Can all VFDs convert single phase to 3 phase?

[Jraef]

If you like watching paint dry, I have a youtube video where I reform the caps in a VFD using the variac method

The VFD will most likely turn on around 60% rated voltage with an undervoltage error.

I've found most VFD's will run on single phase, even higher (600v) ones, as JST said you may need to set a parameter to ignore the input phase fault.

The fault is irrelevant in this case, you are not wanting to run the motor while reforming. You are still reforming the caps even if the drive is faulted.

 

[brunswick1901]

I have a 240 volt 10hp 3 phase air compressor that I’m trying to run using a VFD. I only have 240 volt single phase service.

I have found a used VFD locally that is made for 30 hp motors. The make/model is ABB ACS401603022. I read through the manual and in the wiring guide it states that the input power supply should be 3 phase with a note: “Do not use in 1~ supply!”

I’m taking this to mean that it can only use 3 phase power input and not single phase.

I was under the impression that all VFDs could convert single phase to 3 phase, and you simply derate the VFD by half if you are using a single phase input.

Am I wrong?

Is your air compressor reciprocal piston compressor driven with v-belts? If it is it is probably cheaper to change the three phase motor to a single phase motor.

If you do not mind the tank taking a little longer to fill up a single phase 7.5hp motor will be much cheaper than a 10hp motor single phase motor.

 

[greenbuggy]

running 30 hp will take about 150A of that 200A service...

OP says they want to use it to run a 10 HP load, a 30 HP VFD isn't going to use 30 HP worth of electricity to run a 10 HP load.

I've done what OP wants to do to run a 7.5 HP CP Quiet Rotary Screw (QRS) compressor, using a 240V 30 HP Teco drive. Total overkill for what I'm using it for but I bought the drive with a blown output stage and fixed it for <$150.

To answer OP, nearly all drives can take and rectify single or 3 phase input power to feed their DC bus and cap bank, but not all drives have the ability to turn off an input phase loss error when it occurs, and nearly all drives will refuse to do anything once that error code is set.

Derate is usually used to give ample safety factor to avoid blowing out your input rectification or getting anything too hot, but the way many drives spot an input phase loss is by seeing an excessive amount of ripple on the DC bus voltage because there's only 2 AC legs and not 3 getting rectified into DC power

 

[brunswick1901]

It has been experience that running a compressor with a VFD or a rotary phase converter, RPC, is not recommended because a compressor will need a of amps to start the three phase motor in the compressor. My experience is only with RPC and everyone that builds RPCs will recommend a RPC that is three times the horsepower of the motor in the compressor.

A 10hp compressor will need a 30hp a RPC. A 30hp RPC will need a 60 amp breaker to start but once the idler motor is running the RPC will draw 16 to 20 amps. After you start your 10hp compressor it should draw less than 20 amps.

When both the RPC and your compressor are running you should draw a little less than 40 amps.

The RPC will also have the advantage that you will be able to run other three phase motors as long as you use the correct wire and breaker size.

I have been told that most VFDs will eventually fail, another advantage of a RPC is a well built RPC can run for many years without any problems.

Please message me if you have any other questions.

 

[greenbuggy]

I have been told that most VFDs will eventually fail, another advantage of a RPC is a well built RPC can run for many years without any problems.

I'm not sure who told you that but if they're implying that a VFD will fail because of the limited lifespan of the electrolytics, I have some real bad news for you about the start and run caps in your RPC

 

[brunswick1901]

I agree with you that RPC have problems with capacitors and perhaps it is just bad luck greenbuggy VFD failed. I was surprised that his VFD need 150 amps to run his compressor. I measured the amps I mentioned in my first reply and committing 150 of the 200 amps to run the VFD will surely limit what else he needs to run.

Perhahs I should have said based on the amps needed the RPC is the best choice regardless of of its reliability and not mention that VFDs sometimes break.

 

[JST]

A properly designed compressor will not need a lot of amps to start..... The solution to starting against "head" is an unloader, which nearly every compressor will have.

The motor will start against zero head, and is up to speed when the unloader connects it to the tank.

A bigger problem is that compressors may have underrated motors, because the max amperage is at the end of the cycle, where the head is highest. A small overload there is for a short time, only, and the "value engineering" folks will say it won't fail in the warranty time, so go for it.

That's for more "consumer" compressors. Industrial ones are generally no-nonsense.

If you are worried about RPC capacitors, then what about all that oil you need for bearings? Right... rpc start capacitors are consumables, although most decent manufacturers do not use the cheap electrolytic types.

VFD capacitors are not consumables, because users generally cannot replace them, and it's often cheaper to replace the unit and get on with life. Large inverters are worth repair sometimes.

 

[greenbuggy]

perhaps it is just bad luck greenbuggy VFD failed

Someone else caused it damage and I replaced the failed components. Has not had a single issue since I did the work to repair it.

Nobody is suggesting that OP use 150 amps of power to run a 10 HP load, that would be insane. As I said above, a VFD thats rated for 30 HP isn't going to draw 30 HP worth of power to run a 10 amp load. A 10 HP motor at FLA on 230V is about 15 amps give or take (powered using 3 phase), to power the 3 phase load on single phase its nearly double that, about 30 amps on single phase is nowhere near 150 amps.

And this isn't even factoring that most compressor motors are sized for start since the load is highest at startup (using a contactor to start the load) and usually falls off as the compressor reaches running speed.

 

[Strostkovy]

I actually built an unloader for my homemade very quiet compressor. I didn't want to deal with huge power surges, and the pumps I'm using aren't a fan of 208V anyway, so I just used a time delay relay to power a valve that closes the bleedoff connection to the muffler a few seconds after the motor is powered.


You can see the valve at the bottom of the picture. I have since replaced the tiny muffler with a much larger silenced one.

 

[JST]

I have a similar Gast pump, which is a diaphragm type. It works well for free flow blowing chips away during a cut, but is no good for use with a tank, because it will not start against a head.

I got an unloader from McMaster, but even it, at the low flow it was rated for, will not actually "trip-in" when the pump is up to speed.

A timed valve type is a better idea. I may even have a suitable valve around here.