An over-excited synchronous motor takes

In case of synchronous motor, which of the following are true? a. Synchronous motor is not self-starting b. If the rotor poles are excited by field current and the stator terminals are connected to AC supply, motor vibrates. c. Variable frequency supply is used to start synchronous motor. d. By using frequency converter, a synchronous motor can be brought from standstill to its desired speed.

A

Only a and b are true

B

Only b and c are true

C

All are true

D

None of the above

Consider the following statements regarding synchronous machines: 1. When a synchronous motor is over-excited, its back emf is greater than the supply voltage 2. When a synchronous motor is over-excited, its power factor is leading 3. Synchronous motor is used as capacitor where load is so large that construction of a static capacitor is impractical Which of these statements are correct?

A

1 and 2

B

1 and 3

C

2 and 3

D

1, 2 and 3

A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will

A

remain same

B

go down

C

improve

D

none of the above

For a power system having induction motor loads, an overexcited synchronous motor is also attached. The induction motor will now operate at __________

A

lagging

B

leading

C

reduced power factor

D

increased power factor

For a power system having induction motor loads, an overexcited synchronous motor is also attached. The induction motor will now operate at ________

A

lagging

B

leading

C

reduced power factor

D

increased power factor

Consider a system consisting of a synchronous generator working at a lagging power factor, a synchronous motor working at an overexcited condition and a directly grid-connected induction generator. Consider capacitive VAr to be a source and inductive VAr to be a sink of reactive power. Which one of the following statements is TRUE?

A

Synchronous motor and synchronous generator are sources and induction generator is a sink of reactive power.

B

Synchronous motor and induction generator are sources and synchronous generator is a sink of reactive power.

C

Synchronous motor is a source and induction generator and synchronous generator are sinks of reactive power.

D

All are sources of reactive power.

For a power system having induction motor loads, an overexcited synchronous motor is also attached. Then the over all power factor __________

A

improves

B

degrades

C

becomes upf

D

remains same

For a power system having induction motor loads, an overexcited synchronous motor is also attached. Then the over all power factor?

A

improves

B

degrades

C

becomes upf

D

remains same

Which of the following will happen due to an overexcited synchronous motor?

A

The machine draws a leading power factor current.

B

The machine supplies a leading power factor current

C

The machine draws a lagging power factor current

D

The machine supplies a lagging power factor current.

For an overexcited 3 phase synchronous motor, connected to infinite bus is __________

A

motor is delivering reactive power to IBB

B

motor is absorbing reactive power to IBB

C

motor is delivering zero reactive power to IBB

D

none of the mentioned

An over-excited synchronous motor takes

Related Questions