# What is the equation of back EMF in DC motor?

## What is the equation of back EMF in DC motor?

The current induces on the motor because of the main supply. The relation between the main supply, back emf and armature current is given as Eb = V – IaRa.

## What is the equation for emf in DC machine?

As the armature rotates, a voltage is generated in its coils. In the case of a generator, the emf of rotation is called the Generated emf or Armature emf and is denoted as Er = Eg. In the case of a motor, the emf of rotation is known as Back emf or Counter emf and represented as Er = Eb.

What is back emf and its equation?

Back EMF = -45 V. Net voltage across the motor, calculated according to Ohm’s Law (V = I x R = 10 A x 15 Ω), = 150 V.

What do you mean by back emf write the equation of back emf?

The equation to find out back emf in a DC motor is given below, The back emf Eb(= PΦZN/60 A) is always less than the applied voltage V, although this difference is small when the motor is running under normal conditions.

### What is emf equation described?

The EMF or electromotive force is the energy supplied by a battery or a cell per coulomb (Q) of charge passing through it. The magnitude of emf is equal to V (potential difference) across the cell terminals when there is no current flowing through the circuit. e = E/Q.

### How do you calculate the emf?

If we know the resulting energy and the amount of charge passing through the cell. It is the simplest way to calculate the EMF. The electromotive force of cell….The Formula for Calculating the EMF.

\varepsilon electromotive force
E the energy in the circuit
Q Charge of the circuit.

What is significance of back emf in DC motor?

Significance of Back EMF in DC Motor As the speed of the armature increases, the back emf also increases and causes the armature current is decrease. The motor will stop accelerating when the armature current is sufficient to develop the torque required by the load.

How do you calculate back EMF?

The back emf is calculated based on the difference between the supplied voltage and the loss from the current through the resistance. The power from each device is calculated from one of the power formulas based on the given information. The back emf is ϵi=ϵS−I(Rf+REa)=120V−(10A)(2.0Ω)=100V.

## How is emf formula derived?

Therefore, RMS value of emf per turn = Form factor X average emf per turn. Therefore, RMS value of emf per turn = 1.11 x 4f Φm = 4.44f Φm. This is called the emf equation of transformer, which shows, emf / number of turns is same for both primary and secondary winding.

## How do you calculate back EMF of a DC shunt motor?

For a DC motor, magnitude of the back emf is given by the same emf equation of a dc generator i.e. Eb = PɸNZ / 60A.

What is the significance of a back EMF?

The significance of Back EMF 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.