01․ For the same power output rating and full load speed, the motor will have poorest starting torque, is
In differential compund wound motor, since the series field oppose the shunt field, the resulant flux decrease with the increase in load. The decrease in flux with the increase in load cause the torque to be less than that of all types of DC motor.
02․ Drop in speed from no load to full load is very high in
Interpoles neutralize the cross magnetizing effect of armature and so sparkless commutation is obtained at different loads. Hence voltage drop in armature at full load is very small as compared to applied voltage (Armature reaction not considered). So drop in speed from no load to full load is very small shunt motor.
03․ For standing a DC motor a starter is required because
For protection of motor against the flow of excessive current during starting period, it is necessary to insert high resistance in series with the armature circuit.
04․ To get the speed of DC motor is more than normal without wastage of electrical energy _____________ is used.
The basic adjustable voltage armature control methode of speed control acommplished by means of an adjustable voltage generator is called ward-Leonard system. This system consists simply working the motor with a constant excitation and applying a variable voltage to its armature to provide the required speed. Very fine speed control over the whole range from zero to normal speed in both direction can obtained without any wastage of electrical energy from ward-Leonard system.
05․ The three point starter is used for
The three point starter is used for DC shunt and compound motor.
06․ The main disadvantage(s) of the ward-Leonard system is/are
As two extra machine are required, so arrangement is costly and maintenance is also costly. Low overall efficiency of the system at light load condition.
07․ Ward Leonard control is provides speed control
Ward Leonard speed control is provided in both direction. Actually the direction of rotation of motor armature can be reversed by reversing the direction of exciting current of generator with help of shunt regulator.
08․ Variation in speed by ward-Leonard control of DC motors occurs due to variation in
Ward Leonard system consist simply working the motor with a constant excitation and applying a variable voltage to its armature to provide the required speed. The variable voltage supply is obtained from a motor generator set.
09․ The armature voltage control is considered suitable for a DC motor driven at constant
Armature voltage control is best suited for constant torque system because the output delivered by the motor decrease with a decrease in applied voltage and a corresponding decrease in speed.
10․ Ratio of starting torque to full load torque is minimum in
In differential compound motor, series field opposes the shunt field. Hence ratio of starting torque to full load torque is minimum.