1. D.C cumulative compound motor Speed decreases when the load in the motor increases.2. If the carbon brushes remain one-third the length, they should be replaced
3. DC cumulative compound motor runs at full load at its specified speed.
4. The cumulative compound dc motor is used for sharpening machines, punchpresses, elevators, conveyors and rolling mills.
5. To change the direction of rotation in the compound motor, if only the connection of the shunt field winding is changed then its properties will change along with changing the direction of rotation.
6. The dc motor which has characteristic properties of both series and shunt motor is called a cumulative compound motor.
7. 4 point starter is required for above normal speed control of compound motor.
8. Compound motor has two fields, series and shunt field.
9. If the differential Compound D.C. motor is run in the open series field then the motor will not run.
10. If the brushes are not on the magnetic neutral axix then there will be more sparking on the commutator.
11. If the dc shunt motor is running at low load and the field becomes open circuit, the speed of the motor will be very high.
12. Growler test is used to find short circuit in armature winding.
13. Short coils in armature in a dc machine can be detected by looking at the sparking on the brushes.
14. The unbalanced armature produces vibrations at a fixed speed.
15. Insulation resistance value will decrease due to moisture in the winding.