220V single phase to 380V three phase

[mekanik]

Please excuse my ignorance, but can you tell from the motor nameplate IF this is infact 3 phase ?.
The guy in the Netherlands said motor was strong on 380V no 250.
I have been assuming(a bad thing to do with electrics) because of the 380V that it was 3 Phase.
Is there anyway i can check it with a multimeter, I will also need to identify the high & low speed windings, as it's looking like i will be running single speed for the imediate future(just desperate to get it making chips again)
PS that would have been £700 +VAT
Regards

[JohnHaine]

Hard to make much of the photo as some of the leads seem to be labelled with their colours and some with something else! Could you possibly say what the labels say on each lead with its colour? - that might be helpful.

There seem to be 7 wires on a 3-phase motor, so I would guess that one, possibly the green/yellow one, is ground and connected to the frame - easy to check. I don't think there could be 7 wires on a single phase. The reason why 380v is associated with 3 phase is because that's the phase-to-phase voltage, which corresponds to 230v phase-to-neutral. Your home single phase supply is usually one phase of a 3 phase supply with a neutral.

That leaves 6 more wires. Measure the resistance between them in pairs. If you are lucky you will get 3 pairs that look nearly shorted but each isolated from the other two. That would mean a simple 3-phase winding that you could easily connect in delta to run on 230v but since the plate indicates dual speed then probably not so lucky.

The only other thing to do is measure all the resistances from each terminal to the other 5 - not so bad , I think there are only 15 measurements to make. From those we might be able to figure out how the windings are configured and which wire goes where.

[mekanik]

Thanks for that John, I think i might have been clutching @ straws with this it actually came with a mains plug and that's 5 pin.
I reinstated the single phase switchgear so i get my mill attachement working and the single phase switch is different from the one supplied with the new motor.
I will try and fathom out the 2 sets of windings from the switch assemby.
Thanks again John for your time and patients.
Regards
Mike

[mekanik]

Sorry about the slight delay with the winding readings, was trying to get the motor mounted yesterday and discovered a slight problem.
John
The labels on the motor leads were only to identify the connection to the switch terminals, the issue with the cable colouring is due to what appears to be some form of insulation coating that has discoloured with the passing of time.
Readings as follows.

V4 Blue to V2 White 85.4 Ohm
V4 Blue to U2 Yellow 47.0 Ohm
W2 Green to W4 Grey 85.4 Ohm
W2 Green to U4 Red 49.4 Ohm
U4 Red to U2 Yellow 85.4 Ohm
W4 Grey to V2 White 46.5 Ohm

[JohnHaine]

What you have I think is a Dahlander connected motor.

https://en.wikipedia.org/wiki/Dahlan...changing_motor



I think to run in low speed mode you connect the 3 phase wires to U4, V4, W4. For high speed U2, V2, W2, and connect together the suffix 4 terminals. Both ways the motor will expect to see 380v for full power so will give lower power at 230v.

And is the 7th wire connected to the frame (i.e. ground)?

[mekanik]

Thanks for that John, very helpfull.
Is there a prefered speed, ie high or low speed as its looking like i can't use the original mechanical switch.
Can i assume that the three phase motor even on the low power will be similar to the power of the original single phase motor.
Thanks again John
Regards
Mike

[JohnHaine]

What speed was the single phase motor?

[mekanik]

original motor was 2 speed, change over sequence was start on low speed and then press the double speed button 1400 & 2800 rpm
When i was looking @ inverters i searched for "220V single phase to 380V three phase and did find a couple.

[JohnHaine]

According to the motor plate the power is larger at 2800 than 1400 so if power is what you want use 2800, i.e. the "pseudo star" connection (second option). I couldn't comment on how the power would compare to the single phase motor since I don't know what power that was. However if you run the motor on 230v rather than 380v you will get lower power than the plate rating, but I believe that you can recover the torque by reducing the frequency to around 30Hz. If you can get a 380v inverter of course it won't be a problem.

Just to emphasise, my connection recommendation is based on what I can make out of the motor plate and the Wiki article, though I've used VFDs in several machines I haven't seen a Dahlander-connected motor and I don't remember it from my electrical machines course (but that was 53 years ago...).

[mekanik]

Thanks John
If i wire it for 2800 rpm would it be possible to reduce the speed down to 1400 without it stalling, to be honest i usually only use 2800 for centre drilling small holes and any polishing.
Does the cable comming from the VFD to the motor have to be shielded as i don't want them next door complaining when i use the machine.
any recommendations for cable size.
I wasted a lot of time trying to get the motor mounted but couldn't do it without a radical re-arrangement so i removed the end covers and swapped them with the one's off the single phase motor and there's a slight mod to do but it's only a matter of some pieces of angle iron(body of the three phase motor is shorter than the single phase)
Thanks again John,
just have to hope that the motor is OK.
Kindest Regards
Mike