VFD vs RPC for compressor
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  1. #1
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    Default VFD vs RPC for compressor

    Good morning all,
    Looking for input based on experience here.

    I acquired a 15HP 3phase Ingersoll Rand compressor for a decent price, but don't have native 3 phase at our shop. The shop is 120/240v and the compressor is set up for 208/230/460v.

    I'm very electrically minded, and run a company with several electricians on staff but even they aren't sure what to do.

    What is my most efficient option to power this unit? From research it appears a 30HP VFD (50% derate to go from 1 to 3 phase) may be the ticket, but just wondering if anyone has a specific manufacturer/model they've had success with.

    I've considered the RPC idea as well, but I don't have anything else in the shop big enough to justify it over a VFD. Any mill/lathe we buy in the future will be small enough to use a VFD with. I also really like the idea of being able to soft start and tweak frequency on demand etc.

    Cost isn't really an object. I just want something that won't be super inefficient. It'll be running 3-4 hours each day.

    Any input offered will be appreciated!

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    I have run the shop 7 hp air compressor on a 20hp Toshiba TOSVERT VFD for over ten years. It works great. I appreciate the soft start the most.
    The Toshiba line offers easy parameter settings from a lap top. Handy.

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    Thanks for the reply.

    Looking through options it's hard to find stuff that is clearly suitable...

    I'm wondering, is this an acceptable solution? PC1-150, 15HP Phase Converter

    It's rated output current is 45A, and the FLA on the compressor is 42A. The one thing I'm not sure about is the whether the derating is assumed because it's advertised specifically as a single to 3 phase converter, or whether I should be derating on top of the output current.

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    It's too much to keep up with all the different equipment. Check with the distributor for better assurance.

    ETA

    Reading through the manual, That drive looks like a good one. But I'm no electronics /Drive designer. Check with JST and others here on the forum.

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    Usually you derate VFD only when it's designed for 3-ph. input, but you feed it with a single phase.

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    Depending on the duty cycle of the compressor/work hours, you may need to be running the RPC for hours on end, you need the space and need to deal the noise, etc. Depending on the compressor details and your air consumption needs, it may not be cost effective option to add 3 phase vs. say a duplex compressor with two 5 Hp motors. You also have limitations as too the compressor Hp/Speed range, so reducing the speed may need a pulley ratio change, soft start doesn't really add much with an unloader.

    Probably the simplest , quiet and most energy efficient (98.7%) route would be to run it off of a Phase Perfect PT020 (20 Hp). At idle it consumes around 70W. Not inexpensive, but if you were to go with a 30 Hp VFD and derate it for single phase input, at the end of the day you may not be saving very much after all the installation costs. You could go with a PT030 (30HP) if you were to add other 3 phase equipment down the line. If you are using something like an iron worker or other equipment like CNC, the Phase Perfect would be a more ideal choice and keep your equipment plug and play.

    Phase Perfect

    Not sure if the SpeedStar VFDs are available and if they would meet electrical codes, per previous discussion. A compressor is a difficult load for a VFD, you would be better off with a current generation 30Hp VFD derated to run on single phase. You would need to add a DC choke if not incorporated into the VFD, may need a line filter, etc. $$.

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    Quote Originally Posted by PTSCummins View Post
    Cost isn't really an object. I just want something that won't be super inefficient. It'll be running 3-4 hours each day.

    Any input offered will be appreciated!
    How large is the storage tank?
    Is there a CFM number required?

    I think your number of 30Hp is too much.

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    Quote Originally Posted by rons View Post
    How large is the storage tank?
    Is there a CFM number required?

    I think your number of 30Hp is too much.
    Tank is 120 gallons, rated output is 50CFM at 175PSI.

    We will rarely be using full output, so the plan was to set the vfd up on a low load setting for most of the time then have a switch to flip it over to high demand mode.

    The only time we'll probably come close to maxing output is sandblasting equipment etc.

    Some of the Hitachi 25hp vfds have a rated input current of 79A, which would leave a little bit of overhead (FLA conveted to single phase is 72A).

    We may add other equipment in the future, but nothing with this size spindle so I'm not considering a phase perfect at this time. They're just insanely expensive at this point.

    Sent from my SM-G973W using Tapatalk

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    Quote Originally Posted by mksj View Post
    Depending on the duty cycle of the compressor/work hours, you may need to be running the RPC for hours on end, you need the space and need to deal the noise, etc. Depending on the compressor details and your air consumption needs, it may not be cost effective option to add 3 phase vs. say a duplex compressor with two 5 Hp motors. You also have limitations as too the compressor Hp/Speed range, so reducing the speed may need a pulley ratio change, soft start doesn't really add much with an unloader.

    Probably the simplest , quiet and most energy efficient (98.7%) route would be to run it off of a Phase Perfect PT020 (20 Hp). At idle it consumes around 70W. Not inexpensive, but if you were to go with a 30 Hp VFD and derate it for single phase input, at the end of the day you may not be saving very much after all the installation costs. You could go with a PT030 (30HP) if you were to add other 3 phase equipment down the line. If you are using something like an iron worker or other equipment like CNC, the Phase Perfect would be a more ideal choice and keep your equipment plug and play.

