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Running a 3 phase machine from a singe phase supply.

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Lbob

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Does anyone know if more torque on the motor will be achieved by supplying a 3 phase machine with electric through a single phase invertor?

Specifically could I run the Felder K-700S panel saw (which has a 300mm blade powered by the standard fitted 4kw three phase motor) off my 50 hertz 240 volt single phase supply?
And enjoy the benefits of more power when sawing planks of timber.
I just wonder if anyone on the forum has such a set up and how does it perform.
Many Thanks.
 

Quickben

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I'm also looking to do this in the future, and, as far as I know, you lose around 10% of the power depending on the rating of your inverter.

I'm almost certain you don't gain power.
 

Ttrees

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Why do you want more power than 4kw?
My 3hp Startrite with Chinese VFD rips iroko at full capacity without breaking
a sweat, never bogged it down, I don't think.
Maybe some timbers are harder cut than iroko though?...
or could it be the case that you've got used to using a dull blade or something?

Tom
 

Lbob

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I have a C3 31 perform Hammer combination machine and it bogs down easily when sawing.
The motor is 3kw (4hp)
 

Sideways

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My impression from looking at second hand felders is that they didn't / don't fit dual voltage motors as standard. You have to specify it as an option when you order the machine. First step would be to check that your motor is compatible with a 240v single to three phase VFD.
Second point is that to get more torque for a given blade RPM you need to input more power. Some motors have a higher rated power at 60Hz rather than 50 Hz, so you could use a VFD to drive the motor according to it's 60Hz characteristics. That would spin it faster so you'd then change the pulleys inside to keep the blade speed the same and gain a little torque. A lot of faff for little reward. Cheaper to change the motor but as the earlier poster said I'm curious what you're cutting to need so much power in the first place.
I've just rebuilt an old industrial saw and even though I've fitted a 4kW VFD to drive the main blade I've fitted a 3kW motor as I want to limit the total load of main + scorer and the losses of two VFD's to a single 32A circuit. There's a limit to how much grunt I need in a domestic garage even spinning a 14" (max 16") blade !
 

Lbob

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I was cutting a batch of tanalised 45mm thick softwood recently.
Probably high moisture content.
I didn't think it would have struggled as much.

I notice my hammer machine does't have easy access to the motors.
 

Lbob

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I guess I could just drop in a 10" blade and put up with it.
 

Trevanion

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Lbob":rngehl9z said:
I was cutting a batch of tanalised 45mm thick softwood recently.
Probably high moisture content.
I didn't think it would have struggled as much.
Do you have an adequate blade fitted? I've run saws that were less than 2HP through much harder and thicker material with ease. There's no point to this thread if you're using a 90 tooth negative rake blade ripping up tanalised wood when you could be using a 24 tooth positive rake blade which will absolutely chew through anything you throw at it.
 

RogerS

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Lbob":1s6v2ih1 said:
I have a C3 31 perform Hammer combination machine and it bogs down easily when sawing.
The motor is 3kw (4hp)
What are you sawing ? Is the blade any good. I have (reluctantly) also a C3-31 and it rips OK ...unless the wood has a lot of stress inside it and the rip tries to close up after the riving knife.

Mind you, mine is 3-phase and it sounds as if yours is single phase.
 

Myfordman

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Lbob":2q0cup6w said:
Does anyone know if more torque on the motor will be achieved by supplying a 3 phase machine with electric through a single phase invertor?

Specifically could I run the Felder K-700S panel saw (which has a 300mm blade powered by the standard fitted 4kw three phase motor) off my 50 hertz 240 volt single phase supply?
And enjoy the benefits of more power when sawing planks of timber.
I just wonder if anyone on the forum has such a set up and how does it perform.
Many Thanks.
A correctly programmed, vector type inverter can potentially deliver a little more torque than a fixed 3 phase supply as it will have to capbility of increasing the voltage and hence power into the motor when it senses that the motor is slowing down. Limiting factors are the rating of the inverter itself and the limits programmed into it some of which are fixed at manufacture to protect the circuitry and some that are programmed by the user. Simple V-F converters will NOT have this capability so you need the correct type.

However, If your 4kw saw is bogging down on 45mm timber then it needs looking at maybe from the point of view of the blade needing fewer teeth, needing sharpening or belt tension needs adjusting - no more than 12mm play on the longest belt run. Belts do wear and need adjustment even replacement at times.
If your current machine is single phase, then additionally you could well need a new run capacitor fitting.
 

deema

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with a 4KW motor it shouldn’t matter what blade you’ve got in it (for stalling) , it shouldn't stall on what your cutting. If you’ve got the wrong blade it’s more likely to kick back and create a new opening in something with that power!!
The only thing that could cause what your suggesting I can think of is the motor is single phasing. This is caused by one of the phases having failed. Bad connection or a motor winding burned out. If it is single phasing power is dramatically reduced and the motor won’t last too long if the missing phase it’s not connected. Check continuity / resistance of each phase.
 

Lbob

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My machine is a single phase machine.
The blade is 315mm diameter and 28 tooth positive rake for ripping.
Made by Felder. From its last sharpening at the saw doctor it hasn't done a lot of work.

I notice on the motors, capacitors are not visible.
Thanks for all your help.
 

Lbob

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I've no idea how the motors could be removed from this machine without actually tipping the machine on its side.
 

Trevanion

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As everyone else has said, trying to access inside of Felder stuff is an absolute nightmare. I think it's mostly so that you call out a Felder Tech to look at problems rather than diagnose it yourself, I miss machines where you could undo a couple of bolts and it would come apart. As you say, you might have to tip the machine to get the motors out or you might have to take the tables off, which will be a can of worms. I recommend phoning Felder about the problem and ask what could be done, they're usually pretty helpful. I know on some of the older Felder gear that the capacitors are separate to the motors, So it might not be in an obvious place.
 

RogerS

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If it's like the Hammer C3-31 then the top is hung by screwed threads in the top and suspended from above and dropped in. I have no idea how I would get mine fixed if ever something went wrong. I guess the good thing is that I left it on the pallet !
 

deema

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Lbob":28wv9a07 said:
My machine is a single phase machine.
The blade is 315mm diameter and 28 tooth positive rake for ripping.
Made by Felder. From its last sharpening at the saw doctor it hasn't done a lot of work.

I notice on the motors, capacitors are not visible.
Thanks for all your help.
Then why ask how to run a 3ph motor using a VFD from single phase in your opening question?.?.?
 

Lbob

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Because I would consider selling my machine and buy a three phase machine.

A family member has just had a three phase motor fitted which powers a vacuum pump. The installers fitted an invertor connected to his single phase supply.
I read somewhere many moons ago that some people were running three phase lathes from invertors on their single phase supplies .
I think the biggest advantage here is speed control as I think the three phase motor retains its torque at low rpm's a lot better than single phase speed control.
So I've always thought it provided more power also.
 
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