# 3 Phase German motor connection



## josesaucedo (Feb 17, 2009)

I have a German 3 phase motor that I have to connect to high voltage... The name plate shows delta and "Y" connection. Can someone take a look at the attached pic and tell me whats for low and whats for high connection.

Thanks.


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## Big John (May 23, 2010)

All other things being equal, your delta is gonna be low voltage and your wye is gonna be high voltage. 

In a delta full line voltage is applied across one winding (e.g. U1 to W2). In order to get similar torque at higher voltage you must divide the voltage across two impedances by putting two windings in series (e.g. U1 to W2 to U2 to V1).

This is often true, but not always true, and if enough leads are brought out of the motor it's possible to have high and low voltages in either delta or wye.


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## don_resqcapt19 (Jul 18, 2010)

With a 6 lead motor European motor, the high voltage does not correctly match our voltages. If the low voltage is 240 when connected in delta, then the high voltage should be 415 volts when connected in wye. 

Is this a motor designed for 50 hertz?


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## JRaef (Mar 23, 2009)

If it is designed for 380 to 400V at 50Hz then you can run it at 480V, no problem, other than it is going to spin 20% faster. If it is an oddball 380V 60Hz, you cannot. That's not likely if it's German though. 

And yes, Wye will be the higher voltage.


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## micromind (Aug 11, 2007)

As JReaf stated, it'll work just fine if the Voltage/Hertz ratio stays the same, or pretty close.

One thing to consider though, is what type of load is it driving?

A 50HZ motor operated on 60HZ will turn roughly 20% faster. In a lot of cases, it'll be overloaded at 60HZ, especially centrifugal pumps and fans.


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## Electric_Light (Apr 6, 2010)

What does the name plate say? 

In the US, wye is usually for starting only. A 480v delta-wye motor started in wye acts as if the motor is started on 277v and it's switched to delta once sufficient speed is reached, but the motor will burn out if you leave it in wye. The purpose is to reduce starting amps and prevent lurching. 

If it's a 380-400 50Hz motor
It will run fine on 460-480 60Hz, but it'll run at 1725 or 3450 rather than 1440/2880 and you have 1.2x the horsepower. (the torque stays the same, but you get more RPMs)


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## JRaef (Mar 23, 2009)

micromind said:


> As JReaf stated, it'll work just fine if the Voltage/Hertz ratio stays the same, or pretty close.
> 
> One thing to consider though, is what type of load is it driving?
> 
> A 50HZ motor operated on 60HZ will turn roughly 20% faster. In a lot of cases, it'll be overloaded at 60HZ, especially centrifugal pumps and fans.


Good point on the centrifugal pump issue, I should have mentioned it too. 

I just had to put a VFD on a pump last month solely because of this issue. At 60Hz, the pump needed more HP than the motor could safely deliver. It was a 10HP (7.5kW) 400V 50Hz motor on an Italian machine they bought on Ebay and had shipped over here (these people never think to ask someone about the electrical issues ahead of time). Although the motor wasn't fully loaded at 50Hz, at 60Hz (120% speed) the pump demanded about 16HP and the motor was only delivering about 12HP. IEC motors also don't have any service factor, so they couldn't keep it running. They could have just installed a bigger motor, but it was close coupled to the pump and mounted in an odd way. They also could have used a valve to choke the flow back to what it was at 50Hz, but the water was pumping whole fruit into a baby food processor, so no restrictions in the piping were allowed. I had never seen that before, the entire apple or peach went through the pump impeller, whole, then came out undamaged on the other side. I was told it's kind of common, I had just never seen that before.


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## micromind (Aug 11, 2007)

Electric_Light said:


> What does the name plate say?
> 
> In the US, wye is usually for starting only. A 480v delta-wye motor started in wye acts as if the motor is started on 277v and it's switched to delta once sufficient speed is reached, but the motor will burn out if you leave it in wye. The purpose is to reduce starting amps and prevent lurching.
> 
> ...


While I disagree with most of the European electrical strategies, they do have, in my opinion, a better power distribution system. 

While we have POCO transformers that operate at 120, 240 and 277, they have only 240. 

All single phase loads are 240, there's no 120. So a basic single phase service is 2 wire. No chance of burning stuff up because of an open neutral. 

3Ø motors are all 6 lead, usually 220/400 or 240/415. ∆ connection for low voltage, Y for high. Same with service transformers. 

In either system, 240 single phase is available without more transformers. 

Also, no possible problems with running a 230 volt motor on 208. Motor voltage always matches service voltage.


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## Electric_Light (Apr 6, 2010)

micromind said:


> While I disagree with most of the European electrical strategies, they do have, in my opinion, a better power distribution system.
> 
> While we have POCO transformers that operate at 120, 240 and 277, they have only 240.


It's more like our 480/277 that's operating at 400/230 50Hz. 

Residential power is served L-N. I believe the two common options are 230V single phase or 400v three phase.


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## southside (Jan 3, 2015)

*high y*

yes the high voltage would be the y..............up to 575............but you don't tell us what your voltage is


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## iamthor2 (Dec 9, 2014)

Are you people serious. Some fool posts a picture of the casting inside of a motor terminal box lid and asks how to connect it to high voltage and you Cowboys are ready to have a go.. Read the motor nameplate it has all the info you require, it tells you the connections for different voltages and the rating of the motor for those voltages and frequency.
Those Europeans know their **** you just got to learn to read.


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## JRaef (Mar 23, 2009)

iamthor2 said:


> Are you people serious. Some fool posts a picture of the casting inside of a motor terminal box lid and asks how to connect it to high voltage and you Cowboys are ready to have a go.. Read the motor nameplate it has all the info you require, it tells you the connections for different voltages and the rating of the motor for those voltages and frequency.
> Those Europeans know their **** you just got to learn to read.


No, it probably does not, and that's likely why he had to ask. Having worked for two German companies, I can attest to their general arrogance in expecting that if you are working on something, you should already know all of the conventions involved, so they don't have to tell you that. For example, Wye is the higher voltage, Delta is the lower. You are just supposed to know that, because it is ALWAYS like that in Germany. But if you are not in Germany, then you don't really matter and they don't feel a need to make it clear to lesser beings like us (in their eyes).


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## tceek (Apr 1, 2014)

the dwg shows only the Y and Delta connection. it does not necessary mean that you connect it to higher or lower voltage. It depends on the nameplate and the voltage you want to connect it. In some application you using a YD start up on the same voltage to start the motor. 

in regards to residential >> the service entrance to a house is 3Phase + N 230/400V.


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