# 220 3 phase to 440 3 phase ?



## Scruffy (Dec 19, 2017)

I’m thinking of buying a old #5 brown and sharp surface grinder. It’s 440. I have 220 3 phase . Can you use a transformer to go to 440? If so how?
Thanks ron


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## Ulma Doctor (Dec 19, 2017)

you'll use a device called a step up transformer.
like this
https://hgrinc.com/productDetail/Electrical/Used-Olsun-Electrics-Transformer/09170250013/

basically the 230v as the input, the transformer output is 460vac, 3 phase.
the transformer is being run in reverse


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## Scruffy (Dec 19, 2017)

Thanks u
Ma, that’s what I thought.  Hgr. Is only a couple of hours from here so won’t have to pay a bunch of shipping if I buy the sg.
Thanks ron


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## Blackjackjacques (Dec 20, 2017)

Ulma Doctor said:


> you'll use a device called a step up transformer.
> like this
> https://hgrinc.com/productDetail/Electrical/Used-Olsun-Electrics-Transformer/09170250013/
> 
> ...



That is a 25 kVA transformer - I guess that will supply any future needs as well


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## Ulma Doctor (Dec 20, 2017)

the 25kVA is overkill, but the price is right!


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## Blackjackjacques (Dec 20, 2017)

Ulma Doctor said:


> the 25kVA is overkill, but the price is right!



Can't argue with that!


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## dwilliams35 (Dec 22, 2017)

It's often easier to convert the motors to 240v 3 phase than to get a transformer.  Normally it's just rewiring the motor, and either reconfiguring or changing out a much-cheaper control transformer.


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## Blackjackjacques (Dec 22, 2017)

dwilliams35 said:


> It's often easier to convert the motors to 240v 3 phase than to get a transformer.  Normally it's just rewiring the motor, and either reconfiguring or changing out a much-cheaper control transformer.



I agree - if the motor windings permit re-configuration - then it is a piece of cake.  Changing out a control transformer is also simple enough -if applicable.


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## Ulma Doctor (Dec 22, 2017)

A dual voltage motor is the prerequisite, otherwise the transformer may be the least expensive route


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## 1holla (Dec 23, 2017)

Check the specification plate on the motor. If 220/440V or 230/460 is given, just rewire the motor from star to delta connection. Check for control supply voltage also. On the terminalboard you will find 6 bolts ( 3 rows with 2 bolts), all connectet to the motor windings; 1 of each row to the supply. If 3 bolts of a line are connectet to the supply and the opposite 3 bolts are jumpered in line, that wiring is called star; if always 2 bolts of a row are jumpered and at the same time connectet to the supply it is a delta connection. That means a star connection is used for higer voltage and a delta connection for lower voltage. Do not touch the origin wiring of the motor windings.


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## Blackjackjacques (Dec 23, 2017)

I agree with 1holla and Ulma, IF the motor does offer access to the connections, going from wye to delta will reduce the voltage needs by a factor of 1.73 - that is, you can go from 440 to 254 V, etc.


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## 1holla (Dec 23, 2017)

for easier understanding here the corresponding schematics


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## Flynth (Jan 5, 2018)

Hi,

What does the motor spec plate say, can you post a picture? If it says 220/440 or 220/380 it is likely that it needs 3 phase power with each phase voltage of 220v up to 240v. This will result in a between phase voltage of 380v to 440V.

This service is usually called 3 phase 220V in US, in Europe and many other places.

However few places in the world (Bahamas for example) have real 108v 3 phase which results in a between phase voltage of around 220v. If you have a service like this you are likely to need a step up transformer.

It is hard to say without seeing the motor's spec plate. If it is missing but you can measure the resistance across the motor coils and measure the physical size of the motor. From this the power can be roughly estimated and voltage calculated based on resistance . If you are in doubt which service you have in your workshop and you have a multimeter that can measure AC voltages up to 750v at least and you feel confident it can be done safely you can measure the voltage between one of each phases and neutral and then between phases. However, if you have little experience with high voltage I would not recommend to mess with measuring voltages like this as it can be very dangerous.

I edited the post to add an explanation why I suggest to measure the physical size of the motor.


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