vfd question

[Chris A Lawrence]

So i have been kicking around this 3 phase 2 hp dust collector that came with a unisaw i purchased awhile back. I am looking at getting a vfd off ebay for it to make use of it. I know i need to get a larger vfd when going from single phase to 3 phase. Would a 3 hp vfd be enough or do i need a larger one?

[Mike Heidrick]

You need a vfd rated for the hp motor you are driving, at the input voltage you require, that will deliver the fla required by the 3ph motor. You do not need to oversize if the vfd is rated at 230v 1phase input.

[John Lifer]

Yep, look for old single phase input rated at your needed amps output. I use a couple of brands I've sourced successfully off eBay. I avoid teco had poor luck with them

[Mike Heidrick]

Inrun hitachi wj200, x200, teco fm50, teco 7500, fuji mini 300, and a Benfigilio (sp) ip65 nema 4. Used to have a Hitachi 1hp that ran off 120v. They have all been excellent. The Hitachis are my favorite but 2x the cost of ebay ones at least. For my cnc machines I like the rs485 comm, dc braking, and the ability to run a remote readout all at the same time on the wj200. Excellent.

[Peter Christensen]

I suggest you contact Powtran (http://www.powtran.com/en/) in China (click the British flag if it comes up in Chinese) through their service tab and tell them what your motor data plate says. They will tell you what would work and what the cost with shipping will be. You can also find them on Alibaba if you prefer. Many VDF's on eBay are Chinese anyway. It is the brand Clear-Vue in Australia use to bring their 50 cycle current to North American 60 cycle on their machines.

[Chris A Lawrence]

ok so i got a vfd off of ebay it powers the motor but i am only getting around 200 cfm's out of it. I have it set for 60hz per the motor specs any thoughts whats going on? Its wired up for its low voltage configuration. I am powering the vfd with 220 single phase.

[Tom M King]

Check to see if it's rotating in the correct direction. A simple try would be to hit the reverse button (edited to add: before the start button), and see if you get better suction. I don't really know if one would provide any suction at all with the impeller rotating the wrong way, but it would certainly be a lot less than the correct direction.

[Chris A Lawrence]

That had no change still feels the same. Do the wires from the vfd need to be connected to specific leads on the motor? The tag has diagrams on how to wire it for low and high voltage but dont give any labeling for specific wires like on the vfd.

[Tom M King]

PM the seller on ebay with a picture of the motor plate on the motor. If it's the same one I've bought a couple from, he'll get right back to you with exactly how to wire it.

[Bill Dufour]

should be three input leads on the motor. hook in any order to the vfd output terminals. Also a ground lead. vary the frequency a bit and see if rpm changes or not.
What voltage was the saw wired for? is it also three phase?
Bil lD

[Chris A Lawrence]

its not a saw its a blower. It had a sticker on it that said 208v and the wire connections in the junction box are in the low voltage configuration. It is a 3 phase 2hp motor and the vfd is a 1 phase / 3 phase 2 hp vfd. The cfm's go up a few if i lower it to 56 hz but that seems to be the sweet spot.

[Chris A Lawrence]

so a new development. The motor had 8 foot tails for all the hot legs but the ground was cut inside the junction box. I didnt have wire but just got some tonight to make the ground connection. When i connect the ground for the motor to the ground lug in the vfd it trips the breaker. Unless your not supposed to tie the motor ground with the ground from the sub panel i think there might be a problem in the motor. The motor is way used i have a few places near me that work on electric motors i am going to call around and see if its worth them looking at and possibly fixing.

[Bill Dufour]

Sounds like one of the winding is is shorted to ground. use a meter and measure each coil to ground. They should all be infinite resistance. Also measure each coil end to end and to the others. End to end under 5 ohms. One to another will vary by wiring type but they should all three be equal.
Bill D

[Chris A Lawrence]

so all the ohms tested out ok. Another question what should the voltage be for each leg when tested to ground. what should it be when tested across 2 legs. When i test the voltage from my vfd across the ground 2 legs get 180 and one was 178. when i measured across 2 legs i was getting 280 and my meter was maxing out. Is this normal?

[Chris A Lawrence]

Thanks for all the sugestions everyone. I need to learn to read manuals better. I missed a setting on the vfd and it fixed it. It blows like a hurricane now.

[Bill Dufour]

Please tell us what setting was off so future searches can learn in the years to come.
Bill

[Chris A Lawrence]

i missed the frequency setting for the motor. The vfd had a couple settings for frequency i missed one and the default was 400 Hz.

[Bill Dufour]

I have only heard of 400Hz being used in aircraft stuff. My VFD has a 400HZ setting as well but being from China it was set for 50Hz from the factory.
Bill

[Chris A Lawrence]

well this one was from china and all the default Hz settings where for the max setting of 400 Hz. Just glad i didn't mess up the motor. Granted it wouldnt have cost me any money other then the cost of the vfd as i got the blower included with my $200 unisaw. I would of had to just deal with my 1hp harbor freight dc for awhile longer.

[Mike Heidrick]

I have only heard of 400Hz being used in aircraft stuff. My VFD has a 400HZ setting as well but being from China it was set for 50Hz from the factory.
Bill

Almost all CNC router spindle 4 pole motors use 400Hz for 24000rpm.