How many amps draw is there on a half hp 3 phase electric motor?

Answer 1

5 hp equals 3730 watts, and on a 3 phase 480 v system the line voltage is 277, so the current times 277 times 3 equals 3730. The answer in theory is 4.5 amps.

But you have to allow for 10% power-loss in the motor, and also the power factor, which could be 0.8.

Therefore the current is probably 6 to 6½ amps. Maybe 10 amps on starting up.

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The formula you are looking for when amperage is desired when horsepower is shown is - I = HP x 746 / 1.73 x volts x % efficiency x power factor.

A standard motor's efficiency between 5 to 100 HP is .84 to .91.

A standard motor's power factor between 10 to 100 HP is .86 to .92.

Amps = 5 x 746 = 3730/1.73 x 480 = 3730/830 x .84 x .84 = 3730/586 = 6.37 amps. Starting current will be 300% of the motors run current.

Answer 2

If you are asking about an actual motor it is best to read the motor's rating plate.

If you are asking how to figure out the current in Amps drawn by a motor which produces a power output of 3 horsepower (hp) this question is way too vague to be answered accurately without knowing a lot more technical details.

The current drawn will depend on (a) the type of motor and (b) the Voltage that the motor is designed to run on. Regarding motor type, is it a Direct Current motor or, if it is an Alternating Current motor, is it a single-phase motor or a 3-phase motor. If it is a single-phase motor, then is it a squirrel-cage induction motor or a commutator motor of the type often used in vacuum cleaners or power tools? Another type of alternating current motor is the slip-ring synchronous motor but that type is not often used to supply only 3 horsepower.

A very rough way to calculate a possible current draw if you know the motor's operating voltage is to use the fact that 1 hp is approximately equal to 0.75 kiloWatts. So 0.5 hp = 0.5 x 0.75 = 0.375 kW.

Now, knowing that the actual efficiency of a motor depends entirely upon its design type, we shall have to assume an efficiency factor for the conversion of electrical power to mechanical power.

If we assume the motor is only 50% efficient then, to produce 0.5 hp, it will have to be supplied with electrical power of at least 2 x 0.375 = 0.75 kW.

Since Power P (Watts) = V (Volts) x I (Current in Amps), the current drawn I would therefore be given by I= P/V:

At 12 Volts DC: 750 / 12 = 62.5 Amps.

At 120 Volts RMS AC: 750 / 120 = 6.25 Amps RMS single phase

At 240 Volts RMS AC: 750 / 240 = 3.125 Amps RMS single phase

Answer 3

The code book rating of a 1 HP motor at 115 volts is 16 amps. The same 1 HP motor at 230 volts is 8 amps. Where an amperage rating is needed for motor overload protection, always use the motor's nameplate rating as the exact current will be established by the manufacturer of the motor.

Answer 4

To answer this question the voltage of the motor needs to be known.

Answer 5

13.4 amps