Converting 1ph motor to 3ph...

[Munkul]

Is this possible?
Its a Nederman extract fan that i want to adapt for a lower airflow application.
It looks to me like a regular induction motor with 3 windings, with a large capacitor across a pair to help with start up, wired in star.
I want to fit a variable speed drive, I've got one of those PWM type speed controllers but it doesn't have the umph to power it at lower speeds without cooking the windings (ie it's underspeeding and the motor warms up quickly)
Ideally, i take off the capacitor and feed it straight 3 phase from a small inverter. This would let it run a lot more efficiently and therefore cooler.
Alternatively... I could rewire it in Delta which would give a lot more torque and therefore less underspeed/phase imbalance at low speed... But it would take more amps and my pwm controller only has 6 amps to give anyway... And it would still have the same problem of amps/heat?

Can you all sense check this for me please? I'm not a sparky, i just know enough to be dangerous

 

[Onoff]

Suggest that the stator winding is wired for single phase?

Single Phase Motor schematics and working

This article explains basic construction and working principle of a single phase induction motor. Why single phase motor is not self starting? and how to make it self-starting?

www.electricaleasy.com

I'm guessing you won't have the 3 windings all the same resistance and in balance.

 

[dan.taylor.1]

Is that not a yank motor 110v 1ph 220v 3ph?

Pull the contactor and see what voltage it is, my extract is 110v, just runs off a big site transformer

 

[Agroshield]

It looks to me like a regular induction motor with 3 windings, with a large capacitor across a pair to help with start up, wired in star.

It is difficult either to confirm or deny that from the photo of the connection box you show.

My X-ray vision cannot see if there are three winding wires under the bus bars forming a star point. On the LHS of the connection box, it is not possible to see what is there.

Are there exactly six wires exiting the innards of the motor? Are they in three sets of two with very similar resistance between each pair?

If you zoom in on the data plate, the 'phase' part has a '3' overstamped with a '1'. That may or may not be relevant.

 

[Dcal]

Measure the windings and if they are the same, I'd say it's dual voltage.
If so, you can just junk the capacitor and run with an inverter.

 

[Dcal]

Also looking at the connection box, I'd put money on it being a three phase converted to run on single phase

 

[Agroshield]

Measure the windings and if they are the same, I'd say it's dual voltage.
If so, you can just junk the capacitor and run with an inverter.

But be very careful.

The data plate implies it is 110v/220v dual voltage.

If it does turn out to be three phase, it means it will accept 110v three phase wired in delta and 220v three phase wired in star.

The normal UK distinction between 'low voltage' three phase (meaning 220v) and 'high voltage' three phase (meaning 415v) will not apply as it is a US motor.

Bad things will happen if you wire it in delta and try to feed it 220v three phase...

 

[Dcal]

My bad.

Now I'm no expert, and I'm not pretending to be anything other than at the limit of my knowledge which is mostly from Jim Coxe's excellent book.

My take.
It's obviously a dual voltage motor 110v 220v.
Why would you wire it in delta if running on the higher voltage?
Looking at the connection box it's already in star. But of course the OP needs to check.

I think the only ssue is if the windings are the same or if it has a start winding.

At the end of the day, while it's not super efficient, everybody and their dog used to convert 3 phase motors to single phase so why would it be an issue to reverse the process even if it "is" a proper single phase motor? (Asking for a friend)

 

[Munkul]

Thanks for the helpful comments folks

There are 3 windings and it has 6 connections just like a normal induction motor. It takes 240v live and neutral input straight from the wall. Currently i have a 6 amp commercial kitchen extraction fan controller wired to it, but it sounds too laboured and runs hot at low speed - plus it won't start up at low speed.

My main takeaway from this so far is to undo the wiring and bus bars and measure the resistance of each winding to make sure they're all the same, and it does not have a start up winding.

If they are all the same, then I'm good to go with wiring a 240v VFD in 3ph star.

If they aren't all the same, then it has to stay 1ph.

 

[Dcal]

Also worth checking the resistance to earth and the capacitor while you are at it.

A clamp meter on the main feed in and / or on each winding can help identify issues.

Is their only one cap?
Most single phase motors will have two and a centrifugal switch, which should be the first place to start looking.
Can you hear it clicking in and out?

 

[Dcal]

Just thinking about this, it would be harder to run a single phase motor on an inverter as you would still need to disconnect the start winding, which would probably cause the inverter to throw a fault code.

 

[Munkul]

Also worth checking the resistance to earth and the capacitor while you are at it.

A clamp meter on the main feed in and / or on each winding can help identify issues.

Is their only one cap?
Most single phase motors will have two and a centrifugal switch, which should be the first place to start looking.
Can you hear it clicking in and out?

Just one cap, and its wired exactly like this diagram on Google for converting a 3phase motor to single phase. Far right

How to Run a Three-Phase Motor on Single-Phase Power Supply?

Running a 3-Φ Induction Motor on a 1-Phase Supply. A 3-Phase Motor can be run on 1-Phase Supply using Static Capacitor, VFD & Rotary Converter

www.electricaltechnology.org

 

[6ply]

Also looking at the connection box, I'd put money on it being a three phase converted to run on single phase

The data plate states "ph 1", in other words it is single phase. Moreover, it also includes the capacitor specification.

 

[Munkul]

The data plate states "ph 1", in other words it is single phase. Moreover, it also includes the capacitor specification.

Thats like saying a motor with 3ph on the data plate can never run on 1ph...but it's not quite true

 

[Pete.]

Being a fan motor that needs little start-up current it's quite possible that they have stuck a cap across 2 phases and called it single phase. I found one like that in an entry barrier.
The warning about 220v 3 phase is also valid I blew up the motor generator in my 10ee lathe because I stuck a 3 phase plug on it and put 415v into a 240v 3 phase setup.
Simple answer is take off the link plates and meter out the windings. If they are all similar resistance stick a vfd on it.

 

[My Old Landy]

But be very careful.

The data plate implies it is 110v/220v dual voltage.

If it does turn out to be three phase, it means it will accept 110v three phase wired in delta and 220v three phase wired in star.

The normal UK distinction between 'low voltage' three phase (meaning 220v) and 'high voltage' three phase (meaning 415v) will not apply as it is a US motor.

Bad things will happen if you wire it in delta and try to feed it 220v three phase...

Why would you think it is a US motor? It states 50 Hz not something they use. Also I believe they are a British company (well they were in the 1970's when it was made).

 

[knighty]

we're all just guessing what's going on inside

pop the wires of and check the resistance of the coils (and between coils)

that'll tell you straight away what's going on inside

 

[EBME2]

Does this cover it? Looks like a 2 phase motor for the US market, page 40 covers electrical connections.

https://www.airevalleyrewinds.co.uk/wp-content/uploads/2021/02/leroy-somer-single-phase-motors.pdf

 

[Munkul]

Does this cover it? Looks like a 2 phase motor for the US market, page 40 covers electrical connections.

https://www.airevalleyrewinds.co.uk/wp-content/uploads/2021/02/leroy-somer-single-phase-motors.pdf

Unfortunately that manual doesn't show the same connection set up that my particular motor has.

I'll be back in the workshop tomorrow night so I'll be able to investigate further

 

[Munkul]

Ok so i pulled off the cover plate again and found out 2 things.
1. It only had 5 wires from the windings to the wiring block. So not 3 phase.
2. The wires were massively overheated and the insulation fell off 3 wires without barely touching them, and a 4th wire was already shorting out against another one and was about 5 seconds away from shorting out altogether.
I'll strip it further and see if i can repair, otherwise I'll have to buy a new one shame, beefy fans aren't cheap to buy.