Classification of motor:

 Below is the chart giving some more details of the motor and its efficiency:

 

Specifying an electric motor

When specigying what type of electric motor is needed, the mechanical power available at the shaft is used. This means that users can predict the torque and speed of the motor without having to know the mechanical losses assoicated with the motor. Example: 10 KW induction motor.

Power:

The power output of a rotary electric motor is:

P=

Where P is in horsepower, rpm is the shaft speed in revolutions per minute and T is the torque in foot pounds.

And for a linear motor.

P= F  v

Where P is the power in watts, and F is in Newtons and v is the speed in metres per second.

Efficiency:

To calcualate a motor’s efficiency, the mechanical output power is divided by the electrical input power

η=  ,  where  is energy conversion efficiency,  is elerical input power, and  is mechanical output power.

In simplest case = VI, and = , where V input voltage is, I is input current, T is output torque, and ω is output angular velocity. Ot is possible to derive analytically the point of maximum efficiency. It is typically at less than ½ the stall torque.