Power in kilowatts or KW is the relationship between current and voltage as measured at an electrical load. Current is stated in units of amps. KW is also referred to as applied power or "absorbed" power because it's the power actually used by the load. For example, power distribution companies deliver power in the form of kilovolts-amperes or KVA. However, due to inefficiencies in the load caused by the load power factor, only a percentage of this KVA is used. The amount used is in units of watts or kilowatts.
Determine the value of the amps, or "I," you are looking to convert. As an example, assume I is 40 amps.
Find a power supply that can provide the amps from step 1 to the electrical load. Connect the power supply to the electrical load. Also connect a voltmeter in parallel with the power supply and load so that you record voltage readings.
Power up the power supply to deliver the current I to the load. Note and record the voltage with the voltmeter. Call this value V. For example, assume you recorded V as 280 volts.
Calculate the power absorbed by the load in kilowatts or KW using the formula KW = V x I x 1.732. The 1.732 is the square root of 3, which accounts for the 3-phase part. Continuing with the example:
KW = 280 x 40 x 1.732 = 19,398 volt-amperes = 19.4 Kilowatts or 19.4 KW