Author Topic: 3 phase from single phase  (Read 820 times)

xyzer

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3 phase from single phase
« on: February 23, 2018, 06:48:42 PM »
Is anybody out there converting on grid 220 volt single phase to 220 volt 3 phase? I'm needing to run a CNC 15hp 40 amps max. Not interested in building one just lookin for a good product that will give me stable 3 phase. The digital solid state ones seem to be priced up there. I also learned you need to upsize the converter about double to get good results. I have supplied a circuit with 100amps 220v to run whatever I go with. Rotary seems to be my $$$$ route. Looking for a been there done that reply that will keep me out of some of the potholes!
Dave
« Last Edit: February 23, 2018, 06:52:02 PM by xyzer »
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ajaffa1

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Re: 3 phase from single phase
« Reply #1 on: February 23, 2018, 10:15:58 PM »
Hi Dave, I have a couple of 3 phase spindle motors which run real well on variable frequency drives (VFDs). You require a VFD for each motor you wish to run as the VFD need to be programmed to match the motor.
Take a look at these: https://www.ebay.com.au/itm/Three-Phase-0-75-to-22-kW-Mini-VSD-VFD-Variable-Speed-Drive-Inverter-Compact/132374841729?hash=item1ed227c981:m:mXJKH_ayI6xJbCaBnyhiGCA.
These are cheap Chinese units, probably better to look at US or European units, more expensive but better quality.

Bob

ajaffa1

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Re: 3 phase from single phase
« Reply #2 on: February 23, 2018, 10:20:41 PM »
Sorry Dave the link I posted requires a three phase input. There are ones that run on single phase input, I`ll have a look and see if I can find some.
Bob


ajaffa1

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Re: 3 phase from single phase
« Reply #4 on: February 23, 2018, 11:01:31 PM »
Here is another one with a lot more technical data attached. https://www.ebay.com.au/itm/11KW-15HP-300hz-VFD-inverter-frequency-converter-1PHASE-220V-to-3phase-0-380V/172996296952?hash=item28476200f8:g:ygcAAOSwdSRaF99R

I believe the way these work is by rectifying the 240 v AC back to DC. The DC is then converted electronically back into three phase AC at the appropriate voltage. The frequency of that three phase is adjustable so that you can speed up/slow down the motor. Probably not a function you would require so you would set the maximum frequency to 50 or 60 Hz depending on the specifications on the motor. The beauty of these is that you can adjust the ramp up/down time so the motor winds up slowly and spins down slowly, improving motor life. You can also set forced braking by reversing the current to the motor, very useful for things like emergency stop buttons.
Have fun,
Bob

BruceM

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Re: 3 phase from single phase
« Reply #5 on: February 23, 2018, 11:07:56 PM »
Wow, those VFD/3 phase inverters are a bargain compared to the rotary converters.


ajaffa1

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Re: 3 phase from single phase
« Reply #6 on: February 23, 2018, 11:24:39 PM »
Hey Bruce, I run a couple of these in my joinery shop, wired to spindle motors. For tasks like routing or milling they are great as you can adjust the speed of rotation simply by turning a knob. I read up on them on various forums and there is some doubt about the quality of some of the Chinese units. I`ve never had a problem with them but I guess it comes down to price. I can buy three cheap units for the price of one US built converter.
Setting the parameters to match you particular motor can be a bit of a bugger, the better quality units have dozens of variables.
Bob

xyzer

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Re: 3 phase from single phase
« Reply #7 on: February 24, 2018, 08:32:14 PM »
Thanks for the replies, The CNC has several motors, Coolant pump, main spindle, and 3 servos for each axis. I also should have mentioned I wish to be able to use on other 3 phase equipment. 
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ajaffa1

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Re: 3 phase from single phase
« Reply #8 on: February 24, 2018, 10:29:41 PM »
Hey xyzer, If your CNC has a lot of sensitive electronics then a rotary converter should do the trick, chose one that has advanced voltage regulation to  protect computers and etc. Alternatively run the electronics off the 240 volt side of things by swapping out the transformer. I had a unit when I was in the UK made by a company called AmericanRotary, I bought it second hand for around 500 and it ran my spindle moulder and industrial band saw. It never let me down and when I emigrated to Australia I sold it for 500 so it cost me nothing. The only other piece of advice is that all this sort of equipment gets hot and has cooling vents, not ideal in a joinery shop full of fine dust particles. Either position it in a clean area or blow it out regularly with low pressure air.

Bob

xyzer

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Re: 3 phase from single phase
« Reply #9 on: February 25, 2018, 04:30:13 PM »
Thanks Bob I do have a smaller American Rotary I used on a smaller machine.  I've had the same experience. I'll probably follow the same manufacturer. 
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38ac

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Re: 3 phase from single phase
« Reply #10 on: February 26, 2018, 02:10:15 AM »
 I admit to being old school  but my rotophase convertor has been running my shop  for 15 years with out issue. I tried some of the cheap ebay vfds and even when up sized 3 times nameplate rating they would not run any of the machine tools I tried them on.  These are big old cast iron motors.  I threw them in a box and forgot about them
A vfd is a great drive, just not the cheapies. Also if your going to run more than one 3 phase machine the rotory can quickly get cheaper than a vfd for each machine
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gusbratz

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Re: 3 phase from single phase
« Reply #11 on: March 01, 2018, 07:20:41 AM »
I have static phase convertors on my lathe bridgport and air compressor. Basically just a capacitor that turns your 3hp motor into a 2hp cap start motor. they work ok but you lose 1/3 of the power. seems to work ok because old 60's stuff had way bigger motors than they needed anyway. I have an old used Allen Bradly VFD on my surface grinder and it seems to really choke the power. it is easy to bog the wheel down if you take much of a cut at all on it but it is only a 1hp cartridge grinder in the machine. if you put a pull cord on your 3 phase motor you can pull start it on normal biphase power in a pinch.