3ph motor starting
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Ed MacLaren
Senior Member
Re: 3ph motor starting
I'm not sure I understand your question.
Are you are referring to the operation of a Wye-Delta Starter (sketch below shows the power circuit only, the control circuit is not shown).
To use a motor with a wye-delta starter, it must have enough leads brought out so that the connection can be changed from wye to delta.
Also, the motor must be "delta-wound", that is, designed to operate with the three windings delta connected.
It is started (for a few seconds), with the windings wye connected. Each phase gets only 58% of rated voltage, and starting current (and torque) are lowered. The starter then re-connects the windings in delta for running.
This feature can be used to reduce the inrush current during starting.
If you are asking about the starting characteristics of a wye-wound motor versus a delta-wound motor, the starting characteristics of a motor are not determined by whether the motor stator is wye-wound or delta wound.
Induction motor starting characteristics are determined mostly by the rotor resistance.
Ed
I'm not sure I understand your question.
Are you are referring to the operation of a Wye-Delta Starter (sketch below shows the power circuit only, the control circuit is not shown).
To use a motor with a wye-delta starter, it must have enough leads brought out so that the connection can be changed from wye to delta.
Also, the motor must be "delta-wound", that is, designed to operate with the three windings delta connected.
It is started (for a few seconds), with the windings wye connected. Each phase gets only 58% of rated voltage, and starting current (and torque) are lowered. The starter then re-connects the windings in delta for running.
This feature can be used to reduce the inrush current during starting.
If you are asking about the starting characteristics of a wye-wound motor versus a delta-wound motor, the starting characteristics of a motor are not determined by whether the motor stator is wye-wound or delta wound.
Induction motor starting characteristics are determined mostly by the rotor resistance.
Ed
Re: 3ph motor starting
Also referred to as star-delta, probably the least complicated way to achieve reduced voltage starting. It requires a six lead motor that has the capability for the windings to be connected in either a wye are delta. The wye delta start connects the motor in a wye (star) configuration to start and, after a timing period, reconnects the winding into a delta. This change from wye to delta can be either an open or closed transition with the closed transition starter being the more expensive starter. The open transition causes a line disturbance in the form of a voltage and current spike which may or may not be a problem while a closed transition does not.
Starting torque of 33% of across the line starting which, again, may or may not be a problem but, never the less, should be considered.
Also referred to as star-delta, probably the least complicated way to achieve reduced voltage starting. It requires a six lead motor that has the capability for the windings to be connected in either a wye are delta. The wye delta start connects the motor in a wye (star) configuration to start and, after a timing period, reconnects the winding into a delta. This change from wye to delta can be either an open or closed transition with the closed transition starter being the more expensive starter. The open transition causes a line disturbance in the form of a voltage and current spike which may or may not be a problem while a closed transition does not.
Starting torque of 33% of across the line starting which, again, may or may not be a problem but, never the less, should be considered.
Re: 3ph motor starting
KSW
When you start a motor across the line it will draw about 6 times its full load amps. If the motor is large, this may cause the OD device to trip and voltage to drop significantly. The motor starter reduces the starting current to some value that you can live with.
KSW
When you start a motor across the line it will draw about 6 times its full load amps. If the motor is large, this may cause the OD device to trip and voltage to drop significantly. The motor starter reduces the starting current to some value that you can live with.
G
Guest
Guest
Re: 3ph motor starting
in my many years experience in a motor shop my old memory tels me that a delta connected motor of equal horsepower to a y connected motor will draw more(about 15% more) on inrush than y connected. That is one reason why larger motors which are mostly all delta connected are started using y delta starters to reduce inrush currents upon startup.
in my many years experience in a motor shop my old memory tels me that a delta connected motor of equal horsepower to a y connected motor will draw more(about 15% more) on inrush than y connected. That is one reason why larger motors which are mostly all delta connected are started using y delta starters to reduce inrush currents upon startup.
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