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Are some systems unsuited to a VSD?

Systems with a high static head are unsuited to the use of a VSD. Static head is a measure of the pressure needed to make a fluid flow. This is a constant pressure and is independent of motor speed. When a high motor speed is needed to overcome the static head, the motor speed is no longer proportional to the flow rate. A small reduction in motor speed could result in a large drop in flow and a big reduction in machine efficiency.
In applications where the motor load remains more or less constant, a VSD is unlikely to achieve a significant saving, as the opportunity to reduce power is diminished.
Will you be able to retrofit a VSD to an existing motor?
An existing AC induction motor will be compatible with the application of a VSD. The viability of retrofitting the VSD will depend on:
路 1. the cost
路 2. the space available
路 3. the suitability of the application to variable speed control
You should also consider the additional energy savings that could be achieved by replacing the existing motor with an equivalent energy-efficient motor.