Apurva Dave
Registered User
I have project its high rise building where the electrical designer provided motor contributions estimates with shirt circuit study for 240V single phase hvac motors. All combined hvac motors of all the units makes difference. Their is also elevator motors 50hp, 30hp at 208V three phase.
The electrical designer used 4x full load amps to estimate the motor contribution fault currents.
I am wondering where it says in any code or standard full load of 4x is okay and conservative approach? I search internet and found the following:
ANSI standard C37.010 offers guidance when calculating motor contribution for a group of LV motors if detailed motor data is not available. Assuming a motor contribution of four times rated full load current is acceptable. The standard arrived at this value by assuming that the motor contribution of 3,6 times rated current came 75% from induction motors and 4,8 times rated current from 25% synchronous motors…..
However I cannot find this in standard C37.010
or is it in any other code or standards?
The electrical designer used 4x full load amps to estimate the motor contribution fault currents.
I am wondering where it says in any code or standard full load of 4x is okay and conservative approach? I search internet and found the following:
ANSI standard C37.010 offers guidance when calculating motor contribution for a group of LV motors if detailed motor data is not available. Assuming a motor contribution of four times rated full load current is acceptable. The standard arrived at this value by assuming that the motor contribution of 3,6 times rated current came 75% from induction motors and 4,8 times rated current from 25% synchronous motors…..
However I cannot find this in standard C37.010
or is it in any other code or standards?