Bharat Bijlee's SynchroVERT motor
Therefore, in applications when a motor of lower efficiency is retrofitted by a motor of increased efficiency, the input power may not reduce as much as anticipated when comparing the efficiencies of the two motors.
In some cases the input power of the energy efficient motor may actually increase compared to the motor of lower efficiency.
The user should be aware of the sensitivity of load and energy requirements to rated motor speed while replacing a standard motor with a higher efficiency class motor in a centrifugal pump or fan application.
One method is to use a VFD to reduce the speed to the original value, but this introduces the additional losses of the VFD, which may defeat the purpose of using an energy efficient motor, unless the customer is already using a VFD for energy savings on the pump.
If a belt and pulley system is being used, one can reduce the pulley diameter and bring down the speed of the pump.
If the pump is directly coupled to the motor, the only other alternative is to trim the impellor.
As thumb rule one could reduce the diameter (trim) of the impeller inversely to the increase in the speed, e.g. if the speed increases by 3%, then reduce the diameter of the impellor by 3%. This is valid for a trim of maximum 5%.
Instructions on how to calculate the amount of trimming are available on many internet sites. A simple search will give a lot of information. The pump manufacturer can be contacted for guidelines.
Bharat Bijlee has introduced SynchroVERT motors that conforms to the Super Premium IE4 class of efficiency, which have much higher efficiencies than IE2 or IE3. SynchroVERT was adjudged the ‘Most Innovative Energy Saving Product' of the year at CII's 17th National Award for Excellence in Energy Management 2016. Bharat Bijlee has also recently filed for a patent for the Line Start Permanent Magnet Synchronous Motor (LSPMSM) technology used in the design of SynchroVERT.
Authors:
Anil Naik, is Chairman of IEEMA's Rotating Machines Division and Ajay Bhalerao is Former Managing Committee Member of ERDA (Electrical Research and Development Association) and Former Member of the Standards Committee of BIS - ETD 15 & 22. Both are associated with Bharat Bijlee.
