Answer / raghavendran

Drives can be classified as:

* Constant voltage
* Constant current
* Cycloconverter

In a constant voltage converter, the intermediate DC link
voltage remains approximately constant during each output
cycle. In constant current drives, a large inductor is
placed between the input rectifier and the output bridge, so
the current delivered is nearly constant. A cycloconverter
has no input rectifier or DC link and instead connects each
output terminal to the appropriate input phase.

The most common type of packaged VF drive is the
constant-voltage type, using pulse width modulation to
control both the frequency and effective voltage applied to
the motor load.

Answer / sandeep vazhoor

VVVF drives are generally classified into three types based
on the type of control philosophy adopted for motor control :
Ø Scalar control/PWM control
Ø Sensor-less vector control
Ø Vector control (with sensor) or Flux vector control

For flux vector control pulse encoder (or PG) will be
mounted on motor shaft as a feedback element.

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