how do you calculate the horsepower on an electric motor if you don't know the efficency?

Question

i have a dc electric motor and it seems that to calculate the power, horse power, and current you need to know the efficency and to get the efficency you need to know the horse power (is there another way to do this)

Answer 1

You can get the power from the wattage (joules per second) =
voltage x current.
If you know the power going in, you can measure the power going out, the output power divided by the input power x 100 gives you the efficiency. Of course, if you don't know what current it draws, you can't do the calculation. All I can suggest is that you measure it.

Answer 2

You can easily measure the power in, which in watts is the product of the voltage and current in. What isn't quite as easy is the horsepower; for that you need a dynomometer. Once you've recorded the horsepower output for a range of input powers, convert horsepower to watts by multiplying by 745. The ratio of watts out to watts in is the efficiency. Most motors built nowadays should be in the 80 -90% efficiency range when new and operating around their design load.

Answer 3

Actually efficency is a simple ratio of power in/ power out. It has nothing to do with power consumption.
It looks to me like you are confusing units. Try writing all equations with all units listed and carried thru. Power itself is generally stated as watts which are readily converted to horsepower....

An old joke....How big is the horse??

Answer 4

Try to read all the small letter in the motor or if you have the specification read the specification, and find the actual current, and the actual voltage.

P = Voltage x current in watt

1 HP =745,699 watt

Answer 5

You can't. Even if you know the power going in, if you don't know how efficient that machine is using the supplied power you cannot know how much power (or horsepower) that is being put out.