Question 149Electricity/Electronics - QMED70% to pass
As shown in the illustrated electrically operated watertight door controller, how is the rotation direction of the door motor reversed? Illustration EL-0115
AI Explanation
The correct answer is B) reversing the direct current direction through the motor armature and maintaining the same direct current direction through the motor series field.
To reverse the rotation direction of a DC motor, you need to reverse the direction of the current flowing through the armature. By keeping the current direction through the series field the same, you maintain the same magnetic field, but the reversed armature current will cause the motor to spin in the opposite direction.
The other options are incorrect because: A) reversing both the armature and series field would result in the same rotation direction; C) reversing both would also not reverse the direction; and D) the shunt field is not involved in the basic reversing of a DC motor.
Related Questions
#147 By what means is the burning of controller contacts due to arcing, when opening, prevented? #148 As shown in figure "B" of the illustration, when the DC motor in figure "A" is operating at minimum speed what are the armature and field characteristics? Illustration EL-0153 #150 In the illustrated views of a lead-acid battery as shown in figures "A" and "B", what battery component has the sole function of preventing the individual plates in the negative plate group from coming into direct contact with the individual plates in the positive plate group? Illustration EL-0031 #151 How many cells are within a 24 volt lead-acid battery? #152 The nominal open-circuit voltage of one cell of a fully charged lead-acid battery is approximately how many volts?