RPC vs. VFD for Air Compressor

I am looking to purchase a 15 hp 3 phase 230 volt air compressor to use at my house which has single phase. Am i better off building a rpc or should i get a vfd to run it. I want to supply the "cleanest" voltage to the motor. Thanks.

The VFD in that rating will be more expensive than the compressor. A three phase compressor will work well with a carefully built RPC. Regards, Clark

That's a lot of air around the house! ;-)

I have my 5hp CH compressor on a 20HP VFD (phase converter over rated ebay purchase for small money)

The best part of the deal with the VFD is no inrush brown out. My neighbors could always tell when the compressor turned on when supplied with the RPC.

With the VFD, there is none of that.

The VFD stands for Variable Freq Drive. You will not be varying the frequency. Seems like a waste
of VFD if you spend a lot. But it will be quiet. The compressor will make a deal of noise when charging
so a quiet VFD probably is not going to make much difference.

A RPC built by you will be less expensive. The RPC will only be on when charging the tank. The
RPC will be more reliable.

rons said:

The VFD stands for Variable Freq Drive. You will not be varying the frequency. Seems like a waste
of VFD if you spend a lot. But it will be quiet. The compressor will make a deal of noise when charging
so a quiet VFD probably is not going to make much difference.

A RPC built by you will be less expensive. The RPC will only be on when charging the tank. The
RPC will be more reliable.

Click to expand...

A VFD could be used to decrease the RPM of the motor allowing you to run the compressor more quietly, which could be a huge plus.

snowluck2345 said:

A VFD could be used to decrease the RPM of the motor allowing you to run the compressor more quietly, which could be a huge plus.

Click to expand...

The tank would take longer to charge. In most situations the air supply demand will keep that
motor running and running. Plus not. Quiet is not the issue, the frequency of the pump noise is what
will change. The tradeoff is faster speed and tank charge, or slow speed and longer tank charge with
a low frequency pump sound with longer duration. Who would want a starved air supply. Probably if
have infrequent use and like a zen setting in the shop.

rons said:

The tank would take longer to charge. In most situations the air supply demand will keep that
motor running and running. Plus not. Quiet is not the issue, the frequency of the pump noise is what
will change. The tradeoff is faster speed and tank charge, or slow speed and longer tank charge with
a low frequency pump sound with longer duration. Who would want a starved air supply. Probably if
have infrequent use and like a zen setting in the shop.

Click to expand...

Air demand in a home shop situation for a 15 hp air compressor will not keep the unit "running and running" unless there is something special going on. and in that case, bump the VFD frequency up to 70hz and enjoy the rapid recovery! ;-)

ps, I absolutely enjoy the rhythmic pulse of a slow speed air compressor. If not for the VFD on my own unit, I would have opted for single phase motor with an oversized compressor pulley. Just to slow things down.

Hi

I have a Quincy 7.5 HP 80 Gal 3phase with a 15HP Teco VFD. I choose this arrangement for two reasons. First I did want to use the slow start capability of the VFD ( I have three others on machines). You can put an AMP meter on it and watch it slowly climb ( 6sec) to full amps. Second, the Quincy unit has a splash lubricator and is designed to work with other applications, according to their specs I can run it down to about half the speed used for normal operations. Makes it real nice, you can carry on a conversation while it is running. 95% of the time I run it slow, when I am blasting I crank it up. When I purchased this unit the single phase unit with the starter was more expensive than the three phase. The difference in price paid for 75% of the VFD.

I do not know what kind of unit you are purchasing but make sure you can slow it down. If it has splash lubrication you should look at the spec sheet, even if it has an oil pump for lubrication there may be a minimum RPM for it to work properly.

Bob

CalG said:

Air demand in a home shop situation for a 15 hp air compressor will not keep the unit "running and running" unless there is something special going on. and in that case, bump the VFD frequency up to 70hz and enjoy the rapid recovery! ;-)

ps, I absolutely enjoy the rhythmic pulse of a slow speed air compressor. If not for the VFD on my own unit, I would have opted for single phase motor with an oversized compressor pulley. Just to slow things down.

Click to expand...

I think your statement cannot be valid unless the size of the tank is known. When I paint with my HVLP guns with a 120 gallon tank it sure sounds like something "special" is going on.

On the other hand if you are removing a few tire wheel bolts with a air tool then dialing down the compressor motor is ok.