I have a question.
We have a 50 hp motor running having rated current of 75 amps. This motor winding is connected in star and the starter used is a DOL starter(Direct 0nline). The motor is running at close to rated HP.

My question is if we now connect the motor winding in delta what will happen to
1) starting current
2) running current
3) starting and running torque
4) Will the mechnical load it is driving get affected.
5) Normally which is the configuration in which a motor needs to be connected during running.

Hope i am clear in my in what clarification i seek

 

>I have a question.
>We have a 50 hp motor running having
>rated current of 75 amps. This motor
>winding is connected in star and the
>starter used is a DOL starter(Direct
>0nline). The motor is running at close
>to rated HP.
>
>My question is if we now connect the
>motor winding in delta what will happen
>to
>1) starting current <

Will go up considerably

>2) running current <

As above

>3) starting and running torque <

Starting torque will go up but running torque should stay the same for same load

>4) Will the mechnical load it is
>driving get affected. <

Yes the additional starting torque will put extra stress

>5) Normally which is the configuration
>in which a motor needs to be connected
>during running. <

This depends on the voltage you shouldn't connect in delta unless it's designed for it.

Please give the system voltage Phase-phase Nameplate voltage.

Regards
Roy

 

Dear Thompson,

Starting current in case of delta will increase in this case. You may use an AC current measuring clamp meter to measure it.

Running current in delta configuration, you may easily find on the name plate of the motor. Similarly you may measure it as per actual in running condition.

Torque is related to current.

Mechanical stresses increase with increase in starting current.

Star or delta in running condition may be decided by you depending upon RPM you require during running operation as mentioned on the name plate.

If there are more mechanical stresses leading to frequent break down, then you must use soft starter for your application.