Question

We have to calculate the value of Power of an electric DC motor IN WATTS made from scratch. The only known values that we have are: The Voltage (V) which is 9V and the current (I) that we are using which is 3 A, also the value of "n" which is n= 90.16 m (the number of turns of the wire used in the motor)

I already asked here for this problem and someone answered this:

Voltage = 9 V, current = 3 A, number of turns = n = 90.16

Power of motor = n*V*I = 90.16*9*3=2434.32 Watt

But I don’t think this is correct since the motor has power in and power out. Can someone else help? Thank you!

Answer 1

Hello!

you are absolutely right in the fact that there are two types of power while considering a DC motor!

P_in and P_out.

while efficiency can be calculated as

The formula to calculate Power _input is easier and is as follows

Pin = Voltage(v) Current (I)  

In youre case, V = 9v and current I = 3 A

you can neglect the number of turns in coil as this is a DC motor So the total input power supplied to the DC motor = 27 Watts!

The motor might be rated to handle 2400 Watts + (then number of turns of coil can be considered) but at a voltage of 9 volts and drawing a current of 3 Amps, it is definitely not drawing 2400 Watts of input power!

Now considering Output power, it is mandatory to know some other parameters such as the speed of the motor ( in rpm)

P _out = T , where, T= torque (force in newtons times the radius)

and = angular velocity which is calculated as   

Only then the Out put power can be measured!

Hope I have helped you! Please leave a rating if you liked my answer :)