VFD Modelling

Question 1

Formula for power absorbed by motor?

Answer 1

Motor output /efficiency

Question 2

Motor kvar is influenced by?

Answer 2

Motor Power factor

Question 3

Output Power of the VFD should be higher or lower than input power of motor?

Answer 3

Higher

Question 4

Power factor of VFD should lesser or higher Than power factor of motor?

Answer 4

Lesser (so that reactive power demand of motor can be met by VFD)

Question 5

How to adjust power factor of VFD

Answer 5

By adjusting ova of VFD

Question 6

VFD will draw reactive power from Source or not

Answer 6

Not because VFD input PF maintained at 100% (1)

Question 7

Advantages of VFD

Answer 7

1) Does not absorb reactive power from grid by thus input PF is maintained at unity
2) Does not inject short circuit fault current upstream into grid
3) speed control

Question 8

Disadvantage of VFD

Answer 8

Harmonics

Question 9

If load is need to be run at full speed 100% at continuous mode what starter is to be used?

Answer 9

Direct online starter

Question 10

If the motor has speed variations then which starter has to be used?

Answer 10

Variable frequency drive