe there are torque losses but I can see or feel them on the lathe, if there is perhaps it would be more noticeable on a lower HP motor. There are torque compensation parameters on the VFD but I have no experience using them. 

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