單項(xiàng)選擇題The main difference between a motor control circuit containing low voltage protection and low voltage release is that the latter contains ().

A.a magnetic operating coil
B.normally open line contacts
C.thermal-overload protection
D.a momentary-contact start button


您可能感興趣的試卷

你可能感興趣的試題

2.單項(xiàng)選擇題The part of a fuse that melts and opens the circuit is made of ().

A.copper and antimony
B.steel and babbitt
C.aluminum or beryllium alloy
D.zinc or an alloy of tin and lead

3.單項(xiàng)選擇題Time delayed or delayed action-type fuses are designed to ().

A.prevent grounds in branch circuits
B.prevent opens in motor circuits
C.permit momentary overloads without melting
D.guard lighting and electronic circuits

4.單項(xiàng)選擇題Which of the following statements is true concerning all three-phase alternators?()

A.Each has three separate but identical armature windings acted on by one system of rotating magnets
B.Each has one armature winding acted on by three identical but separate systems of rotating magnets
C.All three-phase alternators are designed to operate with a O8 leading power factor
D.The three phases always provide power to the load through three sets of slip rings and brushes

5.單項(xiàng)選擇題The function of damper windings in a synchronous motor is to ().

A.eliminate slippage
B.provide excitation
C.provide starting torque
D.increase efficiency

最新試題

Flame failure in an automatically fired auxiliary boiler can from a/an ()

題型:?jiǎn)雾?xiàng)選擇題

The cetane rating of diesel fuel is an indication of the ()

題型:?jiǎn)雾?xiàng)選擇題

For a given exhaust gas boiler, what is the quantity of its evaporation mainly determined?()

題型:?jiǎn)雾?xiàng)選擇題

Using a file without a handle may result in ()

題型:?jiǎn)雾?xiàng)選擇題

By comparing the exhaust gas temperature of each cylinder, the operator can determine if the load is balanced throughout the engine. The device most commonly used is a()

題型:?jiǎn)雾?xiàng)選擇題

Which of the diesel engine components listed increase air density and helps to improve engine operating efficiency?()

題型:?jiǎn)雾?xiàng)選擇題

()connectors hold best if a wire is accidentally pulled or a connection becomes loose.

題型:?jiǎn)雾?xiàng)選擇題

When does auxiliary burner of incinerator put into operation? ()Ⅰ. start incinerator when it is coldⅡ. the sludge for dealing with is littleⅢ. the sludge for dealing with is largeⅣ. the water and impurity in sludge are too muchⅤ. the temperature in incinerator is lowⅥ. dealing with little solid rubbish

題型:?jiǎn)雾?xiàng)選擇題

One of the reasons that cause oil flowed from sludge outlet of a self-cleaning separator is()

題型:?jiǎn)雾?xiàng)選擇題

If separating effect is not good, which measure should be taken ()

題型:?jiǎn)雾?xiàng)選擇題