VFD size

[colin hamiltonParticipant @colinhamilton16803]

Posted by Harry Wilkes on 06/11/2021 14:52:03:

Colin before running out and buying a new VFD check that P12 is set to around 8 amps

H

This is getting interesting. I couldn't work out why no value or range was stated. I'll have a look in the morning (my lathe isn't get at my home). It states somewhere I can change the display to motor current. Would that be this value?

[colin hamiltonParticipant @colinhamilton16803]

Posted by Robert Atkinson 2 on 06/11/2021 14:54:50:

What is the actual current setting on the VFD? This is P12.0 (motor) and P12.5 (drive). The tables you show say 5A set but that a 2.2kW VFD output is 10A max.

Robert G8RPI.

Thanks for the advice. I'll check in the morning

[Anonymous]

Posted by DC31k on 06/11/2021 12:54:46:

The challenge using a 2-speed motor with a VFD is that it is not possible to configure the motor to accept 230v three-phase.

…………

As I understand it, the most common way for a two-speed motor to be configured is 'Dahlander wound'.

Fair point, although the motor will still run in star. Just that the power will be down as the phase currents will be lower than when running from 415VAC.

I've got two machines with 2-speed motors, the horizontal mill and the repetition lathe. The motor on the repetition lathe only changes the number of poles. Slow speed only halves the speed and hence is half the power, vis 1hp and 0.5hp.

The horizontal mill is rated 5hp in high speed and 4hp in low speed. So as well as doubling the number of poles it changes from star to delta when going from high to low range. I'm not convinced the motor is arranged according to Dahlander. I suggested this a while ago on the forum and was told in no uncertain terms that it was unlikely to be a Dahlander configuration. To change from high to low speed two knobs need to be changed. One standard electrical switch on the electrical box and one (which I an sure is electrical) on the column of the mill under the speed change levers.

Andrew

[Steve RParticipant @steverichardson2]

Most? VFDs should allow setting two frequencies as the main output (you can then use one or the other – high or low). You can use that to create your two speeds when connected to a 'single speed' 3 phase motor coupled with the original variator – and you then have your variable speed and two speed ranges. This possibly has some power limitations at low frequency – but I have not encountered issues with my lathe that is set up this way.

the other option is If you remove the variator and original two speed motor, and replace with a conventional single speed 3 phase motor connected to a two speed counter shaft/pulley arrangement. this coupled with the VFD, gives two speed ranges plus convenience of variable speed via VFD.

cheers

Edited By Steve Richardson 2 on 11/11/2021 09:48:31

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