Motor starting frequency

[BRIS]

What is the meaning of the following in relation to pump starting:

Motors shall withstand at least:
 3 consecutive starts, at 80% Un, with load inertia according to IEC60034-12.

 

[eeprom]

This is partly a guess...

1 The motors should be able to withstand 3 consecutive starts. This requirement would be for larger motors. Many large motors are limited to 2 starts per hour. This is especially true if they have a high inertia load which would cause the motor to have an extended start time.

2. The 80% Un...I assume this refers to the minimum starting voltage of 80% of nameplate. That's a common minimum allowable starting voltage.

3. I'm not familiar with IEC standards.

 

[MikiBg]

IEC60034-12 specifies starting requirements for motors depending on their type(N,H,NY or HY). If you can specify type of your motor, which depends on number of poles, power and starting method (DOL or star-delta), I'll be more helpful.

 

[BRIS]

Thanks for the response. The specification is a design requirement relating to pumps which will be rated each at between 500 kW and 1 MW. ( I think it is premature to be specifying limits on motor start frequencies when the requirements for the pumps and motors have not yet been determined.)

I am asking mainly from interest - I have not seen the requirement "80% Un, with load inertia according to IEC60034-12" - before and searching through IEC60034 -12 did not enlighten me at all.

 

[MikiBg]

Ok. For each motor type (think your will be N or NY if star-delta capable) that standard defines minimum torques, maximum locked rotor apparent power and number of starts (two starts from cold and one from hot are specified in general), and external inertia under which requirements shall be fulfilled. At least that's my understanding of it. When the time comes for more detailed data/questions, hope I'll be able to help.