3 phase to 1 phase

The first question would be: how much power do you need to operate and what is nameplate information on the motor? Then, what does this motor doe? Are there any specific requirements on speed control or torque?

While not up on the actual technology available, such conversion is very feasible using modern electronics. If I were starting from scratch, I think I would rectify the line voltage and use pulse width modulation to convert the dc to 3-phase. The electronics could be fairly complicated, but I would not be surprised if there is a relatively low cost chip to do all the complex job that could be connected to suitable transistors or thyristors.

Your best bet is to Google for vendors supplying frequency conversion equipment.

You can use a single phase to 3 phase converter but they may be more than you want to spend. I would check with the manufacturer and see if they had that unit with a single phase motor and could you buy the motor.

The cheapest way I know of is to get a surplus 3 phase motor larger than the one in the balancer and some trivial components (like a motor starter capacitor). The surplus motor is powered by the single phase 240V feed and acts as a generator, generating three phase. You just connect the A B C phases of the load to the A B C phases of the motor.

I don't remember any further details, but Google is your friend.

Static converters work for all but hard to start motors such as 3450 RPM or higher speed motors, motors with direct coupled high inertia loads, or motor designs with inherently low starting torque. Most 1725 RPM 3 phase motors will start easily with an appropriately rated static converter, but the wheel spin motor on a balancer might be an exception as the ones I have seen start fairly slowly due to the wheel inertia. Since these motors are fairly small a single phase input Variable Frequency Drive might be a better alternative, but this requires rewiring the motor contactor to the VFD RUN control terminals and direct wiring the VFD to the motor. Either way you will need to be sure the single phase loads in the machine are powered from your single phase line, with only the motor connected to the derived phase of a static converter or the output of the VFD.

A quick check on eBay turned up a couple of single phase Hunter DSP

9000's for around $800, which might be more economical than getting a converter for the 3 phase machine unless you are getting a really good deal on it.

A rotary converter would also work, but with additional size and expense.

The cheapest way is to replace the 3 phase motor with an equivalent single phase one.

VFDs were mentioned, and yes in general that can be done. Normally, one sizes the VFD at double the rating of the load if using it in this fashion (single phase in, and three phase load on the VFD output). E.g., if the load is rated 10A, 230V, 3 phase, then the VFD should be rated 20A, 230V. The VFD will pull in a lot more than 10A on each of the two energized input phases, in order to deliver 10A out on each of the three energized output phases, and therefore needs to be rated higher than 10A to handle that higher input current.

The VFD input current distortion will be very high. If this load is a fair portion of your total load then this can become problematic.

VFD output voltages are kind of tough on motor insulation. The VFD output is a PWM waveform with pulses that have a very fast rise time, which travel down the wire and reflect, leaving the motor insulation subject to voltage transients up to about 3x the nominal motor voltage. Over time this can break down the winding insulation and cause the motor to fail. Where I am, it is madatory that a motor that is connected to a VFD be rated and labeled as 'inverter duty rated' (NEMA MG part 31) for this reason. I do not know whether that is the case where you are. I have heard it said that motors with Class F insulation and SF 1.15 are generally able to handle being powered by VFDs fairly well. But, caveat emptor.

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shop. The problem is it is 230 volt three phase. I only have single phase available to me.

or what is the cheapest esiest way to make something like this work?

The balancer is 300 dollars. I would prefer a single phase unit, however I live in a small area in Kentucky and not alot nearby. And of course shippin g on such an item would be very expensive if purchased online. I called the manufacturer and he said he would get me a price of the compon ets needed to convert it but that it would probably be more thna I would wa nt to spend. It would require a single phase motor, a new board, as well as of course the plug.

I have read conflicting things on using a converter on a balancer. Some say only the motor should be 3 phase and everything else within the unit shoul d be single. Others have said everythign within is three phase. I have read that you cant use a vfd or static converter. I read rotary converters have very unplanced voltages on each of the legs so I wonder if this would affe ct the accuracy of the balancer.

Kind of frustrating...

