3 phase to 1 phase wiring?

[old'un]

I have a 3 phase motor that I want to run on 1 phase 240 volt, have read a little on the subject but still a little confused as to the wiring and the terms Delta and Star, according to the plate it can run at 3 phase 400 volts Star or 1 phase 240 volts Delta, (dual voltage) but how do I wire the A B C terminals and if wired for Delta can I just plug it in or will it still need a converter/inverter?

[rbrowning2]

As i see it the motor was supplied for 400v connection only.

This means the star point, the common connection of the three coils, is inside the motor body.

To enable 220v three phase, you would have to dismantle the motor and locate the star point then bring out the three wires to a six terminal connector block.

Probably easier to buy a new motor with the six wires ready to use in either star or delta, you will then need an inverter to run the new motor in delta at 220v it will not work 220v single phase, as you still need the three phases generated by the inverter.

You could keep the current motor and buy a converter that converts the 220v single phase to 380volts three phase but not the best way forward as you lose the benefits of the inverter, speed control, jog, forward and reverse.

 

[bone]

On your N terminal should be 3 leads these will be the other ends of A,B,C leads through continuity test you will find the other ends A1-A2, B1 -B2, C1-C2.

  Put A1 - B2, B1-C2, C1-A2  back on the A,B,C,  terminal posts 

Put live on A post.  Neutral on B post. Then a constant run capacitor between A  and C post. That will be a trial because you have to get current and voltage as close to motor data plate or you will run hot. As a bullpark start of with a 15 micro farad constant run capacitor. Or failing that watch some tube conversions. Best of luck 

 

[Yellow Bear]

2 hours ago, rbrowning2 said:

As i see it the motor was supplied for 400v connection only.

This means the star point, the common connection of the three coils, is inside the motor body.

To enable 220v three phase, you would have to dismantle the motor and locate the star point then bring out the three wires to a six terminal connector block.

Probably easier to buy a new motor with the six wires ready to use in either star or delta, you will then need an inverter to run the new motor in delta at 220v it will not work 220v single phase, as you still need the three phases generated by the inverter.

You could keep the current motor and buy a converter that converts the 220v single phase to 380volts three phase but not the best way forward as you lose the benefits of the inverter, speed control, jog, forward and reverse.

 

This ^^^^^^^^^

[bigroomboy]

You can't run a 3 phase motor on single phase without some sort of phase converter to generate a 3 phase supply. Some motors can be switched between 400 and 240v but that's still 3 phase in both configurations

[bone]

 You can and I am running 2 fractional hp 3 phase motors as single phase in delta configuration with capacitors. 1 is an extractor fan the other is a shaker for a seed cleaner and have been for several years, no converter just capacitors

[bigroomboy]

Yes, that's also known as a static phase converter, all be it a home made one.

[old'un]

Ok, I think I understand what I need to-do, looking at the picture below I have taken the 3 wires off terminal N and checked for a circuit (continuity) between A, B and C and the wires from N being Brown, Black and White, so I presume I connect the Brown, Black and White to the A, B and C terminals where there is continuity and that will set the motor in Delta mode 240 volt 3 phase.

Looking at some videos it seems I then need something to convert my 240 volt 1 phase to 240 volt 3 phase, something like this? WEG CFW300 IP20 0.37kW ….https://inverterdrive.com/m/WEG/CFW300/?gclid=CjwKCAjw9pGjBhB-EiwAa5jl3PK0tYceJ1jvL7TH2hjVvM2qoeQyKyVqjidxXu94-qwGeXo4TXwivhoCgcMQAvD_BwE

 

[udderlyoffroad]

The documentation (PDF) of the Inverter/VFD you linked to explains it rather well:

 

It's one of the better VFD manuals I've seen, walks you through it quite well.

What is your application?

[old'un]

1 hour ago, udderlyoffroad said:

The documentation (PDF) of the Inverter/VFD you linked to explains it rather well:

 

It's one of the better VFD manuals I've seen, walks you through it quite well.

What is your application?

If by that you mean what machine it will be running then its for a Fobco bench drill.

Does my last but one post look correct with regards the connections of Brown, Black and White wires and the connection to A, B and C?

Edited May 19, 2023 by old'un

[udderlyoffroad]

24 minutes ago, old'un said:

If by that you mean what machine it will be running then its for a Fobco bench drill.

So, worth probably worth getting an inverter anyway for the ability to vary the RPMs if it's a bench drill.  Especially if you're doing mostly metalwork rather than wood.

You might want to put the unit in an enclosure, as apparently any swarf or dust that gets in the vents of the unit will quickly kill it.  I say apparently, as I've no direct experience of that.  I've only ever worked with large VFDs that are usually in their own cabinets, away from the pump they're running.

[old'un]

12 minutes ago, udderlyoffroad said:

So, worth probably worth getting an inverter anyway for the ability to vary the RPMs if it's a bench drill.  Especially if you're doing mostly metalwork rather than wood.

You might want to put the unit in an enclosure, as apparently any swarf or dust that gets in the vents of the unit will quickly kill it.  I say apparently, as I've no direct experience of that.  I've only ever worked with large VFDs that are usually in their own cabinets, away from the pump they're running.

