In DC machines (generator or motor), the losses may be classified into 4 categories namely,
- Copper losses
- Iron or core losses
- Mechanical losses
- Stray Losses
1. Copper Loss in DC Machine
In dc machines, the losses that occur due to the resistance of the various windings of the machine are called copper losses. Copper losses are also known as I2R losses because these losses occur due to current flowing through the resistance of the windings.
The major copper losses that occur in dc machines are as,
Where, Ia is the armature current and Ra is the armature winding resistance.
In dc machines, there is also a brush contact loss due to brush contact resistance. In practical calculation, this loss is generally included in armature copper loss.
2. Iron or core losses in DC Machine
The iron losses occur in the core of the armature of a DC machine due to the rotation of the armature in the magnetic field. Because these losses occur in the core of the armature, these are also called core losses.
There are two types of iron or core losses namely hysteresis loss and eddy current loss.
3. Mechanical Loss in DC Machine
Mechanical losses are divided into bearing friction loss and windage loss. The losses occurring in the moving parts of the machine and the air present in the machine is known as Windage losses. These losses are very small.
4. Stray Losses in DC machine
The following factors are considered in stray load losses.
- The distortion of flux because of the armature reaction.
- Short circuit currents in the coil, undergoing commutation.
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