VFD on a salvaged HVAC motor?

I'm the recipient of an EC motor from an HVAC system that was removed as "defective". I know it runs, since supplying 120 VAC to the power terminals and 24V AC to the control terminal makes it run, unfortunately in the wrong direction to drive my South Bend Light Ten lathe. The control connections are completely obscure, apart from the one pin that runs the motor when it sees 24V..

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The general info I found on EC motors suggest they may be internally reversible. Does it have an identifying nameplate you could look up?

You lost me. A 3 phase motor will typically not start and run if you hit it with single phase power. To my knowledge 110V AC is not generally supplied as 3 phase.***

It is possible sometimes to get a 3 phase motor to run on 3phase by giving it a spin while powered up on two legs, by using a cap to the other leg, or using a phase converter of some kind which does include a VFD as one option.

I've never played with it, but I've been told repeatedly that running a single phase motor on a VFD is a recipe for bad juju.

That being said if you actually have a 3 phase motor its dead easy to make it run in either direction. Hook it to three phase power, and if it runs in the wrong direction swap any two of the three legs. If using it with a VFD do it in a state where the motor is not being powered. Switching the output of a VFD while it is putting out power is a well known recipe for bad juju. Usually blows the VFD. Not in a good way.

If using a VFD with a good 3 phase motor, the VFD can be used to reverse the motor. No need to mess with any sort of switching other than on the inputs of the VFD. NO SWITCHING ON THE OUTPUTS.

*** I also have a 11OV in VFD that puts out 220V 3 phase for small spindles. Its current driving an 800W spindle on the machine I only use for engraving.

*** The motor inside the pump is probably the only one big enough to be suitable to drive a lathe. I guess some huge air handler might have a big motor on the squirrel cage, but if its an inverter controlled motor it likely cheats its way to peak HP by careful ramping.

*** Most 3 phase motors are capable of running from about 1/2 speed to about double speed, but a really cheap motor may have questionable bearings at high rpm and cooling capability at low rpm. The addition on a secondary cooling fan motor may help with the latter. My Leland spindle motor on my Hucro KMB1 has a separate cooling fan motor inside the motor case. Of course looking for an "inverter duty" motor may help.

I know it can sound like a lot of complicated malarkey, but its really not to bad. Knowing what values to program in the VFD can be a little tricky, but you can figure it out.

*** If you waded through my run-a-way diatribe and still want to proceed remember that most VFDs need to be derated by about 1/3 when used as a phase converter.

You lost me. A 3 phase motor will typically not start and run if you hit it with single phase power. To my knowledge 110V AC is not generally supplied as 3 phase.***

It is possible sometimes to get a 3 phase motor to run on 3phase by giving it a spin while powered up on two legs, by using a cap to the other leg, or using a phase converter of some kind which does include a VFD as one option.

I've never played with it, but I've been told repeatedly that running a single phase motor on a VFD is a recipe for bad juju.

That being said if you actually have a 3 phase motor its dead easy to make it run in either direction. Hook it to three phase power, and if it runs in the wrong direction swap any two of the three legs. If using it with a VFD do it in a state where the motor is not being powered. Switching the output of a VFD while it is putting out power is a well known recipe for bad juju. Usually blows the VFD. Not in a good way.

If using a VFD with a good 3 phase motor, the VFD can be used to reverse the motor. No need to mess with any sort of switching other than on the inputs of the VFD. NO SWITCHING ON THE OUTPUTS.

*** I also have a 11OV in VFD that puts out 220V 3 phase for small spindles. Its current driving an 800W spindle on the machine I only use for engraving.

*** The motor inside the pump is probably the only one big enough to be suitable to drive a lathe. I guess some huge air handler might have a big motor on the squirrel cage, but if its an inverter controlled motor it likely cheats its way to peak HP by careful ramping.

*** Most 3 phase motors are capable of running from about 1/2 speed to about double speed, but a really cheap motor may have questionable bearings at high rpm and cooling capability at low rpm. The addition on a secondary cooling fan motor may help with the latter. My Leland spindle motor on my Hucro KMB1 has a separate cooling fan motor inside the motor case. Of course looking for an "inverter duty" motor may help.

I know it can sound like a lot of complicated malarkey, but its really not to bad. Knowing what values to program in the VFD can be a little tricky, but you can figure it out.

*** If you waded through my run-a-way diatribe and still want to proceed remember that most VFDs need to be derated by about 1/3 when used as a phase converter.

I'm the recipient of an EC motor from an HVAC system that was removed as "defective". I know it runs, since supplying 120 VAC to the power terminals and 24V AC to the control terminal makes it run, unfortunately in the wrong direction to drive my South Bend Light Ten lathe. The control connections are completely obscure, apart from the one pin that runs the motor when it sees 24V..

There are lots of packaged VFDs on Amazon, some for less than $100, that accept single phase 120v input and are said to drive "most" 3 phase motors within their size range, typically 1-3 kW. This motor is a Genteq ECM 3.0, I see only the three power wires going from control to motor, no tach or feedback connections. It's rated at half horsepower, with no electrical specs on the tag. Turned by hand, it does not seem to cog, so I don't think it's a PM motor.

