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Discussion Starter · #1 ·
Looking for the cheapest solition that I can plug into a single phase source (120V or 240V) that will spin a 3 phase motor (various models) up, at variable speeds.

I don't want the full power from a proper-sized inverter, but to bench test motors, adapters, pumps, etc. for eventual EV project integration.

I also don't want to spend time on it - ideally plug n play and ideally is self sensing vs needing resolver hookup.

A kilowatt or two in size is fine as there's not much loading. Variable voltage max would be good. Couple hundred volts would be nice.

Ideas?
 

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Discussion Starter · #3 ·
Not odd...it's for bench testing. Few of us have 3 phase industrial power in the basement/garage.

Was thinking someone might be onto something else besides a vfd.

I don't mind bolting/connecting a board to like a Prius or other hybrid's inverter, but it can't be a project in itself where I spend more than, say 4-5 hours on it and it can't be more than, say $500-$700 total
 

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Not odd...it's for bench testing. Few of us have 3 phase industrial power in the basement/garage.
I mean odd, only in that it is for a 3-phase motor on single-phase power. While that is a logical consequence of running industrial equipment in a residential setting (I know a guy who has a single-phase to 3-phase converter in order to run a lathe, so I realize this does happen), it's not common because industrial equipment is normally used in industrial settings (so normal VFDs with 3-phase output have 3-phase input) and most equipment is designed to be used with the power which is available (so very small industrial and commercial equipment may use single-phase motors on single-phase power sources). Search for "3-phase" motor controllers (VFDs) and mostly you'll find them with 3-phase input.

Was thinking someone might be onto something else besides a vfd.

I don't mind bolting/connecting a board to like a Prius or other hybrid's inverter, but it can't be a project in itself where I spend more than, say 4-5 hours on it and it can't be more than, say $500-$700 total
Of course you can do that, but you need to front it with a substantial AC to DC power supply. It's easy to run past that budget when buying two devices, especially when constrained on the inverter by the (understandable) requirement for sensorless operation.

You can make the power supply side easier to find and set up (and brief testing at higher power possible) by running a common AC-input charger to a small EV battery to power the inverter.
 

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I mean odd, only in that it is for a 3-phase motor on single-phase power. While that is a logical consequence of running industrial equipment in a residential setting (I know a guy who has a single-phase to 3-phase converter in order to run a lathe, so I realize this does happen), it's not common because industrial equipment is normally used in industrial settings (so normal VFDs with 3-phase output have 3-phase input) and most equipment is designed to be used with the power which is available (so very small industrial and commercial equipment may use single-phase motors on single-phase power sources). Search for "3-phase" motor controllers (VFDs) and mostly you'll find them with 3-phase input.
Curious, do you need to debate every philosophical post ? :) Here is a picture of a machine I helped a friend to bring online recently... Sky Motor vehicle Gas Engineering Machine
Circuit component Control panel Electricity Electronic engineering Audio equipment

Two 3-phase motors, two VFDs for conversion from single phase. I also have a 3-phase motor with a VFD in my milling machine specifically to control RPMs, which is a very common pattern for machining equipment.

And yes, these converters have 3-phase inputs which... can also be used as single phase inputs for the phase conversion.
 

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Discussion Starter · #6 ·
...derated for output power when you run single phase into them (you know this, but for the benefit of those reading the thread...there's no free lunch in a VFD phase converter).

After thinking about it, I likely will bench run my motors as a (1ph motor)+(3ph pm motor...as an alternator) ->cables-> (3ph pm motor system under test). Got lots of pm motors, so just need a coupler and to strap 'em down.
 

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It's not derated. If you have a 5HP motor, you will get 5HP output to it from a 5HP rated (or bigger) VFD at the cost of current draw on input. On the other hand I have no idea what would happen when you supply a synchronous motor with power from a VFD intended for use with an asynchronous motor.
 

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After thinking about it, I likely will bench run my motors as a (1ph motor)+(3ph pm motor...as an alternator) ->cables-> (3ph pm motor system under test). Got lots of pm motors, so just need a coupler and to strap 'em down.
Mechanical conversion... a well-established method, and still makes sense since you have the hardware anyway. :) But there's no speed control in there, so it's not really workable at anything other than the shaft speed corresponding to 60 Hz (which might be okay for this purpose).
 

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There's no philosophy being discussed here - just the reality of available products.
These are the units pictured above:
they accept single or 3-phase input.

I used this unit for the milling machine:
 

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These are the units pictured above:
they accept single or 3-phase input.
I see that you carefully edited out the rest of that post of mine when you quoted it:
There's no philosophy being discussed here - just the reality of available products.
Yes, you can buy VFDs with single-phase input and three-phase output, as I mentioned earlier.
... but thanks for the example of what I said was available. ;)
 

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What reality were you concerned with then ?
You should try reading posts before responding to them. All I said, way back when this started, was
So you want a sensorless VFD (variable frequency drive), with the only odd requirement being a single-phase input and 3-phase output... so if you search the web for "2 hp vfd single phase input 3 phase output", you'll find some possibilities...​
No "concern" - just a note to look for the right input power spec. (y)

Note how I quoted your entire post this time, so there is no room for conspiracy theories :p
A conspiracy involves multiple people; in my partial-quote comment I was only referring to one person taking my earlier post without appropriate context.
 

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how about a used water well vfd? I knew a well servicer that had many cheap to buy units sitting in his warehouse collecting dust that were too good to scrap but essentially worthless to customers.
 

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Discussion Starter · #15 ·
All 3 phase VFD's can run on single phase if you're willing to take a hit on your motor power. There are thousands of machines in the wild doing this, with even more running phase converters (which also take an efficiency hit).

Farms are commmercial, not residential, yet many only have single phase power available.

If you have two devices, you're not buyng anything.

Pay attention and thanks for all your Google research.
 

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I don't believe there is loss of power on output. If the VFD is rated to the same power as the motor in question, there should be no penalty. I've installed several VFDs so far ranging from 2kW to 10kW, and their specs made it obvious that they will be drawing a lot more current from a single phase input than will be going to the motor at its rated max. There are several classes of devices that allow for running 3 phase equipment from a single (or split) phase, maybe that's where some of the confusion is - rotary phase converters, inverter style VFDs, static phase shifters, etc.
 

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Discussion Starter · #17 ·
You lose power because the front end filter caps are not sized large enough to provide power over a cycle that zero crosses at 120 Hz...rectified 3 phase has very little ripple. My machine is 10HP in 3 phase and I seem to recall it degrades to 7HP on one phi.
 

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You guys are hilarious. The "robinkyle11" bot reposted some old content from post #4 of this thread, and you guys are acting like there's actually a conversation going on. :D
But sure, if you want to re-start a conversation that you already had, go for it.
 

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I am pretty distracted with a bunch of stuff happening at the same time (stressful), so I jump on these discussions as a way to get away from the other nonsense. Yeah, need to pay better attention.
 
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