What could be the cause of the diconnection of the linear contactor on the tram?
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Correct answer
C. Short-circuit in the circuits of one of the engines.
Explanation
In the photo you can see a contactor under the floor of a tram. The line contactor may disconnect because of a short circuit in the circuits of one of the motors - answer C.
The line contactor connects the circuits of the traction motors to the power network. When a short circuit occurs in a motor circuit, the protection devices switch off the contactor to prevent a fire or more serious damage. The converter (answer A) supplies the auxiliary circuits, and the reverser (answer B) changes the direction of travel - a fault in them is not a typical cause of the line contactor disconnecting. When the contactor disconnects, you report the fault to the dispatcher. You do not try to repair the motor circuits yourself, because this creates a risk of electric shock.
Legal basis: Art. 3 para. 1 of the Road Traffic Act (Prawo o ruchu drogowym)