Electrical motor rewinding

You should consider putting transformers on the electrical supply to convert from 3ph 480v to 1ph 240v.

The motor horsepower (kW) will determine the kVA rating of the transformers required. The motor duty cycle and application will also contribute to sizing the transformer.

More info needed.

Re: Electrical motor rewinding. "How to convert a 3 phase 400 v motor to 1 phase motor 240 v." You are making a statement but do not tell us how convert a motor.....

I assume however you are asking a question. If so do not attempt to rewind a motor without first acquiring the necessary skills and techniques lest you ruin a perfectly good motor and not achieve you objective.

I suggest you follow the advice of CoronaCameraMan and use transformers.

What brand/model is the motor? Some motors have the capability to be wired as 3 phase or 1 phase. One way to tell is to look for a nameplate on the motor. If it is capable of being wired to run on either, it should have a wiring diagram telling you which wires to connect together to make it run on 3 phase and vice versa.

There are many ways:

1) You can do follow Mr.CoronaCameraMan, but must to install more a big Capacitor to motor.

2) Use phase converter.

3) Use transformer 240-400V and add Frequency Inverter Drive with single phase input 400V and 3 phase output 400V.

Good luck.

Depending on HP, buy a new single phase motor, or use option 3) buy a transformer and a VFD to generate the 3 phase.

To bench test 3 phase equipment at limited HP (2 Hp) I bought a rotating phase converter. It works well for the limited HP, but is not a practical solution for long term use.

For a customer who only had single phase 240vac and a juice bagging machine with 3 phase requirements for the drive wheels I used a small (oversized) VFD set at line frequency and voltage. The small motors would be started across the line and every thing worked well.

The application often determines the most cost effective solution.

Firstly, you cannot rewire such a motor, even rebuilding the motor is likely to be not worth the effort and costs, just buy a new motor and sell the old one......or get the electrical company to lay a 3 phase connection is really the best idea of all.....

Please remember that generally, 3 phase motors are used where a lot of shaft power is needed, a single phase motor will not usually have the power requirement and you have the problem of getting enough electrical power over a single phase to do the work required anyway......

eg. what you are trying to do is completely and utterly pointless......

If it is for knowing technical feasibility yes a motor can be rewound .But from cost considerations buying a single phase motor is likely to be the best and cheaper option.

nam70 gave up to now the best suggestion.

Let me start from beginning:

To rewind the 3-ph to 1-ph is practical only if existing 3-ph motor runs directly load/machine with specific coupling so any mechanical replacement is almost impossible.

3-ph motors maybe run from single phase power supply just by adding capacitors. In the case of 400v winding it is hard to deliver required current from 240 V source so there is a slim chance to reconnect coils inside the stator and connect them in parallel so rated voltage becomes 400/2 = 200v and the configuration with capacitors may work. Is it possible? Maybe but required a person who is working in this trade / have necessary skills. Also be prepared that output power on the motor shaft will be lower!

Hi Suds,

I am sorry, and must to post again. If your 3 phases motor is 220v/380(400V), you don't need to install a transformer,else have to use it.

There are many above solutions for your problem.

But sorry, can I ask you some questions again?

What power(HP or KW) is your single phase 240v motor?

Where is the 3 phases 400v motor using now e.g. in the "turning machine" or "milling machine",...? And now is not there 3 phases power supply at your place? And what purpose is your new istallation of new motor?

Re-winding an electric motor is not cost effective. First off the stator already has nine sets of three-prebent coil assemblies. These coils are over-laid upon one another, and then welded together in series to give you three seperate phases. The armeture is then wound in the same fashion with a smaller gage wire to give a specific out-put of voltage.

To re-wind a 3-phase motor to a 1-phase design is like re-inventing the wheel and the cost to convert is 3 times the money compaired to just buying the correct rated 1-phase motor. It is to your advantage to purchase a 1-phase to 3-phase transformer to power this 3-phase device you already have.

3-phase appliance is designed to save money in the power consumption used to make this item run. It will cost you more money to run a 1-phase unit over a 3-phase unit anytime it is used. The price of a transformer will be less to set into place and use over the wasted funds to convert to an energy sucking device.

Good luck on this one.

Maximo

3phase motor can be rewinded to single phase . but it has a limitation

firstly the capacity will be reduced and normally upto 2hp only single phase motors are made due to economical and practicl reasons

it is more profitable if an old 1 phase motor is converted to three phase then the power rating is aproximately double you will get

if you see the same capacity motors of single phase and three phase then you get the defference

thank you ANIL

It seems that somehow rewinding would be a solution. before the start of this surgery you must be award of its limitations.

Doing rewinding, in the past, I NEVER did it without:

1. Having wiring diagram of the existing motor (# of coils per phase, # of turns per coil, geometrical configuration etc.)

2. Recalculations for the new application (single-phase) with full calculation of the output (shaft) power with selected capacitors in a new internal circuit diagram for start/inrush transient and continuous run. If Out/shaft power/torque is not proper for its mechanical application load there is NO SENSE to do rewinding. As well as motors over 50 hp/ 35 kW range

In mentioned case of small motors where it is expected some power/torque reserve after rewinding it is necessary good thermal insulation conditioning and to do several hours no load & full load run test.