3-Phase vs Single Phase Equipment

[Michael Zerance]

My new location does not have 3-phase service so I will be installing a phase converter to power my sanders, spray booth fan, and some other smaller pieces of equipment. I am leaning hard towards the Phase Perfect.

For new equipment purchases, when there is an option for either single phase or 3-phase equipment, which would be preferable? Is there a benefit to running 3-phase through a phase converter versus just wiring a single phase unit direct to the panel?

Specifically, I am looking at buying a new Oneida 5hp dust collector and they have single phase or 3-phase available for the same price. The rep from Oneida recommended the 3-phase but he didn't seem to think it really mattered. I'm considering the single phase because the wide belt has a max load of 54 amps and the Oneida has a running load of 12 amps which puts me above the 64 amp output of the 20hp Phase Perfect and the rep from Phase Perfect recommended not going above 60 amps. I realize that under normal operations the amp draw on the wide belt would be significantly less so it shouldn't be an issue but I have the option and I don't think it's worth the potential risk of overloading the Phase Perfect.

Is there any benefit of going with the 3-phase in this situation?

[Kevin Jenness]

Single phase motors have capacitors and centrifugal switches to get started, so more complex and potentially prone to failure. Other benefits to three phase equipment are smaller conductors and a larger pool of used industrial equipment unavailable to users with only single phase supply.

In your situation I could see going either way. If you have or plan to have employees running multiple three phase machines you should probably look at a larger converter and go with the three phase dust collector. Phase Perfect has a great reputation but for most machinery a rotary unit will work perfectly well and be less expensive. If you really want the digital converter (e.g. for cnc), don't expect to have any larger demand than 60A and don't want to invest in a larger converter go with the single phase Oneida. Just be aware that the start circuit on that (essential) system is a potential failure point.

[derek labian]

Is there any benefit of going with the 3-phase in this situation?

I looked at the same option a few months back.

I would say go single phase. In many cases 3ph would be preferable for the reasons already listed. There may be a HP gain too depending on the equipment, but not with Oneida. In this case you gain little, add extra cost due to inverter capacity (now or in future), and If the motor fails you can find a 5hp to replace it either way.

i would suspect they provide that option for shops with 3PH from the utility.

Good luck.

[Mike Henderson]

I agree with Derek. If you had three phase coming into your shop, go three phase motors. But if you have to convert, go single phase.

Mike

[Leigh Betsch]

I have a few 3 phase machines. A rotary phase converter and a VFD. I like the 3 phase options and it works well for me. But, I think resale on single phase machines is probably higher if you ever want to sell something.

[Curt Harms]

If you really want the digital converter (e.g. for cnc), don't expect to have any larger demand than 60A and don't want to invest in a larger converter go with the single phase Oneida. Just be aware that the start circuit on that (essential) system is a potential failure point.

I could maybe see some advantage to 3 phase on a dust collector. As Kevin said 3 phase motors don't have the failure points of single phase. I'd suspect dust collectors get started more times in a day than any other single piece of equipment so may be more prone to failure.

[Jason Roehl]

My new location does not have 3-phase service so I will be installing a phase converter to power my sanders, spray booth fan, and some other smaller pieces of equipment. I am leaning hard towards the Phase Perfect.

For new equipment purchases, when there is an option for either single phase or 3-phase equipment, which would be preferable? Is there a benefit to running 3-phase through a phase converter versus just wiring a single phase unit direct to the panel?

Specifically, I am looking at buying a new Oneida 5hp dust collector and they have single phase or 3-phase available for the same price. The rep from Oneida recommended the 3-phase but he didn't seem to think it really mattered. I'm considering the single phase because the wide belt has a max load of 54 amps and the Oneida has a running load of 12 amps which puts me above the 64 amp output of the 20hp Phase Perfect and the rep from Phase Perfect recommended not going above 60 amps. I realize that under normal operations the amp draw on the wide belt would be significantly less so it shouldn't be an issue but I have the option and I don't think it's worth the potential risk of overloading the Phase Perfect.

Is there any benefit of going with the 3-phase in this situation?

Are you sure the 54A rating on the wide-belt sander is 3-phase? And at what voltage? At 208V, that’s a 20hp motor.

[Michael Zerance]

Are you sure the 54A rating on the wide-belt sander is 3-phase? And at what voltage? At 208V, that’s a 20hp motor.

Correct, it's a 20hp machine.

[Michael Zerance]

Single phase motors have capacitors and centrifugal switches to get started, so more complex and potentially prone to failure. Other benefits to three phase equipment are smaller conductors and a larger pool of used industrial equipment unavailable to users with only single phase supply.

In your situation I could see going either way. If you have or plan to have employees running multiple three phase machines you should probably look at a larger converter and go with the three phase dust collector. Phase Perfect has a great reputation but for most machinery a rotary unit will work perfectly well and be less expensive. If you really want the digital converter (e.g. for cnc), don't expect to have any larger demand than 60A and don't want to invest in a larger converter go with the single phase Oneida. Just be aware that the start circuit on that (essential) system is a potential failure point.

After your comment, I looked into a 40hp rated rotary phase converter. It's recommended for 50 amps of 3 phase output but it rated at a maximum of 98 amps so it seems like it would work well for my situation. In addition, like you stated, it's significantly less expensive.

[Michael Zerance]

Thanks for the replies, fellas.

[Bill Dufour]

A three phase dust collector should be able to be used as an extra idler motor for a converter setup. I know a big disk sander works that way. I am unsure if the load on a dust collector allows it to be used as an idler or not.
A three phase dust collector means you never have to climb a ladder and check capacitors or starting switches.
A rule of thumb is any new or used three phase equipment is better quality, industrial long life stuff. Single phase you have to know what you are looking at to only buy good stuff.
Bill D

[Jonathan Jung]

3ph motors can handle starting/stopping (cycling) more often than 1ph motors. At least that's what I've been told by a few in the motor industry. My Clearvue motor started on fire, was not replaced under warranty due to "starting it more than 4x per hour", which is not stated anywhere on their site or user guide. The reason given was that starting it too often overheated the starting capacitor, leaked the oil into the windings and caught fire.

[Mike Henderson]

3ph motors can handle starting/stopping (cycling) more often than 1ph motors. At least that's what I've been told by a few in the motor industry. My Clearvue motor started on fire, was not replaced under warranty due to "starting it more than 4x per hour", which is not stated anywhere on their site or user guide. The reason given was that starting it too often overheated the starting capacitor, leaked the oil into the windings and caught fire.

The reason there's a recommendation on the number of starts of a motor is that there's a high starting current through the motor. This generates heat which can be dissipated by the motor fan after the motor gets running. If you let the motor run for a reasonable time, the temperature stabilizes. I would think that the worst case would be frequent starts and short runs.

I start my dust collector multiple times an hour and never worried about it overheating. If you have a good quality starting capacitor it should not fail that easily. Some motors, especially those made in Asia, come with very cheap capacitors which are prone to early failure.

Mike

[Malcolm McLeod]

...there's a high starting current through the motor. This generates heat...

+1. And the bigger the motor, the slower the heat dissipates. We run a lot of 400Hp motors and programmatically limit them to 3 starts/hr; 150Hp :: 5 starts/hr.

[Jonathan Jung]

Agree. The motor that caught fire was a US-made Baldor 5hp 22fla, and I was starting it up to 8 times an hour before I was schooled.