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Which of the following statements are correct for synchronous motors? 1. Synchronous motors are well-suited for direct connection top reciprocating compressors. 2. Over-excited synchronous motors are most commonly used for power factor improvement. 3. Synchronous motors are generally used for current regulation of long transmission lines Select the correct answer using the code given below.
Following statements are given for DC motors (a) DC motors require less maintenance than AC motors (b) DC motors cannot provide high starting torque (c) DC motors are not suitable for very high-speed applications (d) The methods of speed control of DC motors are simpler and less expensive than those of AC motors Which of the following statements are correct?
Consider the following statements regarding ac drives: 1. For the same kW rating, ac motors are 20% to 40% light weight as compared to dc motors. 2. The ac motors are more expensive as compared to same kW rating dc motors. 3. The ac motors have low maintenance as compared to dc motors. Which of the above statements are correct?
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
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?
Which are the corrections applied to the hydrometer readings? (i) Meniscus correction (ii) Temperature correction (iii) Density correction (iv) Dispersing agent correction 
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 three-phase cylindrical rotor synchronous generator has a synchronous reactance Xs and a negligible armature resistance. The magnitude of per phase terminal voltage is VA and the magnitude of per phase induced emf is EA. Considering the following two statements, P and Q, P: For any three-phase balanced leading load connected across the terminals of this synchronous generator, VA is always more than EA Q: For any three-phase balanced lagging load connected across the terminals of this synchronous generator, VA is always less than EA Which of the following options is correct?
Which of the following statements are true? a. As load increases armature current decreases, regardless of excitation. b. For under and over excited motors, power factor tends to approach zero with increase in load c. With normal excitation when load is increased, change in armature current is greater than in power factor which tends to become increasingly leading. d. Both with under and over excitation, change in power factor is greater than in armature current with increase in load.
A synchronous motor absorbing 60 kW is connected in parallel with an continuous load of 240 kW operating at 0.8 power factor lag.What is the kVAR supplied by the synchronous motor to obtain a total power factor of 0.9 lagging?