Question

1-Which of the following sentences is wrong? (why)

a-) The difference between the speed of the rotating field and the rotor speed in the synchronous motor is zero,

b-) The difference between the synchronous motor and the asynchronous motor is that the rotor is fed with alternating current from the outside,

c-) Synchronous motor and asynchronous motor can be used as generators,

d-) Synchronous motor and foreign excited motor are similar.

2-Which of the following sentences is true? (why)

a-) Asynchronous motor secondary with ring works like an open transformer,

b-) In order to give a star delta to the asynchronous motor, the mains voltage must be one of the phase voltage of the motor,

c-) Overcurrent role is connected between the U-V, V-W and W-U windings before the motor, in order to be easy to protect in asynchronous motors,

d-) The speed of the rotor is equal to the synchronous speed in asynchronous motors with power less than 2.2 kW. In the big, it is low.

3-Which of the following is wrong? (why)

a-) The most common form of starting in ring asynchronous motors is star / delta starting,

b-) To change the direction of rotation of the asynchronous motor, it is enough to change the positions of the R and S phases,

c-) If the operating voltage of the motor's phase winding is suitable for the mains voltage, motors with a power less than 3 KW can be triangularly connected,

d-) Asynchronous motor can be made by changing the rotor of the asynchronous motor.

4-Which of the following is wrong? (why)

a-) Every electric machine can generate voltage,

b-) The highest voltage occurring in the rotor in a 6 pole, 60 Hz induction motor is when the rotor rotates at 1200 rpm.

c-) In the application, lever, pako, automatic, electronic star triangle switches are used,

d-) Stator iron losses are always higher than rotor iron losses in the asynchronous motor.

5-) Pako star triangle switch; (why)

a-) There are 3 connection screws, b-) 3 + 3 = 6 connectors, d-) There are 9 connectors, e-) 11 + 1 = 12

there are connection ends, e-) 6 + 1 = 7 connection ends.

6-) Time role is not used in which of the following? (why)

a-) Changing the direction of rotation,

b-) Starting asynchronous motor with ring,

c-) Asynchronous motors In resistance starting, d-) star-delta operation,

e-) asynchronous motors with reactance (coil) In decision making.

7-) Which of the following sentences contains wrong provisions? (why)

a-) voltage is induced in the rotor winding of the synchronous motor,

b-) voltage in the rotor of the asynchronous motor induced,

c-) the speed of the asynchronous motor depends on the number of poles,

d-) the rotating field in the asynchronous motor There is also a synchronous motor.

8-) 3 ohms are measured with an ohmmeter between the V-W ends of a star connected synchronous generator. according to the effective resistance of a phase; (why)

a-) 1.5 Ω, b-) 3 Ω, c-) 2.5 Ω, d-) 0.75 Ω, e-) 2.25 Ω our.

9-) Which of the following sentences makes the wrong judgment? (why)

a-) the voltage generating mechanism of synchronous generators is different from that of DA machines,

b-) synchronous rotor speed in the generator can be found as the speed of the asynchronous motor,

c-) squirrel cage asynchronous motor can be used as generator,

d-) synchronous machines have opposite emf in rotor it does not.

10- Capacitive operation with synchronous motor ……………………………… .. ………………… ...

a-) connecting capacitor to phase winding ends …………… .. is provided,

b-) rotating area of ​​rotor speed more than the number of revolutions ……………… .. it may be possible,

c-) the excitation current is too high may be possible with …………………,

d-) the speed and the excitation current lowering can be achieved with ……………………….,

e-) in the opposite direction of the rotating field direction of the rotor to the rotating field speed .............................. rotation can.

Answer 1

1.) b.) TheTdifference between Synchronous motor and asynchronous motor is that the rotor of synchronous motor are excited by DC source and not by AC source.

2.) b.) One of the necessary condition for an asynchronous motor to be started with a star delta starter is that the main voltage applied should be the equal to the phase voltage of the motor.

3.) c.) If the operating voltage of motor's phase winding is suitable for main voltage the it is clear that the motor is using a star delta starter and for that it is must that the initial connection should be star connected and not delta(triangular) connection. After the motor reachs 75%-80% then the connection is changed to delta.

4.) a.) No according to me all electrical machines does not generates voltages as there some machines (motor ) which performs the task of absorbing the voltages instead of generating.

5.) Don't have any idea.. sorry for the inconvenience..

6.) Don't have any idea... Sorry for the inconvenience..

7.) Don't have any idea sorry for the inconvenience...

8.) b.) In case of star connection there is no difference between measured resistance and effective resistance of a phase in an synchronous generator i.e. 3 ohm ( answer )

9.) a.) The voltage generating mechanism of a DC machine and that of an AC machines are same the difference comes in the use and application of that power generated.

10.) Don't have any idea..sorry for the inconvenience....