In a starter motor the field windings are wound around mcq is given below:
Q. In a starter motor the field windings are wound around
(a) armature (b) commutator
(c) brush (d) pole shoes
Ans: (d) pole shoes
To start the engine a heavy-duty motor is used which is designed for very high electrical overloads and generates very high torque. It consists of a drive pinion that meshes with a gear on the fl ywheel of engine, and an electrical control circuit to control the operation of the motor. The starter motor must have ability to crank a cold engine at sufficient speed to start it. So it must be operate for short time duration. Therefore, for more than one starting attempts motor should be given sufficient time gap to dissipate the heat.
The motor consists of field coils with pole shoes, armature and a housing/frame. Furthermore, it has brushes, bushings etc. The starter motor works on direct current (d.c.) electromagnetism and consists of magnetic pole shoes which are placed at opposite positions inside the motor frame. The magnetic pole shoes can be strong permanent magnets or can act as electromagnets using a field winding (field windings are wound arround pole shoes).
The armature is fixed on the motor drive shaft which consists of a number of wire conductor loops wound around laminated iron core. The commutator copper segments are insulated from each other surrounding the shaft.
Carbon brushes conduct the electrical supply through the commutator segments to the individual wire conductor loops. The design of a simple d.c. starter motor is shown in Fig.. When the current is supplied to armature and magnetic field is produced in each wire conductor loop. The magnetic force between the poles acts from north to south.
The magnetic field direction depends on the direction of flow of the current. The action of these two opposite magnetic fields/forces make the armature to rotate.
Then this rotational motion is transfered to flywheel (flywheel is fixed with crankshaft) of engine through armature spindle. As a result engine starts cranking.
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Q. The number of positive plates in a battery cell is
(a) one more than the negative plates
(b) one less than the negative plate
(c) two less than the negative plates
(d) two more than the negative plates
Q. The three units contained in a regulator for automobile d.c. generator are
(a) voltage regulator* current regulator and Zener diode
(b) voltage regulator, current regulator and temperature compensator
(c) voltage regulator, current regulator and cutout relay
(d) any three of the above
Q. The number of windings in the stator of an alternator is
(a) 1 (b) 2
(c) 3 (d) 4
Q. Continuity in the field windings can be tested with a
(a) multimeter (b) growler
(c) voltmeter (d) none of the above
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