How is flux produced in DC motor?

Magnetic flux in DC machine is produced by field coils carrying current. This is called excitation. Field winding is connected in parallel with armature winding.

What is flux in a DC motor?

When both the armature and the field windings are excited by a DC supply, current flows through the windings and a magnetic flux proportional to the current is produced. When the flux from the field interacts with the flux from the armature, it results in motion of the rotor.

Does DC current have flux?

DC FIELDS: The most common natural source of DC fields is the Earth which is essentially a large DC magnet, with magnetic lines of flux emanating from the South to the North Pole. Sometimes referred to as the geomagnetic field, this field provides a compass with the ability to indicate the direction of magnetic North.

Why is flux constant in DC shunt motor?

DC shunt motor is called a constant flux motor because flux depends upon the value of Ish and Ish =V/Rsh and both (V) and (Rsh) are constant therefore Ish is constant and hence flux remains constant. In dc shunt motor flux produced by field winding is proportional to field current Ish.

Which rule is applied to identify the direction of flux in DC motor?

Fleming’s right-hand rule gives which direction the current flows.

What is the purpose of Interpoles?

Interpoles. Interpoles are designed in DC motors to overcome the effects of the armature reactance and the self-induction of the machine. Most shunt and compound DC motors over one-half horsepower have interpoles located 90 electrical degrees from the main poles.

What will be the flux of dc motor when the motor is operating constant power mode at higher than base speed?

The reduction in flux will result in an increase in speed. Because of saturation of iron, the flux cannot be increased beyond its normal value. So the motor runs at a speed higher than normal speed. Hence field flux method is generally used constant power drive above the base speed.

Why is flux inversely proportional?

The total number of flux lines depends on the strength of the light source and is constant with increasing distance, where a greater density of flux lines (lines per unit area) means a stronger energy field. Thus the field intensity is inversely proportional to the square of the distance from the source.

Why a DC shunt motor is also called a constant flux motor or constant speed motor name any three applications of DC shunt motors?

In a shunt motor, the shunt field current Ish is always a constant since the field winding is connected in parallel to the armature winding and the supply voltage. If load change is not considered since a DC shunt motor has a constant flux φ and a constant supply voltage the speed of the motor remains constant.

Does the flux vary with the load in shunt DC motor?

In the shunt configuration, the armature and field voltages are the voltage of the supply. If the supply voltage is held constant, then it does not change with varying load. If the supply voltage is not held constant, it will vary due only to the voltage drop across the internal resistance of the supply.

What would happen if there was no flux in a motor?

The torque would have to change if the motor were going to change speed. If reducing the flux were going to increase the speed, then the torque would have to increase, at least temporarily. But if there were no flux, there could be no torque and the motor must slow down.

Why does DC current not produce magnetic flux?

DC current does product magnetic flux. In fact any charge motion will produce magnetic flux. But with DC, since the current is constant, the flux also remains constant. This is why it cannot be used in transformer, since a constant flux associated with secondary winding, won’t create any emf in the secondary.

How does flux affect the speed of a rotor?

In fact, physically, the rotor is moving because of field flux interacting with armature current’s flux. So physically if I reduce one flux, the speed must reduce, since I have reduced the cause of motion as Toque is also depended on Flux. (F=Bil)

Why can’t we use DC current in a transformer?

But with DC, since the current is constant, the flux also remains constant. This is why it cannot be used in transformer, since a constant flux associated with secondary winding, won’t create any emf in the secondary.