Define DC machine and their types
Define DC machine and their types
The machine which are working on DC supply are known as DC machine. The input of DC machine is always DC but it's not necessary that it always convert into machincal energy. It is also converted into electrical energy. Basically, there are two types of DC machine are:-
1. DC motor:-
The word 'motor' is define as "It is a device which is used to convert electrical energy into mechanical energy". Now, the motor which work on DC supply are called DC motor. Every motor has a shaft which rotates in the presence of magnetic field continuously when current is passed through it. The rotation of shaft are used to drive many device like electric fan, washing machine, etc.
Principle of motor:-
A motor is work on the principle of "when a rectangular coil or loop is placed in a magnetic field and current is pass through the rectangular coil then it produce force which rotates the coil of motor". When rectangular coil rotates then shaft of motor also rotates. In this way electrical energy converted into electrical energy.
Construction of DC motor:-
A DC motor is consist of rectangular coil of copper wire which are placed between two horseshoe type permanent magnet of N and S pole of magnet. In between of horseshoe type permanent magnet a rectangular coil move freely. The side AB and CD are perpendicular to the direction of magnetic field between the poles of magnet. when the side of perpendicular to the magnetic field so that its get maximum magnetic force is extracted on current carrying conductor side of the coil.
A commutator is a rotating device which is used to reverse the direction of current through a circuit. A commutator is a copper ring which are split in two part these two are insulated by each other. The ends of coil are welded with commutator. This commutator help us to proper supply of current in the coil, which generate force and coil is moved continuously. The function of commutator rings reverse the direction of current flowing through the coil after every half rotation of coil.
Why we use of commutator in motor?
We cannot directly connected battery wire to rectangular coil beacuse if we do this, then the connecting wire will get twisted when the coil moves. So, to pass current in the coil we use two strips called brushes. The carbon brush are fixed to base of the motor and they touch lightly the two half ring of the commutator. The working of a carbon brush is that its make contact between commutator and current flowing through it.
Working of DC motor:-
When an electric current pass through a coil in the presence of magnetic field of horseshoe type permanent magnet then the rectangular coil then it produce force which rotates the coil of motor. Let us study in details that how it's happen:-
We know that a electric motor consist of rectangular coil ABCD in between horseshoe type permanent magnet. Now, on the switch, current will through the wire then going to carbon brush. And, carbon brush pass current in the commutator. The current flows in the direction ABCD and leave to another brush.
1. The AB side of rectangular coil ABCD, the direction of current is from A to B. And, in the side CD, the direction of current is from C to D, which is opposite to the direction of AB. According to to Fleming's left hand rule, the force on side AB of the is in downward side whereas the force on side CD of the coil are in the upward direction. Due to this the side AB push down and CD side push upward side. The coil ABCD rotate in anticlockwise direction.
2. When the coil reach vertical position, both the brush are in gap between two commutator ring. So, there is no current flow in the coil. As the results, the coil will not move but this not happen, beacuse it has already gain momentum due to which it goes to beyond the vertical position.
3. After half rotation, the side CD comes is on left side whereas side AB comes on right side, and two commutator automatically change interchange it's position and brush also. According to Fleming's left hand rule, the force on side CD of the is in downward side whereas the force on side AB of the coil are in the upward direction. Due to this the side CD of the coil is pushed down and the side AB of coil is pushed up. This makes the coil rotate anticlockwise by another half rotation.
4. The current in the coil is repeated after every half rotation due to which the coil continue to rotate as longer as current from the battery is passed through it.
2. DC generator:-
The word DC generator means direct current generator. It is a device which is used to convert mechanical energy into electrical energy. The word 'generator' means that 'to generate' or 'produce'.
Principal of DC generator:-
The DC generator is work on a principal of " when the straight wire is moves in the magnetic field then current will be induced in the coil". It is a application of electromagnetic induction.
Construction of DC generator:-
A DC generator is consist of rectangular coil of copper wire which are placed between two horseshoe type permanent magnet of N and S pole of magnet. In between of horseshoe type permanent magnet a rectangular coil move freely. The side AB and CD are perpendicular to the direction of magnetic field between the poles of magnet. when the side of perpendicular to the magnetic field so that its get maximum magnetic force is extracted on current carrying conductor side of the coil. And, maximum current generator to the coil.
Working of DC generator:-
1. When the coil rotate anticlockwise direction, the side AB moves downward side and cut magnetic field lines near the north Pole, and side CD moves up and cut the magnetic field lines near to South Pole magnet. Due to this the current induced in the coil ( According to Fleming's right hand rule).
2. After half rotation, the side AB and CD change its position with each other. Now, the side CD moves downward side and AB moves upward side. As, a result of this, the direction of the current is same as the previous once.