VFD for 7.5hp 3 phase quincy 340 compressor

I recently purchased the compressor, however I dont have 3 phase power at my shop only single phase 240. I know it might be easier to by a replacement single phase motor, however Ive also read on some of the features that I feel I could benefit from with a VFD. In particular the soft starting. The compressor has two unloader valves and a continous run valve as well.


This is the motor label




I contacted Teco/Westinghouse and they recommended the following VFD

A510-2015-C3-U

The price of the VFD is pretty close to the cost of a new motor...would I the better choice be the VFD?

A few considerations, first there are much less expensive VFDs (the Fuji below id $571), but for the most part you would need a 15Hp 3 phase input VFD and derate it for single phase use. The FRN0047C2S-2U is rated for 26A output with single phase input. You also need to look at the additional cost of a larger power input line/breaker since it is sized based on the VFD rating and not the motor. You would need to rewire the the compressor to use the low voltage input of the VFD and remove the compressor starter (contactor/thermal overload)
FRN0047C2S-2U | Fuji Electric | AC Drives

The other option if you do not need the rated CFM is to run a 5 Hp single phase motor with a smaller motor pulley which would be significantly less cost, most of the air pumps are rated over a range of Hp motors. Otherwise, I would recommend replacing the motor with a single phase model, something like the L1510t 7.5 HP 1725 RPM Baldor Electric Motor Air Compressor will run you $620-650 shipped. At the end of the day much easier and will be the least expensive. There are various vendors.
Baldor 7.5 HP Single Phase Electric Compressor Motor 215T Frame 230V 1 – compressor-source

Is the compressor the only 3 phase machine you plan on getting? If so just swap out motor with either a 5hp or 7.5hp single phase motor. 5hp should be fairly easy to find used, anything larger gets kind of scarce or pricey new. If you anticipate getting more 3ph machines, you can buy a vfd for each one, or just buy/build a rotary phase converter.

I have not recieved the compressor yet( auction purchase) but the pictures don’t show a magnetic starter on it. The only wiring I see is wiring to the motor. I don’t see any wiring on the pressure switch either... so who ever owned this before may have been running it off a vfd as well... who knows. The seller confirmed the compressor opperates correctly(we will see once it arrives) so if I were to purchase a single phase motor I would have to add in the cost of a mag starter.

The compressor I had that this one is replacing had #6 wire off of a 60 amp breaker on its own sub panel.. not sure on the rating of that panel will need to confirm. The main panel is 200amp. I need to move the sub panel due to some renovation so wiring changes and movement are required either way.

Parts of the purchase included a refrigerated dryer for the compressor as well in three phase.. I don’t know the specs on that yet so I will more than likely need a converter or vfd for that also if I do end up keeping it.

All in all I’m thinking the cost will be close via a replacement motor route( would like the cfm it’s rated for) or the vfd route.

I see this forum has a lot of info on this and would appreciate the guidance on how best to approach this.

nandomart said:

I have not recieved the compressor yet( auction purchase) but the pictures don’t show a magnetic starter on it. The only wiring I see is wiring to the motor. I don’t see any wiring on the pressure switch either... so who ever owned this before may have been running it off a vfd as well... who knows. The seller confirmed the compressor opperates correctly(we will see once it arrives) so if I were to purchase a single phase motor I would have to add in the cost of a mag starter.

The compressor I had that this one is replacing had #6 wire off of a 60 amp breaker on its own sub panel.. not sure on the rating of that panel will need to confirm. The main panel is 200amp. I need to move the sub panel due to some renovation so wiring changes and movement are required either way.

Parts of the purchase included a refrigerated dryer for the compressor as well in three phase.. I don’t know the specs on that yet so I will more than likely need a converter or vfd for that also if I do end up keeping it.

All in all I’m thinking the cost will be close via a replacement motor route( would like the cfm it’s rated for) or the vfd route.

I see this forum has a lot of info on this and would appreciate the guidance on how best to approach this.

Click to expand...

You are now at 2 machines requiring 3ph, again are you planning on more? No motor starter, pressure switch not wired, and compressor has a continuous run valve, ummm I'm thinking that is how it was used. And auctioneer says it works? I hope you got it cheap.

So let’s say I went the vfd route. Is the Fuji vfd that was recommend all that I would need? Can someone show me how to wire it up correctly?

The problem will be what you are going to do with the 3 phase refrigerated dryer, it can't be run off of the same VFD. The pressure switch is just an open and close contact, so all you would need to do is wire the VFD low voltage forward run input to the pressure valve and use it to switch on/off the VFD, pretty much the same as it would with a contactor. You may want to wire in a E-Stop or similar switch in series with the signal wire in case you want to kill the run mode. The VFD output is directly wired to the motor, the VFD is set for the motor characteristics. You probably want a 2-3 second ramp up and ramp down to minimize an over current/over voltage error from too rapid a change in speed. You would want a power disconnect for the VFD input and fusing/breaker sized to the VFD. There are specific instructions of the programming requirements needed to run that VFD on single phase under the documents section.
https://www.wolfautomation.com/medi...n/fuji-frenicmini-c2-feca-an-175-appnotes.pdf

You might call Wolf Automation and speak to their technical department as to using the Fuji in this application and recommended model. You may need to consider a DC reactor (DCR) which reduces the rated input current per the spec. sheet. This would be recommended for other three phase VFDs running on single phase.

At the end of the day, you may be better off with a RPC that could run everything. Something like a Phase Perfect which generates the third phase is also an option, but much more expensive.

so i recieved the compressor. The dryer is single phase and runs off of 120v. So I only need a power source for the compressor. I have no other 3phase equipment aside from the compressor. So my options so far are get a single phase motor and a mag switch which will be about 1k, get an RPC which will run about the same or a VFD which will also be about the same.

Im really leaning towards the VFD only for the ramp up and ramp down options....


I talked to wolf auotmation they originally recommended the TECO A510 that I posted on my orignal post and they also said the FUJI would work but that the programming was a little more complicated.

I ran by this VFD today and the label looks like it will work...can someone provide me with more input on the pros and cons of my options ?

What about building a rotary phase converter yourself, a 15-20 hp idler should be cheap and allow you to run other 3 phase equipment. If you pony start the idler with a small 120v single phase motor you can reduce the inrush amperage.

nandomart said:

I talked to wolf auotmation they originally recommended the TECO A510 that I posted on my original post and they also said the FUJI would work but that the programming was a little more complicated.

I ran by this VFD today and the label looks like it will work...can someone provide me with more input on the pros and cons of my options ?

View attachment 253713

Click to expand...

The particular VFD by ABB is a very good unit, but the major concern is if it has been sitting on the shelf/storage for 7 years the electrolytic capacitors will deteriorate and can fail when the unit is powered up.

Precautions for storage over 1 year
If the inverter has not been powered on for a long time, the property of the electrolytic capacitors may deteriorate. Power the inverters on once a year and keep the inverters powering on for 30 to 60 minutes. Do not connect the inverters to motors or run the motor. I always check the date codes of the VFD and the storage conditions when installing a VFD.

I would go with the Fuji, I assume it is the least expensive of the lot. You probably do not need 99% of the features/programming of the VFD, but not a big deal about the programming. You would only be changing a couple of parameters. Nice unit otherwise and manual is very comprehensive.

No reason to go with an RPC if you have no other 3 phase equipment, and the duty cycle on the compressor would be low relative to the RPC run time. Also the added cost of retrofitting the electrical components on the compressor.