A DC machine is an electromechanical device that is used to convert electrical energy into mechanical energy or vice versa.
The DC machine used to convert electrical energy into mechanical energy, which is known as DC motor and the DC machine used to convert mechanical energy into electrical energy, which is known as DC generator. The same machine can be used either as a motor or generator. The construction is same for DC motor and DC generator.
Working of DC Machine
The working principle and operation of a DC machine is based on an effect when a current carrying conductor coils laying in a magnetic field, the magnetic field produces a mechanical force on it known as torque which rotates the conductor coils in magnetic field. The direction of this produced torque can be found by the Fleming’s left hand rule (thumb is the force). The generated force can be calculated as follow.
Construction of DC Machine
The DC machine consists of Yoke, Pole, and Pole shoe, Armature core, Field Winding, Armature Winding, Commutator, Brushes, shaft, and Bearings. Let’s explain each part in detail with applications.
- Yoke or Frame
The yoke is also known as the frame. It covers the internal parts of the machine. The yoke is made up of low reluctance magnetic material like iron and silicon steel. Generally, the yoke is made up of iron because iron is cost-effective material than steel.
The yoke is used to provides mechanical protection to the machine. The second application of yoke is that it provides a low reluctance path to the flux. So, flux completes its path through the yoke.
- Pole and Pole shoe
The field winding is placed on a pole. When current passes through the field winding, it will create an electric magnetic field and behaves as an electromagnet. The pole shoes expand flux in the entire machine.
To reduce the eddy current losses, the pole and pole shoes are laminated. For a small machine, the pole is not necessary to laminate. It is made up of thin cast steel.
The pole is used to provide housing for the field winding and produce magnetic flux inside the machine. The pole shoes are used to provide support to the field winding and not to slip from the pole.