Why should a series motor always be connected to a load?
Consider when starting a series motor the current flowing will be high, but the flux that the motor produces will be moderate since the series winding has less number of turns. If u start the motor without load the speed will increase. as speed increases the back emf increases.
Why a DC series motor should never run unloaded?
Thus from equation (2), it is clear that speed of DC Series Motor is inversely proportional to Armature Current Ia. … Therefore if the DC Series Motor is started at No Load then the speed of DC Series Motor will become dangerously high which will definitely damage the DC Series Motor.
What will happen to a DC series motor when its load is removed?
What occurs if the load is removed from an operating series DC motor? It will stop running. Speed will increase slightly.
Why does Series motor tend to race at no load and light loads?
According to speed equation, N α 1/Φ as Eb is almost constant. So on very light load or no load as flux is very small, the motor tries to run at dangerously high speed which may damage the motor mechanically.
Why a series motor is never started on load?
A series motor should never be started at no load. With no mechanical load on the series motor, the current is low, the counter-EMF produced by the field winding is weak, and so the armature must turn faster to produce sufficient counter-EMF to balance the supply voltage. The motor can be damaged by overspeed.
Which motor should not be started on no load?
Since speed is constant and torque (τ) is proportional to armature current (Ia). So that, starting a shunt motor at a heavy load requires a high starting current. In order to avoid this high starting current, shunt motors are not started at heavy loads and they should be started without any load.
What are the advantages of DC series motor?
Advantages of DC Series Motor
Dc series motor have good accelerating torque. Dc series motor have a relatively huge starting torques. Dc series motor delivers high torque during an overload. The dc series motor draws less current and power from the source compared to a shunt or compound motor.
Which DC motor is preferred for constant speed?
Explanation: Rotary compressor generally demand constant speed operation throughout the load. Sometimes, DC machines are not able to produce constant speed throughout the process hence, synchronous machine is used. 4.
What is the function of NVR coil in 4 point starter?
No volt release (NVR) – No Volt Coil in DC Motor:
In the DC circuit, NVR – No volt release is used to avoid the auto start of the DC motor when supply resumes.
Which motor has the poorest speed control?
1. Which of the following DC motor has the poorest speed control? Explanation: DC series motor at no load condition gives infinite speed ideally. Practically it will damage all the armature circuit.
What will happen if the back EMF in the motor absent?
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.
Which motor is preferred the most for traction purpose Why?
DC series motor is best suited for DC traction, cranes as it provides high starting torque and easy speed control which is primary requirement of DC traction.