25hp phase converter powering vfd to adjust speed of 3 hp motor for paint booth fan . I’ve burned up 2 vfds in 2 weeks . Got another vfd and called to get it looked at before install again and was told cannot run vfd and phase converter together as it messes with waves of the power. He didn’t have a solution except get true 3 phase power. . What else can I do?
Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
Largest Manufacturing Technology Community on the Web
Stay Connected:
Phase converter running vfd problems
- Thread starter Mikesfd
- Start date
- Replies 13
- Views 1,388
jim rozen
Diamond
- Joined
- Feb 26, 2004
- Location
- peekskill, NY
Do you have the load motor wired directly to the VFD output - no switches or contactors?
He gave rather an "interesting" description of the problem....no clue what he thinks he was saying...
The actual problem may be that the (we presume) Rotary Phase Converter which is lightly loaded, may produce a high output voltage, possibly damaging the VFD. Most VFDs have "balance" capacitors on them to raise the output voltage of the "generated leg" under full load. But when lightly loaded the voltage is not stable, and can go very high. That may not bother a motor, but it can damage a VFD.
You do need to use the VFD to control the fan, and not regular power switches. Some VFDs do not "like" being switched.
Brandenberger
Hot Rolled
- Joined
- Sep 19, 2017
Any reason not to get a VFD with single phase input? Either use a bigger one derated on single phase or one designed for single phase input. And connect before the phase converter of course, not after it.
So the 25hp converter powers a 10hp intake fan and a 3 hp exhaust fan which just the 3hp is connected to the vfd to increase or decrease booth pressure for painting , when the phase converter is turned on the vfd is powered there is not switch in between . I think when the booth is turned on the 3 hp motor starts first then the 10hp after a delay period.
This booth was running on 3 phase at its original location without a phase converter , so the only difference from original is me trying to run it of a 25hp phase converter
This booth was running on 3 phase at its original location without a phase converter , so the only difference from original is me trying to run it of a 25hp phase converter
OK, not lightly loaded. Still could be very high voltage when the fans are not running, but the VFD is powered up, however.
Can you give any details of what was going on when the VFD failed? (right when power applied, while running, etc)
Any voltage measurements of the converter output?
Any description of how the VFD failed? (quietly quit, blew the breaker, filter capacitor exploded, that sort of thing)
Can you give any details of what was going on when the VFD failed? (right when power applied, while running, etc)
Any voltage measurements of the converter output?
Any description of how the VFD failed? (quietly quit, blew the breaker, filter capacitor exploded, that sort of thing)
I’m assuming the vfd fails on startup. Worked one day then flipped the switch to turn on and nothing, the vfd is out back in the outdoor heater unit for the booth, fuses for the vfd before it blow and there’s no fuses after the vfd to the motor .1st vfd started on fire 2nd had a slight smoke smell and only worked 2 days(was reconditioned unit ) Had the voltage measured was about 120 on 1and 3 . 2 was around 200 don’t remember that what the electric co told me and said it was normal.
Overland
Stainless
- Joined
- Nov 19, 2017
- Location
- Greenville, SC
If I'm understanding correctly, you have 2 separate motors.
The 25 hp running off the phase converter and the 3 hp off the VFD.
I'm not understanding why you're connecting the VFD to the phase converter.
Why not run the VFD directly from a separate single phase input ?
Just make sure the VFD output when supplied by single phase is at least the rated current of your motor (or get a VFD with twice the hp rating).
I have several VFD's running on single phase input to power 3 phase machine - very simple and reliable.
Bob
The 25 hp running off the phase converter and the 3 hp off the VFD.
I'm not understanding why you're connecting the VFD to the phase converter.
Why not run the VFD directly from a separate single phase input ?
Just make sure the VFD output when supplied by single phase is at least the rated current of your motor (or get a VFD with twice the hp rating).
I have several VFD's running on single phase input to power 3 phase machine - very simple and reliable.
Bob
Rob F.
Diamond
- Joined
- Aug 5, 2012
- Location
- California, Central Coast
No, he has this:
If you are only using the 3hp motor on the VFD it would make sense to get a VFD to covert from single phase to run that motor. That would eliminate any RPC caused voltage problems. read the ratings for the VFD carefully, many in that size and smaller are able to do single phase in and 3 phase out.
The unit was set up with 3 phase incoming and in the box was split to the 10hp motor and then split to the vfd to the 3hp , this was the original setup from Voc systems ( the booth manufacturer ) . I assumed all I need was a phase converter to run 3 phase to the box and I would be good to go. But now after blowing 2 vfds and asking around I’m hearing I can not run 3 phase converter and vfd .
Im think this is my best bet , it first I was thinking I was going to have to buy a 3hp single motor and a vfd to adjust it but now knowing you can get a single phase to 3 phase vfd that sounds like the best way to go .
Overland
Stainless
- Joined
- Nov 19, 2017
- Location
- Greenville, SC
This is Fuji document on using VFD with single phase input:
https://www.wolfautomation.com/medi...n/fuji-frenicmini-c2-feca-an-175-appnotes.pdf
fuji would recommend: C2S 0020 2U
This is available from Marshall Wolfe: In Stock !!
FRN0020C2S-2U | Fuji Electric |
I have 5 of these VFD's of different power levels, up to a 15 hp lathe.
Had great success with these, and they're very reliable.
Good luck,
Bob
https://www.wolfautomation.com/medi...n/fuji-frenicmini-c2-feca-an-175-appnotes.pdf
fuji would recommend: C2S 0020 2U
This is available from Marshall Wolfe: In Stock !!
FRN0020C2S-2U | Fuji Electric |
I have 5 of these VFD's of different power levels, up to a 15 hp lathe.
Had great success with these, and they're very reliable.
Good luck,
Bob
This system is running on "farm/lighting tap/stinger" 240V. That, and also "corner grounded" 240V have a higher peak voltage to ground than "wye" connected 3 phase.
Where that can be important is that if there are voltage spike protectors (MOVs, typically), they can be presented with spikes over their rated voltage with those connections. The MOVs are from line to ground, so they would be selected to work with 139VAC (the wye voltage to ground), and might be very close to operating on every peak with the higher voltage to ground of your connection (around 200VAC).
The "fire" mentioned is pretty typical of that type of failure, where the MOVs are simply over-powered. I've seen it before.
Usually, the instructions say to disconnect the MOVs in that case, if that is possible. With Invertek units, there was a screw that is removed to disconnect, I do not know for other types.
Some have no provision for disconnecting, and are not recommended for usages other than wye type 3 phase. That includes some expensive brands.