Is it better to match the inverter wattage to the motor exactly, 370w or go up a step to say 750w, also speed? I presume that is dialled in on the inverter, the motor is rated at Hz50, if I set that on the inverter to Hz50 will I get the same speeds as when it was running on 3 phase 400 volts?

Yes, mostly metalwork.

[udderlyoffroad]

Maybe a bit of background info might be useful, forgive me if there’s an element of teaching your granny to suck eggs.

The whole point of an inverter – better described as a variable frequency drive – is to vary the frequency supplied to the motor, as frequency is proportional to speed – on an induction motor anyway.  So, whilst in the UK we nominally have 50 Hz, north America 60 Hz, and so on, most VFDs will output somewhere between 0-400 hz, depending on its settings.  This means you can effectively infinitely vary the speed of the motor (subject to a few restrictions).

Originally these were used in industry as means of controlling large motors, allowing for things like a gradual ramp-up of large machines, which could reduce electricity used considerably.

VFDs have become more and more affordable and for smaller motors, to the point where in industry if you *don’t* use a VFD, you need a bluddy good reason not to.  And now we have VFDs that hobbyists can use, especially those of us in the UK who don’t have access to three phase power.  The VFD can as easily generate three phases as it can one (within reason, your electricity supply still needs to be capable of supplying the total power it uses!)

So to answer your question, no you don’t need to match the VFD’s wattage to your motor, in fact a little oversize VFD is probably better.  If you just set the VFD to 50 Hz, then yes it will run at the intended RPMs, but that would be a shame, especially as your intended application is a bench drill.  Varying the RPMs to match the job is much easier and more granular on the VFD than it is by changing belts constantly.

Seriously, have a thorough read of the setup PDF I linked to above, it’s quite good as these things go.  I suggest you get yourself a little control box with physical start/stop  buttons and maybe a potentiometer for the speed control.  All cheap enough on ebay.

[old'un]

1 hour ago, udderlyoffroad said:

Maybe a bit of background info might be useful, forgive me if there’s an element of teaching your granny to suck eggs.

The whole point of an inverter – better described as a variable frequency drive – is to vary the frequency supplied to the motor, as frequency is proportional to speed – on an induction motor anyway.  So, whilst in the UK we nominally have 50 Hz, north America 60 Hz, and so on, most VFDs will output somewhere between 0-400 hz, depending on its settings.  This means you can effectively infinitely vary the speed of the motor (subject to a few restrictions).

Originally these were used in industry as means of controlling large motors, allowing for things like a gradual ramp-up of large machines, which could reduce electricity used considerably.

VFDs have become more and more affordable and for smaller motors, to the point where in industry if you *don’t* use a VFD, you need a bluddy good reason not to.  And now we have VFDs that hobbyists can use, especially those of us in the UK who don’t have access to three phase power.  The VFD can as easily generate three phases as it can one (within reason, your electricity supply still needs to be capable of supplying the total power it uses!)

So to answer your question, no you don’t need to match the VFD’s wattage to your motor, in fact a little oversize VFD is probably better.  If you just set the VFD to 50 Hz, then yes it will run at the intended RPMs, but that would be a shame, especially as your intended application is a bench drill.  Varying the RPMs to match the job is much easier and more granular on the VFD than it is by changing belts constantly.

Seriously, have a thorough read of the setup PDF I linked to above, it’s quite good as these things go.  I suggest you get yourself a little control box with physical start/stop  buttons and maybe a potentiometer for the speed control.  All cheap enough on ebay.

 

Thanks for the detailed reply, much of which I can understand, apart from the need for start/stop buttons and maybe a potentiometer for the speed control.

Will the switch on the side of the drill not function as start/stop and reverse?

Also with regards drilling speeds, I have been a toolmaker all my working life and can judge when a drill is running at the correct speed for any given metal, so I see no need for monitoring drill speed, unless that is for some technical reason.

I have read the PDF instructions.

[udderlyoffroad]

2 hours ago, old'un said:

Will the switch on the side of the drill not function as start/stop and reverse?

Thing is, one of the issues with a VFD is that there needs to be nothing, electrically speaking, between the VFD and the motor, just a cable.  So wiring a switch between the VFD and the motor won't work, or at least it'll only work briefly.

So, your options are, in order of (my) preference:

1. you may be able to adapt the  existing switch gear on the drill to control the VFD directly
2. you might have to get a box with buttons on it and wire that to the VFD. 
3. You can use the keypad on the VFD

For option 1, I know, for instance, people have adapted the old 'drum switch' on lathes, for to 'talk' directly to the VFD and replicate the forward-stop-reverse functionality.

3 hours ago, old'un said:

I have been a toolmaker all my working life and can judge when a drill is running at the correct speed for any given metal, so I see no need for monitoring drill speed, unless that is for some technical reason.

Think there might be a misunderstanding here.  I'm not suggest 'monitoring' the speed per se*, I'm suggesting that if you're going to all the effort of fitting start/stop buttons, you might as well add a speed knob, aka a potentiometer, to control the speed.  Far more convenient than changing belts the whole time.

*other than with your speeds-n-feeds sixth sense after a working lifetime ‘handle turning’…