Star delta winding selection for motors
Star delta winding selection for motors
(OP)
What is the basis for selection of star/delta winding for motors ? If we chage the connection of an existing star motor to delta or vice versa , what will be the impact ?





RE: Star delta winding selection for motors
Advantages
Star connected motor phase voltage is 1 / √3 of supply voltage, therefore motor phase starting current is 1 / √3 times that when connected delta. The motor line starting current is therefore 1/3 times that when connected delta.
Disadvantages
Star connected motor starting torque is 1/3 that of delta connected motor.
RE: Star delta winding selection for motors
In dual voltage IEC motors, the Star windings are generally for connection to the higher voltage, the Delta windings are for connection to a lower voltage, specifically a voltage that is lower by a factor of 1.732 (√3). So for instance, 380 / 220V or 415 / 240V. Of this type, there are two sub-groups: dual voltage only, and dual voltage Star-Delta start, which has 12 leads.
Neither version intended to be operated in any other manner. Some people make claims that connecting them in the opposite pattern will save energy, but while technically true, they leave out the fact that doing so can have serious ramifications regarding the motor and load profile, most of which will lead to the early demise of the motor.
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RE: Star delta winding selection for motors
Bill
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"Why not the best?"
Jimmy Carter
RE: Star delta winding selection for motors
Mr,Mnewman already explained that delta conneted winding of same motor will produce more torque than star connected winding. A six lead motor can be connected in either way, subject to aqueuate cooling options done by the manufacturer
RE: Star delta winding selection for motors
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Star delta winding selection for motors
If the motor is designed to be connected in delta at line voltage, connection in star at that line voltage considerably reduces the effective rating of that motor.(Down to 1 third rating)
If the motor is designed to be connected in star at line voltage, connection in delta at line voltage will overflux the iron and the motor will fail.
Best regards,
Mark Empson
L M Photonics Ltd
RE: Star delta winding selection for motors
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Star delta winding selection for motors
As per your post , we can rule out the possibility of changing star designed motor to delta.But we can change a delta designed motor to star connection ,with reduced output.
RE: Star delta winding selection for motors
I was wondering, at a time like this when the operator has made the pulper too thick if we could rewire the motor in Star? It is delta connected at 420V feed. Would this at least get the motor turning so more water can be added and maybe pumped out. The pump inlet is behind and extraction plate and will not pump unless the Agitator is running.
Will rewiring the motor cause damage. This probably seems like a stupid question to most coming from an elect tech.
Thanks for your time.
RE: Star delta winding selection for motors
RE: Star delta winding selection for motors
A variable speed drive would allow you to develop full torque from standstill but will be fairly pricey at that size, in the order of £6k or so for the bare drive.
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If we learn from our mistakes I'm getting a great education!
RE: Star delta winding selection for motors
If you wire the motor in star, you will get one third of the full voltage torque out of the motor. This is probably less than the torque being developed by the motor with the soft starter unless the start current is very restricted.
Can you give an indication of the type of soft start profile being used (i.e. current limit, voltage ramp etc) and what the maximum current that the soft starter is allowing is. This will give us a better idea what is actually happening and then perhaps we can help from there.
ScottyUK
Not necessarily true. Many VFDs struggle to produce full torque at zero shaft speed due to insufficient flux in the iron.Closed loop vector will do this and the DTC drives will also do this, but most sensorless vector drives only reach full torque etc at frequencies between 3Hz and 10Hz depending on the design. A bigger drive does not help.
Best regards,
Mark Empson
L M Photonics Ltd
RE: Star delta winding selection for motors
RE: Star delta winding selection for motors
Laziness on my part for not being more specific; yes, I agree with you.
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If we learn from our mistakes I'm getting a great education!
RE: Star delta winding selection for motors
It's hard suggesting that there maybe a better way than their recent 10k project!
P.S The softstart is an ABB type. I noticed whilst quickly scanning through the parameters that their is a kick start option and an initial start voltage. Is anyone familiar with these?