Does replacing an existing motor for new a higher efficiency unit save energy?
Does replacing an existing motor for new a higher efficiency unit save energy?
Yes, but they offer a very long payback period in general, so must be looked at carefully.
The energy saved must be calculated properly, to ensure the client understands what return on investment they will gain. This is due to the fact new motors whilst more efficient are usually a few percent better. A policy of replacing with the highest efficiency rated motor on the market is a good one but replacing old motors just to save energy can be a flawed strategy depending on the age and condition of the existing motor.
It is possible that 20-year-old motors which were manufactured with lots of copper are actually just as efficient as the new modern motors; it is a myth to say that an old motor is always less efficient than a new motor.
That said consideration must be taken if the old model has been rewound once or more, as then there will be a guaranteed loss of efficiency, between 1 to 5%.
This is where the real savings are, putting in new high-efficiency electric motors when you replace old motors which have been repaired over the years. Again before and after trials are imperative on applications to ascertain exactly what savings can be achieved.
It is possible to get a good return on investment from an existing working motor that has been rewound previously, this can be checked whilst the motor is still in a working condition but if the motor has already failed then the potential savings can be calculated but not proven.
There are also alternative motor designs offering additional energy-saving up to IE4 /IE5 ratings, and smaller frame sizes are also available with different technology types, however you
need to consider the potential increased future repair costs when looking at synchronous motors and permanent magnet motors and both must be used with a VSD to run which if the Application cannot be run below 50hz may negate the savings of the upgrade.