single phase to 3 phase conversion
single phase to 3 phase conversion
(OP)
sorry, this is long
I have been reviewing all the information I can find on the subject, but still have a couple of questions.
I have a 7.5 hp 220v 3 phase motor on a recently acquired machine. The motor has a unique mounting plus the replacement cost and the need for reversing direction, prevent replacing with a single phase motor.
I have looked at using a separate 10 hp motor as a single phase to 3 phase convertor and using a VFD. Since this is for my personal use and not for a large company, cost is an issue.
First the VFD, at this size and voltage, all the VFD's I have found are three phase input. Even if I step up to 10 hp unit, I am concerned about the running single phase to the VFD. The soft start of a VFD would be a plus. Variable frequency is not needed. I have located a 10 hp 3 phase 240 VFD for $700.
When using single phase power to the VFD, it would appear that 4 of 6 diodes would not be used for powering the dc bus. What about moving the diodes so that all are powered by the single phase? Not sure I have the courage to open up the drive and start reengineering the drive. Also it would seem that if the drive was designed for three phase, that the dc bus would not be very smooth using single phase.
The rotary converter, I was planning on a 10 hp motor with the necessary start and run capacitors. My concern is efficiency and starting current. Having located a used 10 hp dual voltage motor, the total cost would be less than $300.
Your input and advice is appreciated.
Jon
I have been reviewing all the information I can find on the subject, but still have a couple of questions.
I have a 7.5 hp 220v 3 phase motor on a recently acquired machine. The motor has a unique mounting plus the replacement cost and the need for reversing direction, prevent replacing with a single phase motor.
I have looked at using a separate 10 hp motor as a single phase to 3 phase convertor and using a VFD. Since this is for my personal use and not for a large company, cost is an issue.
First the VFD, at this size and voltage, all the VFD's I have found are three phase input. Even if I step up to 10 hp unit, I am concerned about the running single phase to the VFD. The soft start of a VFD would be a plus. Variable frequency is not needed. I have located a 10 hp 3 phase 240 VFD for $700.
When using single phase power to the VFD, it would appear that 4 of 6 diodes would not be used for powering the dc bus. What about moving the diodes so that all are powered by the single phase? Not sure I have the courage to open up the drive and start reengineering the drive. Also it would seem that if the drive was designed for three phase, that the dc bus would not be very smooth using single phase.
The rotary converter, I was planning on a 10 hp motor with the necessary start and run capacitors. My concern is efficiency and starting current. Having located a used 10 hp dual voltage motor, the total cost would be less than $300.
Your input and advice is appreciated.
Jon





RE: single phase to 3 phase conversion
There is a discussion on this in thread 237-94610.
A 10 HP VFD on a single phase mains will be very difficult. I would say impossible. Single phase supply VFDs are not easily available above three HP.
If you rebuild a three phase unit by changing the rectifier, you will have at least two problems: 1) The inverter will probably report the missing phase and refuse to operate. 2) The current drawn from the mains will be higher than the highest fuse you are allowed to install. The current also has a very bad form factor, and that aggravates the situation.
A 10 HP motor HP on a three phase 400 V grid (as an example) would consume 16 A and needs at least a 50 A slow blow fuse (high starting current). A single phase inverter with 230 V input voltage (if available) would need 32 A if the power factor were 1. Taking the bad power factor into account, it seems more likely that a 63 A fuse is needed for reliable operation.
It looks like you will have a problem running your machine off a single phase supply. Are you going to run that machine at top speed and/or maximum load? If not, you may be able to reduce the power needed so that you can find an inverter that can be used.
RE: single phase to 3 phase conversion
What kind of control do you need-does the machine you are speaking of have a reversing starter with it, or is your supply expected to perform that function? If you only need something simple (i.e. no fancy functions or capabilities) the cheapest thing would be to build it, as the net cost of the devices would far less than any of the options you are currently pursuing, assuming that the inverter portion of the device is a simple square wave inverter.
RE: single phase to 3 phase conversion
RE: single phase to 3 phase conversion
Getting 3 phase installed at your house will be expensive if they power company would even do it. You will also most likely be charged industrial instead of residential rates. A better alternative is a phase perfect unit. www.phaseperfect.com This unit takes single phase and creates a clean third phase. You will not have variable speed or soft start capabilities with this, but if you need three phase, this might be the way to go.
Mike Bensema
www.dutchmenservices.com
RE: single phase to 3 phase conversion
These seem extra groovy…
www.aseapower.com/products/ac45-3.htm
RE: single phase to 3 phase conversion
Since I am in the middle of a buried electrical service area, three phase power is not possible.
I am going to contact Phase Perfect on Tuesday since this seems to be the best solution I have seen so far.
RE: single phase to 3 phase conversion
RE: single phase to 3 phase conversion
That was an interesting ref on phase converter (www.phaseperfect.com). Do you have by any chance used this product and if so, how would you rate it ?
Kumar
RE: single phase to 3 phase conversion
RE: single phase to 3 phase conversion
Sporadically, this is a fairly active topic at Eng-Tips.
Assorted information/products…
http://www.gwm4-3phase.com/
http://www.capacitorconvertors.com/staticinstructions.pdf
http://home.earthlink.net/~ojmsmith/indexd.html
http://home.att.net/~waterfront-woods/Articles/phaseconverter.htm
Some threads are…
Thread237-88925
Thread238-85149
Thread237-75783
Thread237-74389
Thread237-68085
Thread237-62718
Thread237-66357
Thread237-61099
Thread237-58717
Thread237-57678
Thread237-57678
Thread237-53938
Thread237-50067
Thread237-40497
Thread238-37887
Thread237-28750
Thread237-26789
Thread279-25652
Thread238-25659
Thread238-18786
Thread237-12936
Thread237-11842
Thread248-11407
RE: single phase to 3 phase conversion
My preference is to use VFDs since you can usually easily find one on ebay for a good price. I like the variable speed capability and the PP is a bit expensive. But if you have several 3 phase motors that need to be run, then the PP would be an easy solution.
Mike Bensema
www.dutchmenservices.com
RE: single phase to 3 phase conversion
As mbensema had indicated drive must be de-rated 1/2 to 1/3 the three phase sizing. Really you’re looking at a 20-25hp 230V drive. Your cost is going to approx double, it may not be practical if you do not require variable speed.
RE: single phase to 3 phase conversion
My opinion is that an electronic device solution is not necessarily the best for your problem. Single phase AC input rectification will be limited, reducing the power capacity of a standard drive. Add a phase devices could be a solution but check for real balanced 3-phases.
I suggest an old technology M-G set. Couple an old 15 HP single phase motor with an old Synchronous Generator. Recondition the generator from a junked Standby unit.
This will provide a pure generated 3-phase AC power.
RE: single phase to 3 phase conversion
Using a three phase input inverter on single phase is not a problem provided that:
1) The single phase voltage is equal to the three phase voltage, i.e. 220 volt three phase inverter used on 220 volt single phase supply.
2) The inverter is sufficiently oversized. This is necessary as the ripple current through the capacitors is much higher on a single phase inverter than a three phase inverter plus the current through the rectifiers will be higher. Generally, I double the inverter size. i.e. for a 7.5KW motor, I would use a 15 KW inverter.
3) The inverter does not have an input phase loss protection system.
Best regards,
Mark Empson
http://www.lmphotonics.com