    Phase Perfect

    Not sure if the SpeedStar VFDs are available and if they would meet electrical codes, per previous discussion. A compressor is a difficult load for a VFD, you would be better off with a current generation 30Hp VFD derated to run on single phase. You would need to add a DC choke if not incorporated into the VFD, may need a line filter, etc. $$.
    When I estimated a phase perfect it came in the $4400 range (CAD after landing). So far I've gotten a quote back for $2480 for a SJ700.

    I agree soft start won't be super necessary, but the motor on this compressor can be run fairly lowe without oiling issues. That's more what I'm looking for.

    Sent from my SM-G973W using Tapatalk

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    Mine is 120 gallons and I use a 5Hp motor with a 7.5Hp VFD.

    The tank came from a air compressor business that put a 5Hp single phase motor on it. But it probably had a 10 or 15 Hp motor on it originally.
    The shop man said that it would work fine. I recently made the conversion from single phase and balanced the 5Hp motor. No need for more Hp.
    I have enough CFM for paint guns and bead blasting.

    Probably if you have multiple people running air tools in a tire change business then a 15Hp would be better. Yuck, the smell from the ChiCom rubber.

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    Quote Originally Posted by rons View Post
    Mine is 120 gallons and I use a 5Hp motor with a 7.5Hp VFD.

    The tank came from a air compressor business that put a 5Hp single phase motor on it. But it probably had a 10 or 15 Hp motor on it originally.
    The shop man said that it would work fine. I recently made the conversion from single phase and balanced the 5Hp motor. No need for more Hp.
    I have enough CFM for paint guns and bead blasting.

    Probably if you have multiple people running air tools in a tire change business then a 15Hp would be better. Yuck, the smell from the ChiCom rubber.
    Yep that may work. I've checked the cfm requirements for the cabinet and outdoor gun we're wanting to use, and they're right at 40CFM full load, hence why the bigger drive.

    I should clarify, we're not blasting engine parts. We're also planning on stripping/repainting a D5H dozer and a Bobcat Skidsteer at some point. The more CFM the better with stuff that big.


    Sent from my SM-G973W using Tapatalk

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    I used a air flow gauge to measure my through my paint gun(s).

    dsc_0609.jpg

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    Agree, that a name brand 30 Hp VFDs may run you around $2500-$2800, then add a DC choke, enclosure, fusing, power switch/contactor and you may be pushing close to $3500 when all is said and done. You will need to size the input end of the VFD for the full 30Hp, so will cost a bit more. Not a big deal to switch the compressor over to run on a VFD, and most compressor pumps specify an operating RPM range for the compressor so slowing it down a bit should work.

    I use mostly Hitachi and Yaskawa units, but a number of VFD dealers seem to be pushing the Fuji Drives which may run a bit less, several models to choose from (see some links below). Teco also has some newer models like E510, installed a few with no problems. They also have the EQ7 model (EQ7-2030-C). You do not need anything with a lot of bells and whistles for what you want to do.
    FRN0115E2S-2GB | Fuji Electric | AC Drives
    FRN030G1S-2U | Fuji Electric | AC Drives
    E510-225-H3-U | Teco Westinghouse | AC Drives
    EQ7-2030-C | Teco Westinghouse | AC Drives

    I have made some VFD control systems for Canadian customers, and seemed to be much more costly to do the installs and get all the approvals for insurance purposes. Since you have electricians on staff and probably access to used electrical cabinets, etc. then you might save a bit on putting it all together. I run derated VFD's in both my mill and lathe, they are designed to be able to run on either single or 3 phase, but the installs were not inexpensive and have a number of hours in each build.

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    Quote Originally Posted by mksj View Post
    Agree, that a name brand 30 Hp VFDs may run you around $2500-$2800, then add a DC choke, enclosure, fusing, power switch/contactor and you may be pushing close to $3500 when all is said and done. You will need to size the input end of the VFD for the full 30Hp, so will cost a bit more. Not a big deal to switch the compressor over to run on a VFD, and most compressor pumps specify an operating RPM range for the compressor so slowing it down a bit should work.

    I use mostly Hitachi and Yaskawa units, but a number of VFD dealers seem to be pushing the Fuji Drives which may run a bit less, several models to choose from (see some links below). Teco also has some newer models like E510, installed a few with no problems. They also have the EQ7 model (EQ7-2030-C). You do not need anything with a lot of bells and whistles for what you want to do.
    FRN0115E2S-2GB | Fuji Electric | AC Drives
    FRN030G1S-2U | Fuji Electric | AC Drives
    E510-225-H3-U | Teco Westinghouse | AC Drives
    EQ7-2030-C | Teco Westinghouse | AC Drives

    I have made some VFD control systems for Canadian customers, and seemed to be much more costly to do the installs and get all the approvals for insurance purposes. Since you have electricians on staff and probably access to used electrical cabinets, etc. then you might save a bit on putting it all together. I run derated VFD's in both my mill and lathe, they are designed to be able to run on either single or 3 phase, but the installs were not inexpensive and have a number of hours in each build.
    Thanks for the reply. Pricing it out it appears we'd be right at 3800 for a 30HP VFD and the necessary chokes etc.

    I happened to be searching for used Phase Perfects and came across a 20HP DPC20 from another member (Nerv on here). I'm going to call Phase in the morning and see if they have any known concerns with the DPC20 line, and ensure that it is worth purchasing. We'll see what happens from there.


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