CHAPTER. DC Motors. 8. Instructor Name: (Your Name ). Learning Objectives. List the components of a typical starting (cranking) motor Describe how interacting magnetic fields cause the armature in an electric motor to rotate
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Two magnetic fields that interact with each other combine to form a single magnetic field. If the arrows on the magnetic lines of force of both magnetic fields are pointing in the same direction, the resulting magnetic field is strengthened. If the arrows on the magnetic lines of force are pointing in opposite direction, the resulting magnetic field is weakened.
Figure 8-3(A) Current-carrying conductor placed in magnetic field causes an interaction between magnetic fields; conductor is compelled to move from strong magnetic field to weak field. (B) Current-carrying conductor formed into a loop is compelled to rotate around its axis to move from strong field to weak field.
Conductors that are carrying current are compelled (want) to move out of a stronger magnetic field into a weaker magnetic field.
Figure 8-4 Brushed DC motor; current flow through armature reverses directions every 180 degrees of rotation.
Figure 8-5 Magnetic field developed by pole shoes.
Figure 8-6 Armature windings and commutator segments.
Figure 8-8 Cutaway view of a starter motor.
Figure 8-11 Four insulated field coils with brushes.
Figure 8-12 Pole shoes and field coils installed in iron housing.
Figure 8-13 Interaction of magnetic fields results in armature rotation.
Figure 8-14 Series-wound motor.
Figure 8-15 Shunt-wound motor.
Figure 8-16 Compound motor.
Figure 8-17 Solenoid with coil not energized.
Figure 8-18 Solenoid with coil energized.
Figure 8-19 Shift-lever-type drive.
Roller clutch permits one-way drive.
Figure 8-22 Crank inhibit circuit.
Figure 8-23 Gear-reduction starter motor cutaway.
Figure 8-24 Measuring cranking circuit resistance by loading to 500A and measuring voltage drop on circuit.
Figure 8-25 Finding the source of the high cranking circuit resistance.
Figure 8-29 Diagnostic flowchart.
Figure 8-30 Cranking circuit diagram.
Figure 8-31 DMM measuring high and low side of magnetic switch coil during crank.
Figure 8-32 Voltage measurements at neutral start switch.
Starter no-load bench-test setup.
Figure 8-35 Testing for open field coils.
Testing for a shorted-to-ground field coil.
Figure 8-39 Testing armature for shorted-to-ground windings.
Figure 8-40 Testing armature for open circuits.
Figure 8-42 Energizing the starter motor solenoid to measure pinion gear clearance.
Figure 8-46 View looking into a single-loop armature.
Figure 8-47 Armature rotating due to magnetic field interactions and commutation.
Figure 8-48 CEMF with motor stationary (top) and motor rotating at full speed (bottom) and the effect on current drawn by the motor.
Figure 8-50 Starter solenoid hold-in and pull-in windings.