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Y Start / Delta Run, but 'normal' Motor Y Run?

Y Start / Delta Run, but 'normal' Motor Y Run?

Y Start / Delta Run, but 'normal' Motor Y Run?

Ok, simple question I hope.

Normal for the U.S. (me anyway) 480 VAC 3ph, 9 lead motor. Internally lead #10, #11, & #12 are connected together, making it a Y motor. If this is normal, and it is in Y for run, why do we Start in Y and run in Delta?

Ok, this is what I am thinking... In Y we have to go thru 2 'winding sets' to get from phase to phase, and in delta we only have to go thru 1 'winding set'. Ok, makes sence, but...

Then we would need a 'special'(higher voltage) motor for Y Start/Delta Run. I mean, you couldn't just use a 12 lead motor and make it Y/Delta. The name plate says for high voltage:

and it mentions nothing for a delta connection. The motor runs fine.

So my question can be distilled to, can I just connect this motor for Y Start / Delta Run? Because it is already in a Y Run?

I am thinking that when I would switch it to Delta, it would be getting too much voltage in each winding. Isn't the Phase to Phase winding count 4 in Y, and only 2 for Delta (assuming High Voltage connection)

So the only conclusion I can come to is that for a Y Start / Delta Run motor, I need a motor that can handle Full Voltage in the Delta Configuration, and it would get partial voltage in the Y Configuration?

Is it this simple? or is there more to this?



RE: Y Start / Delta Run, but 'normal' Motor Y Run?

You are correct.

Wye start - delta run motors are specifically design and manufactured to run delta connected at the full final line to line voltage.

A motor with twelve leads can be operated wye start delta run providing the exact voltage line to line for the pretended final delta connection.

For instance a 230/460 volts 12 leads motor design to operate 2Y for 230 Volts and 1Y for 460 volts "can not be operated wye start delta run  for 230 nor for 460 volts."

However, it could be good Y-D for 132.8 Volts or 265.6 Volts line voltage. Those rare figures of voltage resulted from dividing the wye voltage by the squred root of 3.   

RE: Y Start / Delta Run, but 'normal' Motor Y Run?

"So my question can be distilled to, can I just connect this motor for Y Start / Delta Run? Because it is already in a Y Run?"

Answer can be distilled to "NO"

Long answer is that with the internal wye connected motor, there is no way to get a delta connection.  You are limited to 2 voltages and two rotations, that is all you can do with the connections.  Other means will have to be used if you need the effect of the wye start(applies less than normal (for the motor winding)voltage so torque and amperage are reduced.  


RE: Y Start / Delta Run, but 'normal' Motor Y Run?

It sounds like you have a dual voltage motor.  In high voltage (460V ?) the windings are in series, but as you said are wye connected.  In Low voltage (230V ?) the windings would be in a parallel wye configuration - probably:
(10-11-12 internal)

RE: Y Start / Delta Run, but 'normal' Motor Y Run?

You are confused by 3 different kinds of dual voltage motors and 2 kinds of single voltage motors except for easterm block countries. They are:

1. Single voltage wye connected motors. These usually have 3 leads but in larger sizes have 6 leads so that differential protection can be applied.

2. Dual voltage 1Y-2Y motors typically rated 230x460 volts, which is a US scheme. Some of these are robust enough to operate on 120Y208 volts and 240Y416 volts 60 Hertz and 380 volts 50 Hertz.

3. Dual voltage 1D-1Y motors rated 230 volts delta and 400 volts wye. These are used on Autrailian and some South American 60 Hertz systems which are 240 volts delta corner grounded or 240Y416 volts. One the 1D connection these can be wye-delta started.

4. Single voltage delta connected motors. If equipped with 6 leads can be wye delta started.

5. Dual voltage 1D-2D motors usually rated 230x460 volts which is a US convention. Some of these have only 9 leads and cannot be wye-delta started unless you take the motor apart and add 3 leads. If equipped with 12 leads can be wye delta started. There are also variations. You can permanently connect a 12 lead 1D-2D motor as a 1Y motor for use on a 416 volt system like in 3 above - this cannot be wye delta started. Lincoln Electric also makes some 12 lead motors that are 1D-2D 460x920 volts - these can be used as wye delta or part winding start on 480 volts.

6. If you want to go crazy, go to East Germany and a few other eastern block countries. They have 230x690 volt motors! These need 15 or 18 leads.

RE: Y Start / Delta Run, but 'normal' Motor Y Run?

Hi Randy,

The wye-Delta Starting is made in order to reduce the High Starting Current.

If you have a 9 Leads Motor,230-460 Volts, and you want to start in wye-delta the first stepo is to test with the metter if the lead number 7 gives continuity with the lead Number 2(You also can test number 8 with number 3 and number 9 with number 1),if not the motor is connected in Wye and you can´t perform a wye-delta starting. If the answer is yes you most send the mottor to rapair shop to convert this 9 leads motor in 12 leads motor now you can made the star-delta starting.



RE: Y Start / Delta Run, but 'normal' Motor Y Run?

I agree with Aolalde, despite theory not all motor windings are designed to or will run suitably at the higher voltage in delta. Generally anything under 4kw will start DOL in star at the higher voltage and perform, but above 4kw they are designed specificaly to run in delta and will lose power and torque if run in star. I also agree with Rasinbran as the motor in question could indeed be a dual voltage design suitable for DOL starting. Despite never having seen one the theory makes sense. A star to you both.....A single rated voltage and 9 leads could also mean a 2-speed winding but thats another story and the lead markings do not indicate this.

RE: Y Start / Delta Run, but 'normal' Motor Y Run?


A concrete answer, the motor you described is 9 terminal leads Wye connected. Two circuits Wye (the connection you described) is good for operation at 240 VAC. The following one circuit Wye connection is for operation at 480 VAC.
L1 to T1
L2 to T2
L3 to T3
Joint and insulate T4&T7; T5&T8; T6&t9
Terminal 10, 11 & 12 are internally connected.

Now, if you need this motor adequate for Wye-start delta-run at 480 or 240 VAC, a new winding must replace the actual with turns per coil re-calculated for delta connection and leaving six leads for one voltage or 12 leads for dual voltage.

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