# Delta vs Wye



## SteveO.

There are lots of factors to consider but simply put, a wye motor will typically be physically larger than a delta motor of the same voltage and horsepower, which means more wire to wind it and more cost. The reason is that in delta, full line voltage is applied to each winding in the motor and in wye, the windings only see phase voltage (root 3 less than delta) so for the same HP, more current is needed. Usually wye motors are more common for smaller sizes and I haven't seen many in larger applications.

From the other angle, the same windings connected in wye or delta will produce different effects on the circuit and the load. While connected in wye, the motor will draw 1/3 the current that it will in delta, which is great for starting, but it will also produce 1/3 the torque, which can be good or bad, depending on the load. This is the reason you see wye-delta starters and wye-delta motors. You can limit the inrush current to the motor and not hammer a load with a big mechanical shock while starting. If you take a small (1hp) motor and start it across the line in wye, it will start smoothly but if you reconnect it in delta and start it, the motor will "jump" because of the torque.


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## micromind

First, the connection of the incoming power system has absolutely no effect on a motor wound either way. A delta motor works as well on a wye system as it does on a delta. The same goes for a wye connected one.

Generally speaking, a 3ø closed delta will tend to balance voltage at the expense of current. This is true with motors or transformers. 

Because of this, most smaller motors are wound wye. A small motor wound delta and powered by an unbalanced source will very likely overload one of its windings as it attempts to balance the voltage. A larger motor can affect the source a bit more. 

This is also why the majority of 480 to 120/208 transformers are delta primary. 

A 6 lead motor that is connected wye for high voltage and delta for low is an exception to the above. These motors are dual-voltage, but the two voltages are not half or double like a 9 or 12 lead one.

The high voltage is 1.73 X the low. This is because the power system that supplies them uses only one transformer secondary voltage.

For example (Frenchelectrician knows this better than anyone) a lot of European systems are 240 volt. No 120, just 240. If 3 transformers are delta connected, the result will be 240 across any two phases. If the same transformers are connected wye, you'll have 416 volts. 

A typical European motor will be 240/415 volts. The motor is connected the same as the transformers. 

Here in the US, a variation of this system is used sometimes, I've seen plenty of motors that were 2400/4160 volts. 6 leads, delta for 2400, wye for 4160. 

In some ways, the European system is better than ours. There is only one transformer voltage. Here we have 120, 120/240, 277, and rarely, 480. Also, the motor is fed the proper voltage, not like our 230 volt motors operated on 208.


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## John Valdes

Here is a drawing courtesy of Bob.


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## Awg-Dawg

John Valdes said:


> Here is a drawing courtesy of Bob.


 
I saw the drawing and it peaked my interest.

I've wired hundreds of motors just really never bothered to find out why they were wired differently.

Lots of good info here, Thanks


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