Approximate old motor efficiency (η) %:
This motor efficiency calculator allows you to calculate the efficiency of the AC 3-phase electric motor.Kindly enter the motor power rating, voltage, current, power factor and no of rewinds in any,into the calculator to calculate the motor efficiency.
Motor efficiency(%)= KW x 1000 x100- Z% volts x Amperes x power factor x 1.732
Please note that this calculator is provided for information purposes only and typically motor efficiency is specified on the OEM data sheet and shown on the motor name plate. However, this calculator is useful when no documents/name plate available for the motor and only the motor rating is available & an estimate of the efficiency is required.
This calculator will also give an indication of efficiency drop due to the multiple rewinds;
Each rewind normally reduces a motor’s efficiency by 1 – 3%, based on the number of rewinding already carried out, you may enter the total percentage of efficiency drop. When a motor fails the user has the normal choice between rewinding and replacement. The user should carefully consider the advantages of replacing the motor rather than having it rewound. In many cases the payback period is short when comparing a new motor versus rewinding. The additional cost of purchasing a new high efficiency motor when compared to the cost of the rewind can be recovered in energy savings typically within 1 year of continuous running.
