Single Phase to Three Phase Conversion

At least three:
1) Single-phase motor driving three-phase generator.
2) VFD with single-phase input and three-phase output.
3) Rotary converter [capacitance induced delay(s) to create additional phase(s)].

Can u clarify vfd with single phase input & three phase output

I may be wrong, but I think it works like this:
The incoming single-phase AC is rectified and smoothed into a DC bus. From this bus, three branches are taken and inverted into AC with 120° intervals between, thereby creating three-phase output.
That's way oversimplified, but several manufacturers offer schemes like this, with literature available on the Web.

Tornado, you are right.

You are correct, it not over simplified, its right on the money.

FYI, ALL VFD's or VSD's work the same way, it doesn't matter if its 3 ph or single phase input, the input the rectified, the DC is inverted to give PWM output.

ps: GA from me!

Hi One & All,

What you are discribing is an uninterruptible power supply (UPS). I seen UPS used to convert single to three phase while I was in the millitray.

Ben

Except they don't have batteries or a charging control circuit so if the power goes out the thing stops.

Tornado has described a VFD, which in many process applications that type of controller is used

The difference between a UPS and a VFD (Variable Frequency Drive) is a UPS does NOT vary the output Hz & Voltage, whereas a VFD does.

But they BOTH work on the same principal. Input Hz to DC bus to inverted AC output(PWM)

However... you must remember the following.... a UPS has lead acid batteries to power the DC bus when the mains fails, a VFD does not.

If you read the OP question, he asks how many ways are there to convert single phase to three phase, which means you are also correct, as is everyone else

VFD is an acronym that stands for Variable Frequency Drive. If you want to know more about them then follow the link.

Describe what you are trying to do and why so that we don't think this is a student trying to get us to do your homework for you. This sounds like a homework question to me.

The two main types of 1 phase to 3 phase converters are Rotary Phase Converters and Static Phase Converters...It depends on the application...You can also match frequency...
http://www.3phasepower.org/rotaryphaseconverters.htm

Read this then come back with specific questions for clarification http://www.3phasepower.org/rotaryphaseconverters.htm

It really does smell like a homework question

Hi One & All,

If your is light enough 1hp motor you can use a "Static Phase Converters" with out the "IDLER MOTOR" of high load you need the "IDLER MOTOR" note table below on limitations plus you only get 2/3 the power out of you 3 phase load.

http://www.metalwebnews.com/howto/ph-conv/ph-conv.html

Let us know if this is helpful.

BEN

"NOTE: For the following outlined applications you MUST use a Rotary Converter"

This is totally False! Especially, a heating element will work on any waveshape you might wish to use, as long as the average(RMS) current is of a reasonable value for that heater. And where have you seen a three-phase heating element, anyway? A three-phase heater perhaps, but it would have three elements.

Most, if not all, the devices listed will operate correctly from an appropriate high frequency switching type three-phase supply with appropriate filtering.

How about some information on what you are trying to do?

For example, one suggestion which might be perfectly acceptable in one application could cause a fire, someone getting killed and someone (maybe you) going to prison in another application.

I have had good results with a rotary phase converter. (3 h.p.) I run a lathe and a milling machine off this.

oilcan13

you should either A: have youre elect company wire 3 phase to youre building or B: buy a 3 phase generator

A three phase motor will run on single phase power, but first, you must rope start it. It will then generate three phase so that you can start and run any smaller three phase motors on the circuit with it.

Really?

Yes, really. Very bad idea, I know of someone who lost a finger in the rope start, but it's sometimes called a "poor man's RPC".

Hi One & All,

I help set up and run a Single to Three Phase Power Convert and did NOT NEED a rope to start the the IDLE MOTOR!!! NOTE: starting capacitor! The device we were running was a Plasma Torch on table control by a computer to cut out designs. We had problem with the edges of the parts we were cutting out, they had rough edges.

We use a rotary converter and the problem went away! Then we used a three phase line filter on the output side of the "Single to Three Phase Power Convert" and this clean up the output enough to get a smooth edges we needed.

The list what not to use a "Single to Three Phase Power Convert" is true to appoint, but to get good results you may have to do something like use a line filters, lower power output to 1/2 power instead of 2/3 output, or what works. Remember that this system is exciting the other two currents from single phase input, which is a LITTLE "Slight of Hand" and may take some adjustment to get what you want out of circuit.

For light loads you do not even need to use the IDLE MOTOR!!

BEN

Cool!! Anything that can take a limb off has to be good!

Actually, I have found using a transformer is the most constant and simplest way to convert single phase to three phase power. Primary is wound for single phase and secondary is wound for three phase output. It works as designed, no rotary outputs, VFD is great if you are driving a large blower fan, because the soft start method was developed to help cut down on the ware of belts being burned off the pulleys, and also to help gain the most efficiency output of the drive motors.

I have a work associate who has such an item in his home shop. It was comparable in price to standard high current transformers, but it was worth every penny to have 200 amps 3-phase available in the shop. Just my 2 cents for now, Maximo

Details or link, Please!

Sorry, I have to call BS on this. How pray tell, do you get phase shifts on the 3 secondary windings?

Thanks, profG. I was wondering when someone would ask the question.

It can be done, you use a capacitor to create a pseudo phase shift just enough to cause rotation. They are sold as Static Phase Adders. Tehy say you lose about 20% of the motor power in the process, my experience is a little more, maybe 30% if it's something that needs a lot of accelerating torque. Mostly they are used for centrifugal pumps that do not.

http://www.angelfire.com/planet/eylander/static.htm

I can see how it would sort of work, but it sounds pretty dodgy to me.

If I understand "dodgy" to mean not the best method, I would agree. But unfortunately that rarely stops people who are looking for a cheap way out of a poor decision, i.e. buying 3 phase equipment when they have no 3 phase service, or being an OEM who doesn't want to make a single phase version of your product. Happens a lot actually.

ITT / Flygt submersible sewage lift station pumps are a prime example. Flygt, being Swedish, only makse 3 phase motors for their pumps and the motors and pumps are sealed together. But in a lot of far flung places in the US, the utilities do not run 3 phase services, only single phase. So Flygt here in the US derates their pumps by 25% for single phase service and ships them with a static phase adder in the control panel (unless the user wants a VFD).

Most recently we were talking about transformer w single phase input and 3 secondary windings, no? Rotation pretty much has no meaning in that context.

Dick

What I think they are doing is creating a split phase system with the transformer that gives you a neutral and two phases that are 180° out of phase, then by using a capacitor and the induction of the motor creating a third that is roughly 90° out of phase with the others. Instead of having three phases each 120° out of phase you have Phase 1 at 0°, Phase 2 at 180, and phase 3 at approximately 270° or alternative Phase 1 at 0° Phase 2 at 90° and Phase 3 at 180°.

It would probably work but the torque that the motor would produce wouldn't be very constant throughout each rotation, you'd get all the grunt round half the cycle with bugger all round the remainder.

Of course, but this would hardly be considered "200 amp 3 phase" service to a working shop!

Dick

This has been how I have been doing it since I figured it out about 18+ years ago.

No idler motors or rope starts and from every testI have done with my design I have not found it to suffer from the 1/3 power loss or low starting torque issue either when built correctly.

I run a commercial 15 HP three phase air compressor in my shop off of a 240 volt 60 amp single phase line and its can start down to around -20 F without problems.

http://www.electro-tech-online.com/re-projects/100563-3-phase-converter-schematic-miller-system.html