When the value of back emf in A DC motor is maximum?

When the value of back emf in A DC motor is maximum?

So, we can say that the back emf in a DC motor will be maximum when the motor has picked the maximum speed. The correct option is (A). Note: When the motor starts at first the back emf is zero. Even if the motor gets full voltage and current flow, if the motor is not turning the back emf will be zero.

What is the back emf of A DC motor?

When the armature of the DC motor rotates under the influence of driving torque, the armature of the conductors moves through a magnetic field inducing an emf in them. The induced emf is in the opposite direction to the applied voltage and is known as the back emf.

What is the value of back emf at the instant of DC motor?

The coil of a DC motor is represented as a resistor in this schematic. The back emf is represented as a variable emf that opposes the one driving the motor. Back emf is zero when the motor is not turning, and it increases proportionally to the motor’s angular velocity.

What is the value of back emf?

Lenz’s Law applied to motor circuits Supply voltage = 195 V. Back EMF = -45 V.

What will happen if the back emf of a DC motor vanishes suddenly?

If back emf of a dc motor vanishes suddenly, motor circuit will try to retain back emf by drawing more current from supply. As the back emf vanishes zero, the whole supply voltage appears across armature and heavy current flows.

What will happen if the back emf of a dc motor vanishes suddenly?

What will happen if the back emf of dc motor?

2. What will happen if the back emf of a DC motor vanishes suddenly? Explanation: If back emf vanishes suddenly, motor circuit will try to retain back emf by drawing more current from supply. If supplying unit didn’t trip down by this time, excess current in armature may heat up the armature.

What is the effect of back emf in DC motor?

Back emf is very significant in the working of a dc motor. The presence of back emf makes the d.c. motor a self-regulating machine i.e., it makes the motor to draw as much armature current as is just sufficient to develop the torque required by the load.

When is the back emf of a DC motor maximum?

Back emf is proportional to the speed of the motor. Hence, it is maximum when the motor has picked up maximum speed. Was this answer helpful?

How does the magnitude of the back EMF decrease?

As the back emf depends on the current their value also decreases. The magnitude of the back EMF is nearly equal to the supply voltage. If the sudden load is applied to the motor, the motor becomes slow down. As the speed of the motor decreases, the magnitude of their back emf also falls down.

When does the maximum power develop in a DC motor?

By differentiating both side will respect to I a and equating it to zero, we get, Now we can see from the above equation that the maximum power develops in a DC motor, when the back EMF of the motor is exactly equal to the half of supply voltage.

How is mechanical energy induced in a DC motor?

The mechanical energy induced in the motor is the product of the back emf and the armature current, i.e., E b I a. 2. The back emf makes the DC motor self-regulating machine, i.e., the back emf develops the armature current according to the need of the motor.