Answer / baikunth

generally there are two types of speed control systems are
available in induction motor. 1. scalar or VVVF and 2.
Vector or position control.In scalar control method we use
normal drives or cyclo-converters to control the voltage and
frequency for speed variation. but in vector mode we take
the feedback of position of the rotor and accordingly we
fire the device.It is the most complex technology and is
used only for precision speed control systems.

Answer / paddu241

frequency control

Answer / g senthilkumaran

Using scalar control, also called "volts per hertz" control
or v/f control, a drive essentially acts as a power supply
of a selected frequency and proportional voltage. At a
given speed, the motor performs much as it would when
supplied by utility power. For each frequency setting,
motor operation is governed by a torque Vs speed curve that
is similar to the torque Vs speed curve that governs
utility power operation.

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