The significance is that it determines the operating state of a DC machine. A DC machine working as a motor will have its counter emf always less than the supply voltage. The difference would depend on amount of mechanical load tied to the motor. As a result, current would flow into the machine.
What is the use of back EMF?
Back EMF is important for DC motors . During starting , the back emf is zero and very large current flows through the motor (limited by armature resistance which itself is very small) , however as the motor picks up speed , the back emf opposes and limit the current to safe value.
What is no load speed of a motor?
Motor characteristics are frequently given as two points on this graph: The stall torque, , represents the point on the graph at which the torque is a maximum, but the shaft is not rotating. The no load speed, , is the maximum output speed of the motor (when no torque is applied to the output shaft).
What is the difference between load and torque?
When a motor is running in steady state, the armature current is constant, and the electrical torque is equal and opposite of the mechanical torque. When a motor is decelerating, the motor torque is less than the load torque. Conversely, when a motor is accelerating, the motor torque is higher than the load torque.
What is the back EMF?
The counter-electromotive force (abbreviated counter EMF, or CEMF), also known as the back electromotive force, is the voltage, or electromotive force, that pushes against the current which induces it. For example, the voltage drop across an inductor is due to the induced magnetic field inside the coil.