When to rewind and when to replace
Five questions to ask before you send a burnt motor back to work.
IE2 or IE3: what the efficiency class means
What the labels mean in rupees for a motor that runs all day.
Every induction motor sold in India carries an efficiency class: IE1, IE2, IE3 or IE4. The higher the class, the more of the electricity it draws becomes useful work, and the less becomes heat.
The difference sounds small. A 15 kW, 4-pole motor might be about 91% efficient at IE2 and 92.5% at IE3. But a motor running 16 hours a day, 300 days a year, uses about 72,000 units. At ₹9 a unit, that 1.5% difference is worth around ₹10,000 a year, for a price difference that is often less than that.
The saving grows with running hours and with motor size. A pump motor that runs round the clock is the best candidate for IE3. A motor that runs twenty minutes a day is not worth replacing just for efficiency.
Efficiency also falls when a motor is badly oversized. A 30 kW motor driving a 12 kW load is less efficient than a 15 kW motor doing the same work. Before you replace a motor, check its actual load. Our free survey does this with a power analyser, so you know which motors to change first.
