Answer / r. anand

VFD(Variable frequency Drive) is a type of AC Drive.
There are two types of AC Drives of this category,
VVD (Variable Voltage Drive)in which the speed of the drive
can be controlled by varying the voltage input to the drive.
and
VFD (Variable Frequency Drive)in which the speed of the
drive can be controlled by varying the input frequency to
the drive.

Answer / mr. vinayak manohar hawal

AC drives control the speed of either an induction
motor or a synchronous motor by adjusting the frequency of
the power supplied to the motor.
AC drives are also known as adjustable speed drives
(ASD) or adjustable frequency drives (AFD) or variable
frequency drives (VFD) or variable speed drives (VSD) or
frequency converters (FC).
So I think that VFD is basicaly a method of AC drive
used for changing the speed of motor.

Answer / vikramsenareddy

both are same

Answer / comil83

Both are same.Now a days most of company like
siemens,ABB,yaskawa..etc provides diffrent types of control
in drives like 1) v/f control with feedback 2) v/f control
without feedback 3) vector control with and without
feedback.
In v/f control u can varying speed with the help of v and f
but u can not control torque and in Vector control u can
control speed as well as torque.

Answer / gautam himmatramka

But generally the concept of drives is that the ratio of
Voltage to freq. should be constant at each instant of
operation of drives. So i feel AC drives are a genral term
with VFD as a more specific name of the same.

Answer / sennapparajan

Both are same. comman name in Ac drive. In that by logic we
can segregate Vfd(variable freq. drive) VVd(variable
voltage drive).

Answer / suresh pethe

AC drive --  Variable voltage
VFD --       Variable Freqency

Answer / prabhakar jha

in vfd controlled speed & current by variation of frequency.speed & current directly proportional of frequency ...

Answer / rajesh jagtap

Actually AC Drive means a controller which require
Alternating Current power source and VFD means controlling
drive by varing frequency.

Answer / prasad surendra naik

in VFD you can vary the speed according to flow hense power
is consumed acoordingly
in AC drvies the speed of the motor remains constant
whatever the speed you cant vary the speed.

Why does the power consumed is always constant even if a fan speed is altered?

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