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 without load or light load?
This can be seen from the speed-armature current and the speed-torque characteristics that on low armature current and low torque condition motor shows a tendency to rotate with dangerously high speed. This is the reason why series motor should never be started on light loads or no load conditions.
Why is a DC series motor used to start heavy loads?
The starting torque of the DC series motor is proportional to the square of the armature current. … That is why DC series motor is capable to produce high starting torque, and it is preferred for driving heavy loads.
Which motor has highest no load speed?
Explanation: At no load, armature current tends to zero, flux φ tends to zero, where speed is inversely proportional to the flux, speed will tend to infinity. Thus, no load speed of DC series motor is highest.
When load is removed motor will run at the highest speed?
Answer : When load is removed, series motor will run at the highest speed.
What will happen when DC shunt motor is started with load?
If the same machine is run as a motor it takes a line current of 20A from 220V supply. … Answer : With the increase in load on a d.c. shunt motor, speed of the motor reduces slightly.
What are the characteristics of DC shunt motor?
Characteristics of a DC Shunt Motor:
- Speed-Armature Current Characteristic: …
- Torque-Armature Current Characteristic: …
- Speed-Torque Characteristic: …
- Break in Field Circuit of a DC Motor:
Which braking is not possible in series motor?
In series motor back emf cannot exceed the supply voltage. So regenerative braking is not possible.
What is the function of NVR coil in 4 point starter?
NVR coil stands for the No-Volt Release coil also represent by NVC. It is used in dc motor starter. No volt coil retains the starter knob in the last step, as far as the supply voltage is available. When supply voltage fails, the knob returns to off position.