Explanation: Net flux in a compound motor is determined by addition of shunt field flux and series field flux. Thus, for calculating effective flux, net field current is find out. If is the constant value given for shunt field, while If net takes the presence of series field also.

Explanation: As armature current increases, the back emf decreases similar to shunt motor. By the same time series field resistance carries more armature current producing more amount of flux which is inversely proportional speed.

Explanation: At higher values of current speed of the DC cumulative compound motor starts decreasing due to effect of series field flux, which is also seen in DC series motor. Thus series motor and DC cumulative motor follow same characteristics.

Explanation: A differentially compound motor has flux/pole φ = (φse – φf). It is seen that on over-load φ reduces sharply and so the motor acts like a series motor on no load. This is why the differential compound motor is not used in practice.

Explanation: Because of φse increasing with Ia, the speed of the compound motor falls much more sharply than the shunt motor. Therefore, the n – armature current characteristic of the compound motor lies above that of the shunt motor for Ia < Ia ( fl) and lies below for Ia > Ia ( fl).

Explanation: At start, speed of DC cumulative motor is more than the speed of shunt motor because of series characteristic effect. Because of φse increasing with Ia beyond full load current, the speed of the compound motor falls much more sharply than the shunt motor.

Explanation: Shunt motor speed though decreases by slight value as armature current increases, it is assumed to be constant. But series motor and cumulative motor speed decreases as armature current increases. Only differential motor flux reduces with increase in armature current thus, speed increases.

Explanation: DC cumulative compound motor is the addition of best of series and best of shunt field motor. For shunt type torque is proportional to armature current while in series motor torque is proportional to square of armature current.

Explanation: Starting from zero armature current the characteristic of cumulative motor lies above the series characteristic and shunt characteristic, because it is the sum of series and shunt characteristic.

Explanation: Due to strong series field, speed-torque characteristic lies above of shunt field characteristic but below of series field characteristic, as no-load speed is finite for cumulative compound motor, at armature current less than full load current.

Explanation: In differential compound motors flux will reduce as load is increased because series flux opposes shunt field flux. This will increase speed upon addition of load. Therefore, it has negative speed regulation means speed will increase due to increase in load.