Answer / rvg

Variable frequency devises not making use of any
contactors, since the speed and rotation reverse can be
done with the circuit itself.
VFD having control of supply frequnecy and speed can be
changed with that.

Answer / revansiddappa p.h.

Basically contactor is used to make and break the circuit
like any switch. For handling higher current and volatge we
use contactor; not only for motors.
Between VFD and motor; contactor is not required.
Because VFD will have features like enable and disable.
VFD will use IGBT's inside for switching application.
As IGBT's are semiconductor ; switching is fast compared
to electromachanical type contactor.And IGBT's handles
larger currnts.By enabling or desabling of VFD we can
Start/stop motor(with speed command). If contactor is used
there will be some time difference in swithcing ON/OFF of
IGBT and contactor which may lead to failure of IGBT and
motor winding and insulation. So it is meaning less to use
conatctor and also cost will be more.

Answer / nandan d shanbhag

Due to electromechanical bouncing of the contactor
contacts , voltage spikes are generated which in turn will
result in failure of smiconductors in the drive. However
due to eletrical regulaton if contactor needs to be
provided for electrical isolation then there must be delay
of 1 sec before starting the inverter after contactor is on
and contactor should be made of atleast .5 second after the
inverter is made off.

Answer / shailesh

vfd is a variable frequency drive,which not provided
contactor because there use a thyristor.

Answer / jayaseelan

This will cause unnecessary wear on the contactor and
there will always be a slight delay while the inverter
initialises.ie.if contactor placed in between vfd and motor
response time of contactor gettting on is slow compare to
vfd response speed so return current wii affect the
electronic bords.thats y contactors not not used in output
of vfd.

Answer / jayaseelan

This will cause unnecessary wear on the contactor and
there will always be a slight delay while the inverter
initialises.

what is the difference between UPS & Inverter

7 Answers   HAL,

What are the types of piano switches?

0 Answers  

ASTM D 3455 - Standard Test Methods for Compatibility of Construction Material with Electrical Insulating Oil of Petroleum Origin has been used for Testing Transformer Oils with a product placed in it. Aged Control Oil has a Power Factor of 0.032% at 100°C. Aged Oil with a Test component has a Power Factor of 0.093% at 100°. Is this increase acceptable? If not why? How much increase is acceptable?

0 Answers  

Why the generator rating in kva

32 Answers   CompuCom, DLF, Genpact, HNG, SIPM,

The ripple frequency in output of fullwave bridge rectifier is a. Half the input b. Twice the input c. Same as input

0 Answers  

Whether the vacuum contactor requires Short circuit protection?If No,why?

0 Answers   Reliance,

Explain cos(theta) and Sin(theta)

0 Answers  

Sir, I have applied for the of Jr.engineer(Electrical & Electronics) & ASST. LOCO PILOT at ALL RRB BOARDS. please send me all RRB Boards solved papers in the year of 2001 tO till date. i requested send me the papers to my id as soon as possible (jet_0991@yahoo.com). (This is very urgent) Thank You,

0 Answers  

why dc supply is not applied for step up or down in transformer

3 Answers  

choose the non-switch device (A) transformer (B) diode (C) transistor (D) IC

3 Answers  

How to calculate cable size in sq units based on motor rating is KW

2 Answers  

What is induction motor

1 Answers   Indoco Remedies,