采用交流传令钟的船舶,为满足驾驶台传令功能,要用( )。
A. 一套(两台)自整角机
B. 两套(四台)自整角机
C. 一套(两台)执行电机
D. 两套(四台)执行电机
三相2极异步电动机接在50Hz的电源上,若额定转差率sN=0.04,则该异步电动机的额定转子转速为( )。
A. 3000 r/min
B. 1000 r/min
C. 2880 r/min
D. 1440 r/min
( ) is the working grounding.
A. Grounding of potential transformers’ iron core
B. Grounding of current transformers’ iron core
C. Grounding of electrical welding machine
D. Grounding of transformers’iron core
For three-phase insulated power systems, in order to prevent the risk of personal electric shock, measures ( ) are generally adopted for necessary electrical equipment.
A. working grounding
B. protective grounding
C. protective neutral line connection
D. shield grounding