What would happen if a series resistance is inserted in the field circuit of a DC shunt motor at a constant supply voltage?

For a constant supply voltage, what are the effects of inserting a series resistance in the field circuit of a dc shunt motor, on its speed and torque? (a) Speed will decrease and the torque will decrease.

What would happen if a series resistance is inserted in the field circuit of a DC?

In DC series motor, with increase in resistance of armature circuit increases the voltage drop in armature circuit and series field increases and therefore back emf decreases. Hence speed of DC series motor will reduce by inserting resistance in the armature circuit.

What would happen if a series resistance is inserted in the field?

If a resistance is added in series with field winding of d.c. shunt motor, then its speed increases, torque decreases.

Does resistance affect motor speed?

As we increase the armature Resistance, the drop across armature increases, which cause in decrease in the speed. As we add external Resistance in Rotor, the field current will decrease which causes decrease in Flux per pole (phi) , hence speed of the motor increases.

How speed of the DC shunt motor can be increased?

How speed of the DC shunt motor can be increased? Decreasing armature current will help in increasing speed for DC shunt motor. Since load current is addition of armature current and field current we’ll get less armature current for more field current.

How speed is controlled for DC shunt motor?

Variation of field flux Ф (Field flux control): In the shunt motor, speed can be controlled by connecting a variable resistor Rc in series with the shunt field winding. In the diagram below resistor, Rc is called the shunt field regulator. Figure: (a) Speed control of a D.C. shunt motor by variation of field flux.

How does resistance affect motor?

The primary effect on a motor is unbalanced current. Unbalanced resistance can result in negative sequence currents, causing an increase in operating temperature leading to thermal degradation of the insulation. Worst case, it may result in single phasing.

Why the speed of a DC shunt motor decreases as the load increases?

Detailed Solution. DC shunt motor: In case of DC shunt motor, the flux per pole is considered to be constant, torque increases with the increase of load current. If the load current increases then the armature current also be increased and the speed slightly falls due to increase in voltage drop in armature.

What happens when resistance is added in series with the field coil of a DC shunt wound motor?

Adding more resistance in series with the field winding will increase the speed as it decreases the flux. In shunt motors, as field current is relatively very small, Ish2R loss is small. Therefore, this method is quite efficient.