Starting Current 4100kW motor - IEC60034-12 1

[TriggeryDoo]

Hi,

For a pump package I'm procuring a 4100kW motor. My customer has not provided a starting current limitation in the specifications, and my motor supplier would like a number to be able to quote the motor most fit for purpose.

My customer has referred to IEC60034, however as far as I can see IEC60034-12 only gives values for calculating starting current for motors up to 1600kW. Any pointers as to where I could go for larger motors?

 

[ScottyUK]

Generally it is 'by agreement' between the motor manufacturer and the client because a motor of this size started DOL will have a significant effect upon all but the most robust distribution systems with a direct intake from the primary distribution system or the transmission system.

It is possible to design the motor to have a starting current less than 300% of FLC, but doing this will compromise many other aspects of performance which may (or may not) be significant in the specific application. Equally if the supply system is of limited capability then the application may have to adapt to suit the available supply.

You need to go back to your client and politiely insist that he provides sufficient information to provide a meaningful quotation.

 

[roydm]

Surely you would start a motor that size on some form of reduced Voltage or reduced frequency starter?

I'm used to grinding mill motors typically synchronous with a squirrel cage start winding and clutch.

 

[7anoter4]

According to Siemens AG Catalog D 84.1 / 2009 for IEC Version Motors for line operation
water cooled or air cooled of 3.3 to 6.6 kV 50 Hz 3750 to 4500 kW 2 to 6 poles the starting current is from 4.6 to 5.8 times rated current.

 

[ScottyUK]

11kV starter gear is expensive and less reliable than a circuit breaker, so if the system will stand it then DOL is the way to go. Obviously if the system isn't strong enough to cope then other methods would need to be used.

 

[7anoter4]

I agree with you Scotty. In my opinion, in order to preserve at least 95% voltage at transformer terminals in order to maintain the rest of consumers voltage in allowable limit when this motor starts D.O.L., the high voltage short-circuit apparent power has to be at least 800 MVA and the supply transformer at least 20 MVA rated.