Who has an air compressor with a phase converter.

[TMGT]

Consider an open delta transformer system. Plenty of info on google. I grew up in the HVAC industry in Phoenix AZ. when air conditioning demand grew for residential use; the power companies resorted to configuring house drops this way as only single phase power was in the streets. It had its drawbacks but worked till years later when they upgraded the utility to 3 phase. Due to harmonics I would not operate anything else except the 3 phase load it feeds. You have the motor and this is the most economic answer. If you are being inspected you will probably run into an inspector that does not understand the system as it is not common today.

Run

I looked into doing this before 3ph was ran by my house, I can't remeber all the details as it was a number of years ago but if I remeber correctly either it needed to be brought off line voltage as a new service? I was looking into a couple setups and one required new service and another required multiple transformers that only produced about 50-60% efficiency I believe?

Either way I remember the cost was prohibitive and would have been about the same cost to switch out most of my equipments motors.

Unless the motor was application specific I would be looking for a replacment single phase motor.

 

[Tractor Seabee]

I looked into doing this before 3ph was ran by my house, I can't remeber all the details as it was a number of years ago but if I remeber correctly either it needed to be brought off line voltage as a new service? I was looking into a couple setups and one required new service and another required multiple transformers that only produced about 50-60% efficiency I believe?

Either way I remember the cost was prohibitive and would have been about the same cost to switch out most of my equipments motors.

Unless the motor was application specific I would be looking for a replacment single phase motor.

60% is about there on the loss, the book says 57%. Your are basically looking at two 240V X 240V isolation transformers. Use the two transformers just for the motor circuit, just size to compensate for the loss + start inrush. Probably cost less than a phase converter and not have a complicated electronic circuitry to fail at high cost. KISS.

Ron

 

[TMGT]

I agree about a phase converter for this application, once you get into the larger motors with high start loads/ inrush it's gets pretty costly quick and not very convenient for his application.

A single phase 10hp motor with matching magnetic start is around 1k which is probably less than transformers and associated hardware and you don't have to add more things to the shop area.

Unless it's not easily done due to proprietary specs, I would just replace the motor.

 

[LD1]

Not sure just how high the start load is on this compressor that everyone keeps claiming.

It is a screw compressor, not a piston type. So the normally associated high startup issues with compressors shouldnt be an issue with a screw. This should be just like starting any other piece of 10hp equipment

 

[LD1]

For under $300 I can get a 10hp drive....dual rated 1/3ph input.....and 34a.

I think this compressor is listed at 24 or something.

But dont know weather it will work or not. I have another chinese knockoff drive (HY drives).....listed at 4kw/5hp....17a. Also listed for 1/3 phase input. But it wouldnt start a 13a 5hp motor without faulting the drive. So the application I was using it for, I downsized to a 9a 3hp and it has been flawless.

I know that if a VFD is not dual listed for 1/3 phase input you are supposed to de-rate the drive to compensate. But everything I read on dual rated inputs 1/3...is that no de-rating is needed. But my experience says otherwise.

The price jump to a 15hp VFD is pretty steep as that pushes into ore expensive brands cause it seems the knockoff china drives top out at 10hp.

I emailed the company that sells the $300 drive and inquired weather he thought it would start a 10hp / 23a screw compressor.....waiting on a reply back right now.

 

[buickanddeere]

An air compressor has different electrical demands for power quality . A large or mill is not operated at full rated power , nor is there high inertia starting loads .
rotary and static converters do not provide true 120 degree separated three phase vectors with identical voltage .

 

[Stimw]

I am running a 50 ton Scotchman Ironworker (5 hp motor) on a static converter that I built for $45. about 10 years ago.
I was also running a 15 X 54 Cincinnati Hydrashift Lathe on the same converter but sold the lathe.
Both run great!
The converter is just 2 capacitors and a relay! (instructions from the internet)

 

[CalG]

I run a 7.5H Compressor on a rather large VFD. (25hp IIRC) The VFD (Toshiba Tosvert) was purchased for small money on ebay.

The compressor pressure switch activates the VFD, which I leave powered up year round in an unheated garage space.

The VFD effectively stops the inrush "brown out" when the compressor starts up. An entirely satisfactory arrangement.

eta
The VFD does the single phase to three phase conversion also.

 

[TMGT]

For under $300 I can get a 10hp drive....dual rated 1/3ph input.....and 34a.

I think this compressor is listed at 24 or something.

But dont know weather it will work or not. I have another chinese knockoff drive (HY drives).....listed at 4kw/5hp....17a. Also listed for 1/3 phase input. But it wouldnt start a 13a 5hp motor without faulting the drive. So the application I was using it for, I downsized to a 9a 3hp and it has been flawless.

I know that if a VFD is not dual listed for 1/3 phase input you are supposed to de-rate the drive to compensate. But everything I read on dual rated inputs 1/3...is that no de-rating is needed. But my experience says otherwise.

The price jump to a 15hp VFD is pretty steep as that pushes into ore expensive brands cause it seems the knockoff china drives top out at 10hp.

I emailed the company that sells the $300 drive and inquired weather he thought it would start a 10hp / 23a screw compressor.....waiting on a reply back right now.

I guess I read that wrong,
Seem pretty cheap as I assume it's a VFD, most higher loads like compressors need a much larger drive, 10hp will probably need a drive for about 3times it's rating or more.
Even though it's a screw drive it still has a high start load and inrush is a large factor, all the compressors at every shop I work in are now screw. So much quieter.

 

[crazyal]

You could try to reduce the inrush current. Most compressors have an unloader. The problem is that the pipe between the compressor and check value is short and the compressor quickly gets loaded while it's still ramping back up to speed. You could take it a step further by having the compressor just vent to atmosphere for a few extra seconds with an electric valve before closing so the motor starting up and the load of compressing air are separated.