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3 phase motor low voltage

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3 phase motor low voltage

Postby wallace » 15 Nov 2018, 11:08

The PK I just finished is going on a big boat to Canada, but before it goes I need to make it useable for their electrickery which is 220v 3 phase.
The tag on the motor reads 380/440v and has 6 wires coming from the windings. 3 joined together and 3 going to the starter.
Generally even though the tag doesn't say 220v/380v you can still wire it for low voltage. Is it just a matter of pairing the 6 wires to obtain the 220v
wallace
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Re: 3 phase motor low voltage

Postby 9fingers » 15 Nov 2018, 11:34

wallace wrote:The PK I just finished is going on a big boat to Canada, but before it goes I need to make it useable for their electrickery which is 220v 3 phase.
The tag on the motor reads 380/440v and has 6 wires coming from the windings. 3 joined together and 3 going to the starter.
Generally even though the tag doesn't say 220v/380v you can still wire it for low voltage. Is it just a matter of pairing the 6 wires to obtain the 220v


Yes but to be clear on "just pairing" you need to sort out the wires into three pairs that measure equal resistance such that no pair has a connection to any other pair. Note the resistance that you measure.

Take the first pair and connect one end (any end) to one end of the second pair (any end).
Take the free end of the second pair and connect it to one end of the third pair (any end).
Take the free end of the third pair and connect to the free end of the first pair.
You then have three connections to apply power to.
Measure the resistance from each connection to each of the other two. They should be equal and be 2/3rd of the figure you noted down above.

Be aware the most meter leads will add up to 1 ohm to the reading. Short the probes together before making a measurement and subtract this from each of your measurements.

Bob
Information on induction motors here
https://drive.google.com/file/d/1dBTVXx ... sp=sharing
Email:motors@minchin.org.uk
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Re: 3 phase motor low voltage

Postby wallace » 16 Nov 2018, 10:38

Thanks Bob much appreciated. I've been asked to find a couple of more machines and prepare the motors for Canadian power. Do you think it would be easier for the guy to make his supply suitable ie by using a transformer to up his 220V to 440V or by me potentially having to get a couple of motors rewound to 220
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Re: 3 phase motor low voltage

Postby 9fingers » 16 Nov 2018, 10:48

wallace wrote:Thanks Bob much appreciated. I've been asked to find a couple of more machines and prepare the motors for Canadian power. Do you think it would be easier for the guy to make his supply suitable ie by using a transformer to up his 220V to 440V or by me potentially having to get a couple of motors rewound to 220


I presume we are talking 3 phase motors here?

A 3 phase step up transformer suitable for a good few hp is going to be expensive and I'm not sure why you say the other option is for you to get motors rewound here?

You only need to get your rewind people to open up the star point and bring the extra connections out for 240/415 versatility (or hard wire them inside for 220 delta use only). A pretty simple job for single speed motors.
Note that 2 speed Dahlander connected motors will be more of a challenge in all respects.

Bob
Information on induction motors here
https://drive.google.com/file/d/1dBTVXx ... sp=sharing
Email:motors@minchin.org.uk
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Re: 3 phase motor low voltage

Postby wallace » 17 Nov 2018, 11:03

Thanks Bob, I wasn't sure if the bringing out of wires from the windings was always possible
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Re: 3 phase motor low voltage

Postby 9fingers » 17 Nov 2018, 11:07

wallace wrote:Thanks Bob, I wasn't sure if the bringing out of wires from the windings was always possible



I've not had one that would not succumb :D

Once a motor is wound the last job before impregnation would be forming the star point and adding flexible tails ready to bring out to the terminal box. So the star point tends to be fairly accessible with only a few cuts to the lacing necessary to tease it out.

Bob
Information on induction motors here
https://drive.google.com/file/d/1dBTVXx ... sp=sharing
Email:motors@minchin.org.uk
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9fingers
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