更多"Starting motors，generators，and othe"的相关试题:
[单项选择]An advantage of DC motors over AC motors is that they （）
A. are less expensive
B. require less maintenance
C. can be started across the line
D. offer a more effective means of controlling speed
[单项选择]Complete maintenance of electrical motors should include periodic checks for machine （）
A. vibration
B. watertight integrity
C. speed droop
D. reactive power
[单项选择]Governors are equipped with motors for synchronizing, load sharing and frequency control（）
A. speed setting
B. load setting
C. speed changing
D. load changing
[单项选择]In most pumps and pump motors overpacking the ball bearings full of grease will result in （）
A. moisture emulsification of the bearing grease
B. insufficient circulation and overheating of the bearing
C. proper grease circulation to cool the bearing
D. sliding friction between balls and races
[单项选择]A spark arrestor（）.
A. keeps sparks from falling into an open tank
B. secures covers on ullage openings
C. prevents sparks from getting out of an engine's exhaust system
D. grounds static electricity
[单项选择]The operator of electrical motors should keep a constant check on the loads they carry because （）
A. low loads necessitate frequent insulation cleaning
B. exceeding nameplate values shortens useful life
C. energy is wasted if full loading is not utilized
D. power factor correction methods are load dependent
[单项选择]Which of the following electric motors would be the safest and most reliable to use on the main deck of a vessel in foul weather conditions?（）
A. Sealed motors
B. Drip proof motors
C. Enclosed motors
D. Watertight motors
[单项选择]Electrical failures in motors are caused by the breakdown of insulation, which may be caused by （）
A. penetration of moisture
B. accumulation of dirt
C. overheating
D. All of the above
[单项选择]What type of rotor is used in split-phase motors?（）
A. Dram
B. Salient pole
C. Squirrel-cage
D. Wound-rotor
[单项选择]Which of the motors for the devices listed below is fitted with an instantaneous overload relay?（）
A. Fan
B. Pump
C. Winch
D. Machine tool
[单项选择]Which of the following types of motors is often designed for use in correcting power factor?（）
A. Polyphase
B. Wound-rotor
C. Induction
D. Synchronous
[单项选择]Universal motors will operate on AC or DC current, and are generally found in （）
A. portable tools
B. large pump motors
C. turbo electric main motors
D. forced draft fans
[单项选择]Diesel engine electric starting motors generally require heavier duty motors and motors and operate at higher voltages than comparable starting motors for gasoline engines due to（）
A. higher speed required
B. flywheel-effect
C. lower starting temperatures
D. higher compression pressures
[单项选择]A dry-type spark arrestor removes sparks from a diesel engine exhaust by（）
A. increasing the linear velocity of the exhaust gases
B. changing directions of exhaust gas flow
C. decreasing the temperature of the exhaust gases
D. accelerating the exhaust gas through a reduced size orifice
