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Motors lvl 3

lesson 1 - synchronous motors

QuestionAnswer
1) The torque produced by a motor overload that pulls the rotor out of synchronization is referred to as ? torque. Pull out
2) When synchronous torque is at maximum, it is equal to the ? torque. Pull out
3) Synchronous motors are typically used for NEMA ? design applications. Class B
4) The two parts of the rotor of a synchronous motor are an induction-rotor (amortisseur winding) section and a ? section. Wound-rotor
5) The bearings for high-speed rotors are commonly mounted in endbells that are bolted to the motor. True
6) A ? may be used to start the rotor rotation and speed it up to almost synchronous speed. Pony motor
7) If a synchronous motor rotor slips out of synchronous speed for a period of time, ? are needed to shut it down. Protective relays
8) The rotor of a synchronous motor has only induction windings False
9) A(n) ? is a relay that removes the discharge resistor from the starting circuit of a synchronous motor and applies current to the DC field windings. Polarized field frequency relay (PFFR)
10) A common type of design for an out-of-step relay (OSR) is a current-type relay in series with the discharge resistor. True
11) Which of the following parts are included in the starting circuit for a synchronous motor? Control, Exciter, & Power
12) Depending on the motor design, an ammeter may read up to ? of full-load current at startup in locked rotor. 700%
13) The discharge resistor is wired into the ? circuit to provide a complete path for the current induced in the field windings. Exciter
14) The maximum torque required to accelerate a synchronous motor into synchronization at the rated voltage frequency is known as ? torque. Pull in
15) ? torque develops during transition as the motor speeds up to the synchronous speed from the maximum speed running as an induction motor. Pull in
16) Pull-out torque is the same as break-down torque of an induction motor. False
17) When a load is placed on the motor, the torque angle increases and the poles of the rotor begin to slip behind the stator and ? synchronous speed. Maintain
18) A ? power factor is the normal operating condition of a synchronous motor; although it is not the most efficient operating condition for the motor, it is the most efficient operating condition for the entire distribution system. Leading
19) A synchronous ? is a synchronous motor that provides power factor correction when operated at no load. Condenser
20) The current in the stator power circuit is at minimum level when a synchronous motor is at ? power factor. Unity
21) A motor-generator set is a motor and a generator with shafts connected used to convert one form of power to another form. True
22) Synchronous motors can be protected from damage caused by the loss of excitation in the DC winding by a(n) ? . Loss of excitation relay
23) A synchronous motor operating a blower is used to move air as well as correct the system power factor. The currents are plotted on the graph. A rotor current of less than 18 amperes results in an underexcited rotor. True
24) The illustration shows the starting circuit for a synchronous motor. Which component is used to discharge any AC potential that builds up in the rotor field windings? Discharge resistor
25) The illustration shows the starting circuit for a synchronous motor. Which component is used to apply current to the DC field windings and to remove the discharge resistor from the circuit? Polarized field frequency relay (PFFR)
26)The illustration shows the starting circuit for a synchronous motor. Which component is used to protect a motor when the rotor falls out of step with the rotating stator field? Out of step relay (OSR)
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