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[carkrazed]

I keep blowing the starting capacitor on my compressor and its pissing me off. I have a phase converter and a 5hp 3 phase induction motor laying around. I'm thinking about getting a small VFD and running the compressor with the induction motor.

Anyone ever do anything like this that has some input?

[Joseph Davis]

The Allen Bradley VFDs do 110-->3 phase at a variety of voltages up to either 1.5 or 2hp motors.  Dirty cheap at under $100 on eBay. 


I'm not terribly aware of the phase converter market, but my gut feeling has been that larger capacity solutions are expensive.

[carkrazed]

The Allen Bradley VFDs do 110-->3 phase at a variety of voltages up to either 1.5 or 2hp motors.  Dirty cheap at under $100 on eBay. 

So they are essentially an electronic phase converter?

I'm not terribly aware of the phase converter market, but my gut feeling has been that larger capacity solutions are expensive.

I have a 5hp static phase converter. I could run the motor directly off of it but i'm told that static converters don't like to start compressors. Thats why I figured I could run it through a VFD. I'm not sure if that would lessen the load on the converter or not though.

[carkrazed]

This is interesting

http://www.ebay.com/itm/5HP-4KW-220-250V-VARIABLE-FREQUENCY-DRIVE-INVERTER-VFD-NEW-a2-/300660808651?pt=LH_DefaultDomain_0&hash=item4600c7dbcb

[mandrel-bends]

I've got a newer (2012) 5HP AB vfd running a 3hp grinder out at my house on single phase. The frequency output is not as clean as the output of real 3ph. In our case, the grinder actually vibrates unacceptably running on the vfd as opposed to real 3ph at one of our buildings. Also interesting to note, the VFD did not vibrate the grinder when run from 3PH.

There's a lot of data regarding vfd -> motor vibration. I never had to time to put it on the scope to try to track it down. It definitely not the same as running it on a phase converter.

One article I looked at when analyzing it: http://ftp.betamachinery.com/uploadedFiles/004_-_Knowledge_Center/Technical_Articles/Perplexing%20Variable%20Frequency%20Drive%20Vibration%20Problems.pdf

[PhilStubbs]

In to see where this goes. I have a big compressor and a 3 phase motor I'd like to combine at home

[carkrazed]

I've got a newer (2012) 5HP AB vfd running a 3hp grinder out at my house on single phase. The frequency output is not as clean as the output of real 3ph. In our case, the grinder actually vibrates unacceptably running on the vfd as opposed to real 3ph at one of our buildings. Also interesting to note, the VFD did not vibrate the grinder when run from 3PH.

There's a lot of data regarding vfd -> motor vibration. I never had to time to put it on the scope to try to track it down. It definitely not the same as running it on a phase converter.

One article I looked at when analyzing it: http://ftp.betamachinery.com/uploadedFiles/004_-_Knowledge_Center/Technical_Articles/Perplexing%20Variable%20Frequency%20Drive%20Vibration%20Problems.pdf

Does it vibrate even at low rpm?

In to see where this goes. I have a big compressor and a 3 phase motor I'd like to combine at home

I think i'm gonna try out the ching chong vfd. How many hp is the motor you have? There is a 4hp vfd from the same seller for 145.00

[PhilStubbs]

I think it's a 5hp. My pump calls for 5hp.

Looking forward to seeing your results

[Joseph Davis]

Have a surf over Automation Direct's site before going straight eBay china.  They market asian housebrands that are as good as anything else, for less.  If you don't see what you want, with regard to price or features, then try eBay.

[Joseph Davis]

bump for more discussion

[PhilStubbs]

I have no input, just a leach in this thread.

[mandrel-bends]

I didnt test low speeds as it doesn't have the needed torque without reaching full speed. From my research, it looks like certain devices have inherent resonances that are amplified badly with these devices.

I remember from my power engineering classes that these things also can push the power factor in both directions (they can alter the reactive power of the motor by making it more/less inductive). But again, haven't had the time to bend test the unit to see what its doing.

[carkrazed]

I wanna drop the hammer on that Chinese VFD but i'm not sure how if it has an input I can use for my low pressure switch.

[mandrel-bends]

Your pressure switch should be just contact closure. The VFD should have i/o you can switch for either "run" or "enable" or both by putting the proper voltage across that switch and into your vfd. I would email them for a manual.

[Joseph Davis]

I would email them for a manual.