Does anybody have experince or ideas about this notion?

Thanks for reading, and any ideas!

bob prohaska

-------------------------------------- I replaced the 220V 3Ph motor that came on my South Bend 10L with a TEFC

I think that's true, but the "identifying nameplate" isn's much help. It specifies "ECM 3.0" and nothing else. I believe that implies a digital interface of some sort but I've had no luck learning more. I was able to glean the go/no-go test using 24VAC and that's it.

A generic 3 phase VFD looks superficially like the simplest approach.

Thanks for writing,

bob prohaska

Jim Wilkins snipped-for-privacy@gmail.com wrote:>

I think that's true, but the "identifying nameplate" isn's much help. It specifies "ECM 3.0" and nothing else. I believe that implies a digital interface of some sort but I've had no luck learning more. I was able to glean the go/no-go test using 24VAC and that's it.

A generic 3 phase VFD looks superficially like the simplest approach.

Thanks for writing,

bob prohaska

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If it rectifies the incoming AC to DC for an inverter the line frequency will have little or no effect, though reduced voltage might.

After reading Jim's description a VFD would be of no use to you at all. I might try a variable power supply on the input. 0-10 and 0-5 vdc are common input signal voltages for motor controllers. I don't see any reason why it couldn't be 0-24. On the motor controllers I am most familiar with the signal voltage is usually DC, but AC is much easier to derive from an AC source like wall power.

I wonder if its signal voltage for control, and pulse width modulation for speed. Pulse width modulation has been in commercial use for retail products for 50 years that I am aware of. At anything under 100% on its supposed to be a huge power saver over other methods of speed controlling a motor. Minn Kota sold it as an add on for 12V electric trolling motors 50ish years ago. I used a pulse width modulation control on a universal motor on a lathe maybe 10 years ago.

I'm not up much on brushless DC motors. Universal DC motors don't have much power/torque at low RPM, but the pulse width modulation control was much better than a voltage level control.

Just for the heck of it I did a search for an EC 3.0 motor. The AI result seems realistic to me.

ECM 3.0 Blower Motor Specs Horsepower (HP): \(\frac{1}{3}\) to \(1\) HPRPM Range: \(200\) to \(1,800\) RPM (multi-speed/fully modulating) Voltage: 115V or 208-230V Phase: Single phase Enclosure: OAO (Open Air Over) Frame Size: 48Y Mounting: Belly band Shaft Size: \(\frac{1}{2}\) inch diameter Controls: 9-pin or 16-pin integrated moduleThese constant-torque or constant-airflow brushless DC motors are designed to optimize energy efficiency in HVAC air handlers and furnaces

After reading Jim's description a VFD would be of no use to you at all. I might try a variable power supply on the input. 0-10 and 0-5 vdc are common input signal voltages for motor controllers. I don't see any reason why it couldn't be 0-24. On the motor controllers I am most familiar with the signal voltage is usually DC, but AC is much easier to derive from an AC source like wall power.

I wonder if its signal voltage for control, and pulse width modulation for speed. Pulse width modulation has been in commercial use for retail products for 50 years that I am aware of. At anything under 100% on its supposed to be a huge power saver over other methods of speed controlling a motor. Minn Kota sold it as an add on for 12V electric trolling motors 50ish years ago. I used a pulse width modulation control on a universal motor on a lathe maybe 10 years ago.

I'm not up much on brushless DC motors. Universal DC motors don't have much power/torque at low RPM, but the pulse width modulation control was much better than a voltage level control.

If this turns out to be the case a power supply and a potentiometer would make a fair manual speed control. Lots of stuff is or can be controlled that way.

If this turns out to be the case a power supply and a potentiometer would make a fair manual speed control. Lots of stuff is or can be controlled that way.

Perhaps I posed my question in the wrong way. The ECM motor is basically a 3-phase motor with its own VFD, which I can't figure out how to test extensively or use.

The idea was to discard the ECM 3.0 assembly entirely and replace it with a standalone cheap VFD. The ECM 3.0 unit was declared "bad" by the service tech; the fact that the motor runs in test mode suggests the motor, at least, is OK. If the controller is inscrutable just toss it and buy a cheap VFD.

Is it sufficient to find a VFD with the right power and voltage ratio, or do I have to match more detailed specification? All I know about the motor is that it uses 120 volts, is rated at half a horsepower and runs at around 1000-2000 rpm.

That's the experiment I was asking about, not how to re-use the entire unit intact.

Thanks for reading, and all the replies!

bob prohaska

Perhaps I posed my question in the wrong way. The ECM motor is basically a 3-phase motor with its own VFD, which I can't figure out how to test extensively or use.

The idea was to discard the ECM 3.0 assembly entirely and replace it with a standalone cheap VFD. The ECM 3.0 unit was declared "bad" by the service tech; the fact that the motor runs in test mode suggests the motor, at least, is OK. If the controller is inscrutable just toss it and buy a cheap VFD.

Is it sufficient to find a VFD with the right power and voltage ratio, or do I have to match more detailed specification? All I know about the motor is that it uses 120 volts, is rated at half a horsepower and runs at around 1000-2000 rpm.

