delta-delta instaed of star-delta

[superdumpy]

hey guys,
Would connecting a three phase star-delta motor as delta-delta cause a burn out at a later stage? any info would be a great help.

 

[rbulsara]

No it will not burn out a motor. However there is no delta-delta motor. It will be just a delta motor and your starter and motor branch circuit will have to be sized for direct on line (full voltage) start. As long as the electrical system can handle the starting current, there should not be a problem. This of course assumes that the load does not have issue with hard start. Most loads would not, specially if it was happy on star-delta.

In fact star-delta motors are basically designed to start and run in delta. The connections are modified to a star conneccetion during a start, only to reduce starting inrush curret, but at the expense of starting torque and acceleration.

 

[waross]

The star connection is the starting connection. The delta connection is the normal running connection.
yours

 

[aolalde]

Could you explain how the Delta - Delta connection was done?

 

[powerjunx]

Hi, superdumpy.

I think you're talking about Part-Winding motor control configuration.

Delta-delta; first half delta-starting, second half delta running.

 

[rbulsara]

fbcybil:

The guy said it is a motor which has a star-delta starter. So there are not two sets of windings. Only six leads are brought out. It is a motor meant for either star-delta or just delta.

 

[powerjunx]

rbulsara, i got your point!

"three phase star-delta motor" is different to " star-delta starter"


Since, information were insuffecient as posted.. what we got here is usually to have an educated guess.

I'm just having an alternative suggestion.


regards.

 

[oldfieldguy]

A six-lead, single winding motor can be connected for either of two voltages. For example, a 4000-volt winding can be connected as delta for 4000 volts or wye (star) for 7000 volts.

Had a rewind shop do me the "favor" once. My motor that left with 2300-volt windings came back with 4160-volt windings. The site technicians connected it just like before the rewind, and it wouldn't develop torque.

There was an interesting conversation over that little faux pas.

 

[wrsharper]

We use star delta 12 tap motors that start in a series star and then become parallel deltas after transistion.

 

[rbulsara]

unless the motor nameplate indicates dual voltage and dual HP it is only meant for one setup. Even if it is used as what oldfieldguy suggests, it will run as either one winding star or delta but not both in one connectio (as you would have only one voltage system at the motor circuit)

Six lead motors with single HP and voltage rating are meant to run in delta and is permitted to be connected in star for starting period only at the expense of starting torque. This assumes the motor is intened to be used near its rated HP.

 

[superdumpy]

thanks for all the replies. it has helped a lot. the best eng. forum in town.

tommy