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460v VFD with Single-Phase Input?

squeeze

Plastic
Joined
Jan 20, 2012
Location
Connecticut, USA
I have several VFDs running single-phase 230v to 3-phase 230v ... works like a charm. I have an RPC generating 3-phase 230v, with a transformer to step that up to 440v (multiple taps) ... works like a charm.

It was suggested to me to use a single-phase transformer to step up my voltage from 230v (single-phase_ to 460v (single-phase) and then convert to 3-phase with a VFD. I'm having trouble finding a 460/480volt VFD that takes a single-phase input. The tool I'm looking at is a woodworking jointer of 5 hp. The startup resistance is relatively low. In reality I would only be using the slow start feature of the VFD, but of course the phase conversion also.

The recommended VFD was the GE AF60-LP. Yet when I look at the manual for that or the AF300 series, they indicate 3-phase input only. I used the manual to construct a "part number" but get zero results searching for that configuration. I'm also seeing in the Teco Manual the following ..."***Do Not Apply Single Phase Input Power to these Models" ...

Hoping I'm wrong. I'm a woodworker and maintain machines for that purpose but I have found folks in this forum exceptionally knowledgeable and helpful with respect to these types of questions. I apologize if this question has been answered too many times to count.
 

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You won't find it directly stated, because "single phase" 480V is almost unheard of, so VFD mfrs will not make a "special" version that will not sell.

But that doesn't mean you can't do it. Technically, ANY VFD can be fed with single phase power, but some designs don't ALLOW it because they are afraid of it being misused.

A VFD only uses the incoming AC line power as a resource to make DC. It makes no difference initially if it is coming in on 2 lines or 3 lines. What DOES make a difference is the amount of current passing through the converter, and the "ripple" of the DC bus that feeds the transistors in the "inverter" section.

Current: If you have a 460V 5HP 3ph motor and 5HP is 3.73kW of power. The current that it draws is averaged out over 3 phases, so it is drawing 7.6A per phase. But if you FED the DC bus from a single phase source, it STILL has to draw 3.73kW of power, but must do so from only 2 lines, not 3. So the current going IN to the drive on those 2 lines increases by the square root of 3 (1.732x), therefore the rectifier COMPONENTS in that drive are now going to see 13.16A, yet they were DESIGNED o only have to carry 7.6A.

Ripple: When the rectifier components pass the AC through in only one direction to make DC, the DC is not smooth, it is rippled, because the current was going up and down in the incoming sine wave of AC, but only conducted for parts of each wave. The transistors on the output side don't function well if there is too much ripple, they can misfire and/or over heat. So the VFD has a bank of capacitors inside to smooth out that ripple. The more ripple you have, the more capacitance you need.

So because of these issues, a VFD used on a single phase supply must be at LEAST double the rating of the motor, maybe more. Each mfr will have a de-rate factor that you can apply. If they STATE that the de-rate factor is 50%, you can use that. If they DON'T state that explicitly, the only safe bet is to use a 65% de-rate, or use a 50% de-rate and also de-rate the ambient temperature by 50%. So that means if the drive was rated for 40C (104F) ambient, you can use the 50% de-rate if the maximum ambient is just 20C (68F), which is damned near impossible. The reason for that last issue is because just doubling the capacitor size works to smooth out the ripple, the the capacitors themselves will run hotter and might burn up. The reason some drives say 50% is OK is when they use a DC bus Choke (inductor) to assist the capacitors in smoothing the ripple. Still, lot's of people take their chances with a 50% de-rate even without a DC choke and it's fine, but likely because the duty cycle is low enough that even if they cut the VFD life in half, it's longer than they need anyway.

So in your case, you can buy a 10HP 480V VFD (one with a DC bus choke) and run your 5HP motor with it. The only tricky part is that not ALL 10HP 480V drives will allow you to do this. That's because they build in an "input phase loss" detection system that is meant to protect the drive IF you have 3 phase and a fuse blows, so that the normally rated drive is not damaged. If you select a drive that has that feature, you have to look in the programming manual to see if you can disable it. If not, you CANNOT use that drive. If you can disable it, then it's no problem.
 
J is right but overbroad..

Smaller VFD's may accept single phase in, as you are aware. They have input circuitry designed to handle the larger current and ripple. At lower power levels, this does not add much cost to the design.

At 440 v level, Jreaf's points become much more important.

SOME drives with phase loss detection, can be fooled into operation.. I will let you research that..

And as I alway pop in, there are VFD's out there designed from factory, to accept 220v single phase input only... Up to 50 hp.

440 v does make things tough, for single phase fed shops. I try to only buy equipment with dual voltage 220/440 motors..
 
I'd even say "most" 230V new VFDs under 5hp are single phase compatible directly at full power.

Quite a few are available that will double 120 V to give 3 phase out at 1 hp and below.

When you get to 5HP and 460V. your choices are much more limited.
 
Mitsubishi for one will endorse certain of their freqrol inverters for use with only 2 of the 3 phases. In that case you have to derate the inverter so you don't overload the bridge rectifier. In the UK our mitubishi dealer had some sort of table to indicate which larger inverter was needed. Phase loss is usually turned off by default in those inverters.

Another option is a seller on ebay I've seen who supplies Teco 3-phase 220/240V single phase inverters modified to give out 415V 3phase. It's done by employing an internal DC voltage capacitor-doubler circuit.
 
I'm having trouble finding a 460/480volt VFD that takes a single-phase input.


Most will, provided they don't have phase-loss protection, or if they DO, it's 'smart' enough to not be fooled by a small capacitor connected between one of the hot legs and the unused input.

But the Allen Bradley 1305, 1336F and 1336S drives will all run happily on single phase 480. Most will agree that they're old and obsolete, with cheezy plastic exterior, but plentiful, inexpensive to obtain, and work well.
 
Most will, provided they don't have phase-loss protection, or if they DO, it's 'smart' enough to not be fooled by a small capacitor connected between one of the hot legs and the unused input.

But the Allen Bradley 1305, 1336F and 1336S drives will all run happily on single phase 480. Most will agree that they're old and obsolete, with cheezy plastic exterior, but plentiful, inexpensive to obtain, and work well.
It just needs to be noted that they are all long obsolete (last sold in 1998) and no longer supported by AB, so there are no replacement parts available other than FleaBay or other used parts sources. AB has had programs in the past that gave credit to users who upgraded with the proviso that the units taken out of service be destroyed. But people rescue them from recycle bins and sell them on FleaBay. Many of them have been purposely hobbled or ruined as a result, but the FleaBay resellers don't know that or don't care. I still get probably 3-4 calls per month from people having bought them and are angry that they don't work and not supported by the factory, then when they send them to 3rd party repair houses, end up spending more than a new drive would have cost them. That's not to say they are all bad, just know up front it's a buyer beware situation.
 
hi i am just leaning bout electrical stuff. what is vfd? i am very much interested in motor an their controls
 








 
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