Is it IEC (CE) requirement to provide assisted start to 3 ph induction motor above certain size?

[PaulBr]

Hello guy:
Does anyone know answer to question in subject line? If it is indeed requirement, can relevant documents to be sited? Motor in question is regular 3 phase squirrel cage induction motor. If this is just good practice in IEC world, then when (motor size) it needs to be used?

Best regards,

PaulBr

 

[ScottyUK]

On a sufficiently stiff system it's not unusual to have LV (400V) motors of 200kW - 250kW started direct-on-line. Motors this size require a large transformer of > 2000kVA to keep the voltage dip tolerable, and in my opinion motors greater than 200kW really should be on the MV system. I've heard of a few LV (690V) motors of 300kW+ being started DOL (with a suitably large transformer) but haven't actually seen one that large first hand.

There's nothing I'm aware of in the standards which mandates use of assisted starts for large motors, and any decision to do so which would come from sound engineering practice.

 

[jraef]

By assisted starting I suppose you mean having a smaller motor used to accelerate the larger motor to some level before attempting to start the large one? Not that it matters because as ScottyUK says, there is no standard I am aware of requiring this, it's an engineering decision. Generally it's done when the mass is so large that the accelerating time at maximum torque will cause heating that will exceed the thermal damage curve of the motor. That is totally subjective.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[PaulBr]

I apologize for not being clear. I was using terminology that our customer was using. By assisted start they mean use of a) delta - wye contactor arrangement; b)soft start; or c)VFD. Motor in question is 3 phase, 50Hz,400VAC, 45kW motor. Customer is located not in EU but is trying to follow IEC standards.
We have searched internet and could not find any hints that such regulations exists. Only one paper was saying that if motor is class IE2 efficiency it needs to be using with VSD. Nothing was saying about "assisted start"

PaulBr.

 

[LionelHutz]

The power company would be the one who might have requirements on that.

 

[waross]

I agree with Lionel.
Many utilities limit the size of motors started DOL to minimize system voltage dips for other customers.

Bill
--------------------
"Why not the best?"
Jimmy Carter