Adjustable Speed Drive Controller vs. Phase Convertor

[laketime]

I have a customer that wants to run a 3 phase machine in his single phase only shop. He has a Square D Altivar 58-TRX on the wall but he doesn't know why he has it. I did a little research and it says its an adjustable speed drive controller. Without getting too technical; Can that be used to run a three phase motor from single phase supply? If not (which I don't think it can) what should be the product we should be looking toward?

 

[petersonra]

I have a customer that wants to run a 3 phase machine in his single phase only shop. He has a Square D Altivar 58-TRX on the wall but he doesn't know why he has it. I did a little research and it says its an adjustable speed drive controller. Without getting too technical; Can that be used to run a three phase motor from single phase supply? If not (which I don't think it can) what should be the product we should be looking toward?

a lot of smaller VFDs can be run with single phase input, but they will have a lower than rated available output. You would have to look at the manual for the specific drive.

 

[Jraef]

Technically, all VFDs are capable of running a 3 phase motor from a 1 phase source. If de-rated to 1/2 of their output current. But for various reasons, not all mfrs allow you to do this. Most drives come with phase loss protection and a few do not provide a way to disable that, which renders them unusable as phase converters. Check the manual for that drive and the current rating to see if it will work for you. If so, let us know and you will get more info on how to use, and not use, that drive for this.

 

[Besoeker]

Technically, all VFDs are capable of running a 3 phase motor from a 1 phase source. If de-rated to 1/2 of their output current.

Actually, some manufacturers make single phase input three phase output VFDs. They designed for that purpose and rated accordingly.
Another option would be a UPS, again many of which are rated to operate from single phase with a three phase output. Starting a motor needs to be considered but those I've dealt with have a "walk in" feature.

 

[StarCat]

Case History

Case History

I once oversaw a Guest Ranch that had a small commercial laundry to take care of all the linens etc.
It was a 3 phase line [ Milnor Machines ] being run from a single phase panel plus a phase converter.
2 of the machines were older generation. One of the machines had a VFD inside which in fact did not care for the " wild " phase supplied by the phase master converter. It would often times give a manual reset fault which required removing the back panel of the machine to clear.
Interestingly enough, Milnor Tech Support had me convert said unit to single phase supply and sent me an over rated VFD as described above to then run the 3 phase load. I think the motor load was 3HP and the drive was maybe 5HP or there abouts.
A dynamic braking resistor was also added. The machine ran perfect from that point on.

Now with respect to the quirks of the phase master converter.
The 2 older series machines did not care for having the " wild " leg off the phase master feeding the control transformers or rectifiers.
The point in all this being that depending on what you may be running, phase generators can be a bit of a problem which requires sorting out.
Also I came by a small phase generator which was in a storage building we took over in the recent past. Said unit looks brand new and could be had cheaply.

All the best

 

[kwired]

I once oversaw a Guest Ranch that had a small commercial laundry to take care of all the linens etc.
It was a 3 phase line [ Milnor Machines ] being run from a single phase panel plus a phase converter.
2 of the machines were older generation. One of the machines had a VFD inside which in fact did not care for the " wild " phase supplied by the phase master converter. It would often times give a manual reset fault which required removing the back panel of the machine to clear.
Interestingly enough, Milnor Tech Support had me convert said unit to single phase supply and sent me an over rated VFD as described above to then run the 3 phase load. I think the motor load was 3HP and the drive was maybe 5HP or there abouts.
A dynamic braking resistor was also added. The machine ran perfect from that point on.

Now with respect to the quirks of the phase master converter.
The 2 older series machines did not care for having the " wild " leg off the phase master feeding the control transformers or rectifiers.
The point in all this being that depending on what you may be running, phase generators can be a bit of a problem which requires sorting out.
Also I came by a small phase generator which was in a storage building we took over in the recent past. Said unit looks brand new and could be had cheaply.

All the best

Good point, I have never seen a rotary or static phase converter that had perfect, and often wasn't even close on phase balance. I'm guessing you probably do not want motors to be loaded to their full load rating either when running from such converters, unless maybe you have somewhat limited duty cycles. You must also make sure any control power is connected to the incoming lines and not the manufactured third phase or you will subject the controls to voltage well out of acceptable range of the incoming voltage.

 

[texie]

Good point, I have never seen a rotary or static phase converter that had perfect, and often wasn't even close on phase balance. I'm guessing you probably do not want motors to be loaded to their full load rating either when running from such converters, unless maybe you have somewhat limited duty cycles. You must also make sure any control power is connected to the incoming lines and not the manufactured third phase or you will subject the controls to voltage well out of acceptable range of the incoming voltage.

Yes, phase converters have their drawbacks. If you are powering, say just 1 motor, that's maybe OK for many applications. But when need to power something like the Milner equipment mentioned or similar I have used a product that solves many of the issues with this. Pretty pricey but impressive: http://www.phasetechnologies.com/

 

[Rick Christopherson]

I have a customer that wants to run a 3 phase machine in his single phase only shop. He has a Square D Altivar 58-TRX on the wall but he doesn't know why he has it. I did a little research and it says its an adjustable speed drive controller. Without getting too technical; Can that be used to run a three phase motor from single phase supply? If not (which I don't think it can) what should be the product we should be looking toward?

You didn't give a complete model number for that drive, but some of them are pre-rated for single phase input without requiring derating. I looked up the Altivar manual and was surprised to see that they make some pretty large VFDs that are still rated for single phase input. The input rectifier needs to be oversized when fed from single phase, as compared to its 3 phase equivalent.

Generally speaking, any motor below 5 or 7 hp will be less expensive to set up with a VFD than with a phase converter. The cost of lower power VFDs is so low that it's almost no longer worth entertaining even building your own converter, let alone the cost of a store-bought converter.

Don't get fooled by the low cost of a static converter. With very few exceptions, they really have nothing to do with phase conversion. They are simply motor starters, and once the motor is spinning, the static converter completely drops out of the circuit and the motor is left to run on single-phase.

 

[Rick Christopherson]

Yes, phase converters have their drawbacks. If you are powering, say just 1 motor, that's maybe OK for many applications. But when need to power something like the Milner equipment mentioned or similar I have used a product that solves many of the issues with this. Pretty pricey but impressive: http://www.phasetechnologies.com/

I believe that your opening statement above relates to static converters, not rotary converters. A static phase converter, which as I said above, isn't really a phase converter at all, can operate only a single motor. However, a rotary phase converter actually becomes more efficient as in powers more and more motors. That's because each additional motor tends to partially serve as an idler motor.

 

[Besoeker]

The input rectifier needs to be oversized when fed from single phase, as compared to its 3 phase equivalent.

Don't forget the bucket capacitors being fed with lumpy single-phase rectified instead of relatively smooth rectified three-phase.