If it is started without load the field current will be less, hence flux will be less and due to this motor speed will go infinite and damages itself. This is the reason why series motor should not be started without load and shunt motor can be started without load.
Can we start the DC shunt motor and series motor without load?
We can operate a shunt motor with no load because their torque is not that high as series motors. They are moreover constant speed motors and tend to operate at stable speeds. Series motors cannot be started without load, as they tend to overspeed and get damaged. Motor armature current is decided by the load.
Which motor Cannot be started under no load condition?
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.
Why must the series motor be started with load?
At the starting of the motor there is no back emf, so large current current flows cause high starting torque. This starting torque leads to very fast acceleration of motor if shaft is not connected to any load. This fast acceleration cause motor to damage. So series motor are always started with load.
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. … This is the reason why series motor should never be started on light loads or no load conditions.
Why starter is used in DC shunt motor?
Starters are used to protect DC motors from damage that can be caused by very high current and torque during startup. They do this by providing external resistance to the motor, which is connected in series to the motor’s armature winding and restricts the current to an acceptable level.
Why DC shunt motor is not starting with heavy loads?
This is because of stray losses. The heavy starting loads require more armature current, so shunt motor should not be started on heavy loads. … 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.
Which model should not be started on no 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 DC series motor should never be started or Operated on light loads or No load conditions.
What will happen if the starting resistance is not provided?
If there really were no resistance in the circuit, the electrons would go around the circuit, and arrive back at the beginning of the circuit with as much energy as the potential difference (the voltage). That final energy is usually what is dissipated as heat or other types of energy by the circuit.
Which type of load is connected to the DC series motor?
A series DC motor connects the armature and field windings in series with a common D.C. power source. The motor speed varies as a non-linear function of load torque and armature current; current is common to both the stator and rotor yielding current squared (I^2) behavior.
Which motor is always started with load?
At no load, it will rotate at dangerously high speed 2. It will fail to start 3. It will not develop high starting torque 4.
When load is removed motor will run at the highest speed?
1 Answer. When load is removed, series motor will run at the highest speed.
Where is DC shunt motor used?
The applications of shunt DC motor include the following. These motors are used wherever stable speed is required. This kind of DC motor can be used in Centrifugal Pumps, Lifts, Weaving Machine, Lathe Machines, Blowers, Fans, Conveyors, Spinning machines, etc.
Is advised not to run dc series motor with no load why?
It is advised not to run dc series motor with no load. … Explanation: If the torque is zero in dc series motor then the speed will be infinite causing the damage of the machine permanently.
What will happen if DC shunt motor is connected across AC supply?
What will happen if DC shunt motor is connected across AC supply? Explanation: In case of parallel field connection, it won’t rotate at all and will start humming and will create vibrations, as a torque produced by positive and negative cycle will cancel out each other. DC motor will be heated up and it may burn.
When the motor runs on no load then back EMF is?
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.