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HVACity - Why Drives

The very basics:

The most commonly used motor in HVAC installations today is the three-phase, asynchronous AC motor, which is both inexpensive and of very reliable construction. Ordinary asynchronous AC motors are designed to make the operating speed dependent on the frequency and the voltage connected to the motor. For example, the mains supply in most European countries is 400V 50Hz. This gives a four-poled asynchronous AC motor an approximate speed of 1500 rpm.

  A Drive or static frequency converter is an electronic unit which provides infinitely variable control of the speed of three-phase AC motors by converting fixed mains voltage and frequency into variable quantities.

  While the basic operating principle of the drive remains the same, the product has undergone considerable development.  Frequency converters, which once featured thyristors, have been replaced by today’s microprocessor-controlled, digital units.