1. Output
Efficiency = ------------ x 100 Always as a
percentage
Input

2. An electric drive motor takes 48kW from
the supply and delivers 42kW out of a
gearbox into the load.
What is the efficiency of the machine ?
48kW = input power
42kW = output power
42000/48000 x 100
= 87.5% efficiency

3. If a similar machine took 56kW from the
supply and delivered energy to the load at
85% , what is the output of the unit ?
output power/ input power x 100 = efficiency
output power = efficiency x input power/100
output power = 85 x 56000/100
= 47600W or 47.6 kW