What happens if a shunt 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.

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.

What will happen if the motor is directly connected to supply without any starter?

At instant starting of DC motor, back emf is zero. So if we apply rated voltage without starter, then starting current will be dangerously high. This high current will cause mechanical stress and also heats the winding and result in damage to windings.

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.

How is a shunt motor started why it should not be started direct on line?

Direct-on-line (DOL) starting are not used for large DC motor because the starting current will be enormously high which will cause large voltage drop in the supply mains and armature may get damaged due to excessive heating. The armature current of DC shunt motor .

What will happen if back emf vanishes suddenly?

Detailed Solution. 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.

What happens in a shunt dc motor if its field circuit opens while it is running?

If the shunt field suddenly opens while the motor is being operated under full-load conditions, only a small voltage due to the residual magnetism of the pole pieces will be induced into the armature. Current will increase considerably. Under these conditions, the motor will act as a series DC motor.

When a DC machine is connected to the DC supply mains it will produce?

A 4 pole, 500V shunt motor has 720 wave connected conductors on its armature. The full load armature current is 60A and flux per pole is 0.03Wb….

Q.	When a dc machine is connected to the dc supply main it will produce:
C.	emf decreases with time
D.	none of the above

What would happen if a DC motor is directly switched on to the supply without any starter?

What will happen if DC motor is used without starter? Explanation: It would cause intolerably heavy sparking at the brushes which may destroy the commutator and brush-gear. Sudden development of large torque will cause mechanical shock to the shaft, reducing its life.

What is shunt wound motor?

shunt-wound in Electrical Engineering A shunt-wound motor or generator has the field and armature circuits connected in parallel. Current in the field windings of a shunt-wound generator is independent of the load current, because currents in parallel branches are independent of each other.

Why will armature draw heavy current when motor is directly switched on to the main supply Mcq?

When the motor is at rest the speed of DC motor is zero, therefore back emf is zero and if a DC motor is connected directly to the supply mains a heavy current (about 10-12.5 times of rated current) will be drawn because from emf equation of armature circuit , armature current at starting is given as Ia = Vt / Ra and …

What happens when AC is applied to a shunt motor?

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.

What is the difference between DC series motor and DC shunt motor?

The field winding of a dc series motor has fewer turns and larger wire than the field winding of the dc shunt motor. Therefore, its inductive reactance is less. The strength of the magnetic field is about the same as when the motor runs on dc power. The field winding and the armature winding are connected series.

What happens if you connect a DC motor to an AC source?

What will happen if you connect a dc motor to an ac source? When the ac source changes polarity, the current in the motor will reverse. But the reversal will occur in both the armature winding and the field winding. Therefore, the torque on the armature will remain in the same direction.

What is an over excited synchronous motor?

An over excited synchronous motor is called synchronous capacitor, because, like a capacitor, it takes a leading current What could be the reasons if a synchronous motor fails to start? It is usually due to following reasons Voltage may be too low