That's the experiment I was asking about, not how to re-use the entire unit intact.

Thanks for reading, and all the replies!

bob prohaska

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My only experiment with a regular 3 phase motor was using a 20uF motor run capacitor in series with the third phase. A Variac with an ammeter showed that the current wasn't excessive as I raised the voltage until it turned.

Before powering the motor I tested from the windings to the frame with a Megger to see if it had been rejected for excessive leakage. I've bought a few used items that failed that test until cleaned.

I used a PWM unit to build a temp control for my motorcycle gloves . Got another unit in a box out in my shop that needs a project . Also got a DC/PM treadmill motor that needs a project , but I don't think this PWM unit will handle that load .

Perhaps I posed my question in the wrong way. The ECM motor is basically a 3-phase motor with its own VFD, which I can't figure out how to test extensively or use.

The idea was to discard the ECM 3.0 assembly entirely and replace it with a standalone cheap VFD. The ECM 3.0 unit was declared "bad" by the service tech; the fact that the motor runs in test mode suggests the motor, at least, is OK. If the controller is inscrutable just toss it and buy a cheap VFD.

Is it sufficient to find a VFD with the right power and voltage ratio, or do I have to match more detailed specification? All I know about the motor is that it uses 120 volts, is rated at half a horsepower and runs at around 1000-2000 rpm.

That's the experiment I was asking about, not how to re-use the entire unit intact.

Thanks for reading, and all the replies!

bob prohaska

---------------------------

After reading Jim's information and doing a little lookup of my own the motor at its core (just the motor) is likely a DC 3 phase motor. A conventional off the shelf VFD would be completely useless as they put out variable frequency AC or at most/worst offset symmetrical square wave variable frequency AC.

Cutting into the VFD and taking the output off the converter would kind of make the whole exercise moot. I hesitated to mention that as a possibility as it seems counter productive when (next paragraph).

What you need to look for I think is a 3 phase DC motor controller that uses pulse width modulation for speed control. There are a lot of them out there, and they aren't particularly expensive. Much cheaper than a VFD. Many of them can take variable signal voltage or a POT for speed control. Those that just use a POT generate their own signal voltage and use the pot as a signal divider. That exact application may be transparent to the user.

The issue will be voltage and current. While the input to the packaged controller seems to be 110VAC the output to the motor windings can be anything DC. You can work backwards to a limited extent, knowing its probably 1/2 HP (about 400 watts output) you can just use some form of (amps times volts = watts) to figure out a likely controller that shouldn't blow up as soon as you power it up. Its very likely not at the high end of the voltage spectrum since a buck boost transformer would add to the cost, but with very limited electronics it could be from any lowish voltage upto to 160VDC. 160VDC is the approximate result of straight bridge rectified 110V AC. A simple voltage regulator could drop that after the regulator or a simple transformer could drop that before the rectifier. You can likely look at the existing controller and figure some of this out. I would go with a nominal minimum 750-1000 watt controller.

I haven't thought about any of this for a while. Not since adapting and building power supplies for the HURCO mill, so forgive me if I am a bit slow on the uptake here.

Pretty sure he does not have a regular 3 phase motor. IMO its likely a

was using a 20uF motor

After reading Jim's information and doing a little lookup of my own the motor at its core (just the motor) is likely a DC 3 phase motor. A conventional off the shelf VFD would be completely useless as they put out variable frequency AC or at most/worst offset symmetrical square wave variable frequency AC.

Cutting into the VFD and taking the output off the converter would kind of make the whole exercise moot. I hesitated to mention that as a possibility as it seems counter productive when (next paragraph).

What you need to look for I think is a 3 phase DC motor controller that uses pulse width modulation for speed control. There are a lot of them out there, and they aren't particularly expensive. Much cheaper than a VFD. Many of them can take variable signal voltage or a POT for speed control. Those that just use a POT generate their own signal voltage and use the pot as a signal divider. That exact application may be transparent to the user.

The issue will be voltage and current. While the input to the packaged controller seems to be 110VAC the output to the motor windings can be anything DC. You can work backwards to a limited extent, knowing its probably 1/2 HP (about 400 watts output) you can just use some form of (amps times volts = watts) to figure out a likely controller that shouldn't blow up as soon as you power it up. Its very likely not at the high end of the voltage spectrum since a buck boost transformer would add to the cost, but with very limited electronics it could be from any lowish voltage upto to 160VDC. 160VDC is the approximate result of straight bridge rectified 110V AC. A simple voltage regulator could drop that after the regulator or a simple transformer could drop that before the rectifier. You can likely look at the existing controller and figure some of this out. I would go with a nominal minimum 750-1000 watt controller.

I haven't thought about any of this for a while. Not since adapting and building power supplies for the HURCO mill, so forgive me if I am a bit slow on the uptake here.

While the name suggests that the motor runs on DC, actually the motor windings get AC created in a DC to AC power controller by magic crystals. DC has no phase.

Traditional DC-powered motors had brushes and a commutator to switch the current progressively around the rotor as it turns, keeping its magnetic field ahead of and pulling against the static magnetic field in the DC-powered outer windings.