How to calculate drive over load current and kW

E

Thread Starter

Edwin

We have a 7.5kW drive which rated amps is 16 Amps and the Rated Continuous Current in High Overload is 12 Amps and the Power rating in kW (10% overload) @380 V Supply is 7.5 kW and in 50% 5.5kW.

Can any one explain how to calculate the same and the technical description for the same.
 
From my reading of your post, you want to learn how to compute the ratings. Here are the equations.

To compute the rated power at full load amps
P(power in W) = I(current in A) * V(voltage in V) * (power factor)

Rated amps = 16 A
Voltage = 380 V
We can assume power factor = 1 for now.

In 3 phase system you will multiply one of the single phase power by sqrt(3). This is only a mathematical derivation of phasors and analysis of 3 dimensional diagrams of resultant power.

P = (sqrt(3) * 380 V) * 12 A * 1 = 7888.8 W = 7.8888 kW // We can round down to 7.5 kW

P(10%) = (8.414 kW)(90%) = 7.5726 kW // We can round down to 7.5 kW
P(50%) = (8.414 kW)(50%) = 4.21 kW // This rating does not equal the nameplate value, 5.5 kW.

I think I am missing information or I read the question incorrectly. Can you clarify where you extracted each number?

Also, please note equipment that is rated continuous current is usually designed with a factor greater than 1 by manufacturers. This factor depends on the electric code of each country.
 
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