What happens when there is no back emf?

What happens when there is no back emf?

If there is no back end then large current flows in starting of motors because initial speed is zero and back emf is zero thus winding gets damaged for this purpose only we use starters for all motors. motor will not start. when the motor runs,there has to be back emf.

What is back emf explain?

Back EMF is the system in the coil of an electric motor that opposes the current flowing through the coil, when the armature rotates. Back EMF is the system in the coil of an electric motor that opposes the current flowing through the coil, when the armature rotates.

Why back emf is produced?

This back EMF is produced as a result of Lenz’s Law, which says that in a circuit with an induced EMF caused by a change in a magnetic field, the induced EMF causes a current to flow in the direction that opposes the change in flux. Note that the magnetic field lines begin to collapse as the flow of electricity slows.

What is the value of back emf?

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.

Is back EMF good or bad?

It’s kind of a good thing. Back EMF keeps current from going nuts. Pure resistance is kept low to keep heating down. After you’ve done that, you are relying on back EMF to keep your breakers un-popped and power components un-cratered.

What is the difference between EMF and back EMF?

EMF (or Electro Motive Force) is the voltage applied to the motor from an external power supply. Back EMF is the voltage produced within the motor windings which is opposite polarity but smaller than the applied voltage. Think of a motor as also being a generator.

Is back emf good or bad?

Why back emf is used in 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 does back EMF depend on?

The back EMF depends, of course, on the speed of the motor — the change in magnetic flux that generates it increases with motor speed — so that as the motor begins to turn, the back EMF grows until the motor has reached its maximum speed, at which point the back EMF stays at its maximum value.

Which dc motor is preferred for elevator?

DC cumulative compound motor having high starting torque up to 450% depending upon the degree of compounding. The speed regulation is varying up to 25 ~ 30%. That’s why these motors are used in elevators.

What is the difference between EMF and back emf?

How do you read back emf?

kubeek said: If you know your motor, then you know its internal resistance. You can measure the voltage and current apllied to the motor, and subtract the I*R from the voltage applied, and voila you get your back EMF.