My friend has
faced this
question! I
don't know
clearly. So
please anyone
give me the
correct and
short answer to
this question?
What is variable
frequency drive?
Types, what is
star to delta?
Why this

Answers were Sorted based on User's Feedback

Answer / vasu

VFD are used to make the motor to run in desired speed. By
variying the input supply frequency we can vary the speed of
the motor. some other types are VVFD - Variable voltage and
frequency drive, Vector drive.

Is This Answer Correct ?    4 Yes 0 No

Answer / rawjaw

We know a relation speed
say,N=120f/p,speed directly
proportional to freq.In some
applications large motors
used to drive a heavy load,we
start such motors from 0 rpm
& provides initial torque(say
160%) in order to achieve
energy efficient.ok..

Is This Answer Correct ?    4 Yes 2 No

Answer / hitesh kareliya

VFD Means Variable Frequency Drive,So that means we
controll the Pump's RPM via VFD in desired frequency.

Is This Answer Correct ?    1 Yes 0 No

Answer / amit shetkar

see firstly vfd is basically used mainly for 2 purpose i.e to
protect electrical motors & for speed control.
& now about that star delta arrangement it used before motor
in that star connection is used to give smooth start to motor
& when motor achieve it's speed so to maintain that speed
delta connection is used

Is This Answer Correct ?    0 Yes 0 No

Answer / vinay singh

When the elements are connected in neither series nor parallel
to reduce network star delta arrangement is used.

Is This Answer Correct ?    0 Yes 1 No

Post New Answer

More Instrumentation Interview Questions

Thermocouple is a transducer but rtd is not transducer why? Both taking heat as a input and giving mv

7 Answers  

How the flow can be measured by using DP Transmitter?

3 Answers  

What is the difference between a double acting and single acting positioner? what type of valves use single acting positioners?

1 Answers   NamPower, AquaTech, Samson Resources,

Definition of reverse and acting controllers:

0 Answers   Monnet,

what is the principle of ultrasonic flowmwter and radar type flowmeter?

4 Answers  

how u calculate ai/di/ao/do capacity in ur dcs?

1 Answers  

Why we use 4 to 20 mA, (This is International Standard) instaed of this can we use 4-16, or 4-24 or 3- 15 or any other range

13 Answers   ONGC,

tell me about the instrumentation,what is the actual need of it ?what are the characteristics of a IC engineer ?

11 Answers   L&T,

Can anybody tell me application of PLC,DCS,SCADA.

3 Answers   Reliance,

what is the difference b/w normal thermocouple and skin type thermocouple?

1 Answers   Heisco,

what is difference between E/P positioner and I/P positioner. Why E/P fixed in below actuator and why I/P fixed in other place

1 Answers  

Emergency Shutdown Systems/ Plant Shutdown System.

0 Answers   CCIE,

  • Civil Engineering Interview Questions Civil Engineering (4601)
  • Mechanical Engineering Interview Questions Mechanical Engineering (3694)
  • Electrical Engineering Interview Questions Electrical Engineering (15695)
  • Electronics Communications Interview Questions Electronics Communications (2631)
  • Chemical Engineering Interview Questions Chemical Engineering (746)
  • Aeronautical Engineering Interview Questions Aeronautical Engineering (78)
  • Bio Engineering Interview Questions Bio Engineering (30)
  • Metallurgy Interview Questions Metallurgy (95)
  • Industrial Engineering Interview Questions Industrial Engineering (198)
  • Instrumentation Interview Questions Instrumentation (2860)
  • Automobile Engineering Interview Questions Automobile Engineering (171)
  • Mechatronics Engineering Interview Questions Mechatronics Engineering (41)
  • Marine Engineering Interview Questions Marine Engineering (60)
  • Power Plant Engineering Interview Questions Power Plant Engineering (166)
  • Engineering AllOther Interview Questions Engineering AllOther (1330)