quiz 6 1) (4pts) Explain the principle of operation of a three-phase synchronous

Question

quiz 6

1) (4pts) Explain the principle of operation of a three-phase synchronous motor.

2)      (2pts) Explain the differences between a three-phase synchronous generator and a three-phase
synchronous motor.

3) (4pts) Explain in detail all considerations that must be taken when starting a synchronous motor.

4) (2pts) List the two key advantages of a three-phase synchronous motor.

5) (2pts) Explain pull-in torque with its potential consequences and necessary control strategy.

6) (2pts) Explain pull-out torque and the negative consequences.

-----------------------------.--- ---_. _ ....

7)     (16pts) Use this nameplate data to answer the following questions about a three-phase synchronous
motor; 13.8kV, 160FLA, 1800RPM, O.85PF, 4000HP

a) How much apparent power is being delivered to the motor under fun load conditions?

b) How much true power is being delivered to the motor under fun load conditions?

c) How much reactive power is being delivered to the motor under full load conditions?

d) How much power is being delivered to the load under fun load conditions?

e) What is the efficiency of this motor?

f) How much torque is being delivered to the load under full load conditions?

g) Is the power factor of this motor most likely leading or lagging? Explain.

h) How much current would this motor draw from the line if it were adjusted for a unity power factor?

Explanation / Answer

1) operation:

Electrical motor in general is an electro-mechanical device that converts energy from electrical domain to mechanical domain. Based on the type of input we have classified it into single phase and 3 phase motors. Among 3 phase induction motors andsynchronous motors are more widely used.

When a 3 phase electric conductors are placed in a certain geometrical positions (In certain angle from one another) there is an electrical field generate. Now the rotating magnetic field rotates at a certain speed, that speed is called synchronous speed. Now if an electromagnet is present in this rotating magnetic field, the electromagnet is magnetically locked with this rotating magnetic field and rotates with same speed of rotating field. Synchronous motors is called so because the speed of the rotor of this motor is same as the rotating magnetic field. It is basically a fixed speed motor because it has only one speed, which is synchronous speed and therefore no intermediate speed is there or in other words it

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