What will happen if a shunt DC motor is directly connected to the supply line?

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. 2.

What will happen when the DC shunt motor is connected to AC supply?

The Shunt winding has a large number of turns so that it has appreciable inductance. When A.C is applied to a shunt motor, the large inductive reactance of shunt winding will reduce the field current too much. Consequently, Shunt motor will not usually run on A.C Supply.

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Why DC shunt motor should not be started direct on line?

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 would happen to the DC shunt motor if it is started with full load attached?

On adding a load to the shaft, the motor does slow down initially, but this is where the concept of self regulation comes into the picture. At the very onset of load introduction to a shunt wound DC motor, the speed definitely reduces, and along with speed also reduces the back emf, Eb.

What would happen if you try to start a DC motor without applying field supply?

The motor will try to speed up to develop a back-emf and with no field it requires a very large armature current. … Normally the armature fuses just blow as the current drawn can be very high depending upon the applied armature voltage. In this case the motor will accelerate and run away until the fuses blow.

What happens when you run a DC motor on AC?

As the motor is DC so the field and armature winding made for DC supply. The winding which is made for DC always has more resistance than the winding which is made for AC. … When DC motor Runs on AC supply more loss and heat will occur in the motor.

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What will happen if a DC motor is supplied with AC voltage?

If we give dc supply to a ac motor it draws high current since the resistance of the winding is very low. Also no current will be induced in the rotor from stators dc supply.So motor will not start at all. Ultimately it burnt out.

What will happen if a shunt motor running at no load has its shunt field winding opened accidentally?

Ans: if a shunt motor, running at no load has its shunt field opened or burnt out, the back emf will fall to nearly zero . the armature current will continuously increase the speed of the motor until its parts fly apart.

When motor is directly connected to main supply armature draws?

At starting, when the motor is stationary, there is no back EMF in the armature because the speed is zero. Consequently, if the motor is directly switched on to the mains, the armature will draw a heavy current ( I a = V − E b R a = V R a ) because of small armature resistance.

Why DC shunt motor should be started with load?

When the motor is connected across the supply mains without load, it draws small current from the supply mains. … The increase in back emf weakens the armature current and hence the field current. This cause again increases the speed so the back emf.

What would happen if field of DC shunt motor is opened?

Detailed Solution. For a constant back emf, flux is inversely proportional to the speed of the motor. If field winding is disconnected accidentally, the speed would dangerously increase in order to maintain the back emf of the motor.

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What will happen to a DC motor if the suddenly loaded?

When suddenly loaded, the engine speed decreases suddenly until the governor opens the throttle enough, and for long enough, to get the speed back up to normal. If the engine can’t catch back up right away, it can stall instead.

What is the effect in a DC shunt motor if its supply terminals are interchanged?

When both (the direction of the field as well as that of armature current) are reversed the direction of rotation will not change. So in the case of DC shunt motor, if the supply terminals are interchanged, there is no change in the direction of rotation.

What will happen if shunt field resistance is too large?

Answer: n d.c shunt motor if field winding supply is removed the motor back emf will drop to zero, hence the armature will draw more current to make up the emf. this results in blowing up of fuse.