Why is the speed of a motor inversely proportional to flux?

Flux control method It is already explained above that the speed of a dc motor is inversely proportional to the flux per pole. Thus by decreasing the flux, speed can be increased and vice versa. To control the flux, a rheostat is added in series with the field winding, as shown in the circuit diagram.

What is relationship between speed with back emf and flux of DC motor?

Back EMF in practice Back EMF is directly related to speed, so when the speed decreases, so does the induced back EMF. From the equation above, we can see that if there is less back EMF, the voltage (and, therefore, current) across the motor will increase.

Why speed varies inversely with field current?

As the motor turns faster, the armature current decreases. If the motor has no load or friction, the motor will speed up to the point that V=ωKg . Kg is proportional field current, so with no load or friction, motor speed varies inversely with field current.

When the speed of DC motor is increased back emf decreases and current drawn increases True or false true?

Explanation: In case of DC motor, the speed is proportional to the back emf (Ea ∝ N). So, with the increase in speed, the back emf also increases. Therefore, armature current is also decreased, in case of series motor, armature current is equal to the line or load current. 4.

Why is speed directly proportional back emf?

When the motor is spinning the back EMF has a much bigger influence on current than resistance and inductance. As the back EMF is generated from the rotor is moving through the magnetic field generated by the permanent magnets, the back EMF is directly proportional to the motor speed, and the motor voltage constant.

Why is the speed of DC shunt motor depends on back emf?

In the case of DC motors Speed ∝ Back emf(Eb)/flux(φ). The field winding is connected across the armature. The resistance offered by the field is constant so the current is constant. Therefore the speed of the DC shunt motor depends on the back EMF.

How does a separately excited dc motor work?

Separately excited dc motor has field coils similar to that of shunt wound dc motor. The name suggests the construction of this type of motor. Here, the field coil is energized from a separate DC voltage source and the armature coil is also energized from another source.

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 happens when speed of dc motor increases?

Complete answer: A DC motor is a device which converts electrical energy such as voltage and current into mechanical energy like speed. Thus, when the speed of the dc motor is increased, the armature current will decrease.

When the speed of dc motor is increases back emf?

So, the back emf is directly proportional to speed. Hence, when the speed of a DC shunt motor is increased, then the back emf of the motor will increase.