Without having either the balancer or it's schematic available the questions you posed are unanswerable. You need to provide more information to get anything other than suggestions of things you can look into as already provided.

It is highly unlikely that the balancer computer/controler runs on 3 phase power. Most likely it will be powered from only 2 of the 3 input leads, possibly through a single phase 230/120 control transformer. You need to find or create (from inspection of the machine) a schematic for power input to the machine controls including the rating of any transformers, fuses or circuit breakers.

The motor nameplate will have the information required for specific motor power recommendations. Essentially all info on the label is required, including any design designation, insulation class, service factor, voltage, full load current, or pretty much anything else on the label could be significant.

Existing motor control means (contactor? - rating, overload element size, source of control power, auxiliary contacts used/available) will also influence your options.

All of your options could easily be botched, but one or more are certainly viable if done correctly.

Although I am a bit rusty on the subject, I believe this will not work with induction motors. An induction generator requires a source of (what I think is leading) reactive power that it normally gets from the grid it is connected to.

The torque on a 3-phase motor driven from a clean source is rather steady. For a sing;e phase motor, the torque will pulsate. The inertia of the load will smooth out the effects. Even a capacitor run motor will not provide uniform torque. I suppose that might be a problem for some delicate balancing tasks. I presume you know that there can be instabilities in spinning devices that balancing cannot cure.

If you only had to run very light loads, a three phase motor will run (inefficiently) on single phase if you can get it started.

Rotary converters based on standard induction motors should include capacitors between the single phase line connected motor terminals and the derived phase motor terminals, also sometimes a power factor correction cap across the single phase line. One design I have seen posted on the rec.crafts.metalworking newsgroup used a 5 HP motor with 60 uF and 50 uF capacitors to the derived phase, with an additional ~300 uF motor start capacitor temporarily connected across the 60 uF run cap for starting. and a 50 uF power factor cap across the line. Current and voltage balance will never be perfect with a rotary converter based on an induction motor with capacitors, but it is good enough to power 3-phase motors in a home shop where the motors are not generally run continuously at full power.

There are a number of variations on the rotary converter in use including use of fixed capacitors large enough to start the load without a starting capacitor, and the rope-start converter where a rope wrapped around the motor shaft is used instead of the starting capacitor. The rope-start version will even run and power a smaller load with poorly balanced power without any capacitors at all; the single phase line provides enough reactive power to keep a lightly loaded 3 phase induction motor running once it has been started.

Better rotary converters use a special multi-tapped single phase transformer with a non-standard induction motor winding to produce very well balanced 3-phase power using no capacitors. This design was once widely used in electric locomotives, and is described in detail in "Principles of Alternating-Current Machinery" by Lawrence and Richard,

4th ed 1953 (the classic book on the subject). I don't know if these are still made but I have seen them show up at auctions occasionally.

The static converter is a box of capacitors only, using your motor(s) for the other half of the converter, suitable for powering motor loads only and typically even more imbalanced that a homemade rotary converter - but also cheaper to build yourself and often well suited for the home shop.

The VFD is also designed for driving motor loads only, and some care must be exercised when using them with standard (not inverter rated) motors, however if mounted very close to a 240 volt motor (short wire from inverter to motor) or if the optional output filter is purchased with the VFD (or better yet use the output filter and a very short cable for minimum chance of EMI problems, possibly also use the optional VFD input filter if sharing a power feed with sensitive loads), and the motor is never run at reduced speeds except during ramp up to 60 Hz on start and ramp down on stop, and good wiring practices are followed to keep VFD noise out of the control system, then the VFD will provide the motor with well balanced 3 phase power and operation as good as with a utility 3- phase feed can be expected.

Can you find a surplus 3 phase motor of a larger HP size. drive it with a smaller single phase motor (the idea is simply to run it near synchronous speed) and supply single phase to two of the phases- and connect all 3 phases to the balancer. This is an old farmer's trick in rural areas where only single phase is available.

Essentially it will work- even without the capacitors -in which case an external drive is needed to get it up to near synchronous speed. Surplus induction motors are more readily available than synchronous machines.