What Are Losses In D.C. Generators And How Many Types Of Losses In D.C.Generator

• What Are Losses In D.C. Generators

Losses In D.C. — A Generators generator transforms mechanical energy into electrical energy. The energy output of a generator should be theoretically equal to the energy input. But, some energy is always lost in the windings, cores, etc. and the output energy is always lesser than the input energy.

⇒The factors which cause loss of energy are as follows:
› Copper losses
› Iron losses
› Mechanical losses
→ Copper losses
The copper losses of electrical losses are caused due to the resistance of brushes, Armature and field windings.
• Armature Loss– The Loss Due to the resistance of the armature coil is equal to I2a . Ra where Ia , is the armature current and Ra is the armature resistance. This loss can reach up to 30 to 50 percent of total electrical energy generated at full load.

• Field Loss– Losses due to the resistance of field and interpoles windings:
In shunt field winding = I2sh . Rsh
In series field winding = I2se . Rse
In interpole winding = I2a . Rip
( Since the interpoles are connected in series with the armature windings, Therefore in the above formula Ia has been used.)
→Iron losses
Iron losses or magnetic losses or core losses are used due to the dissipation of electrical energy by the cores of the field poles, interpoles, and armature drum.
› Hysteresis loss= n . f . B1.6max  joule/meter3
› Eddy current loss- The dissipation of energy due to eddy current can reach up to 20 to 30 percent of the applied mechanical energy.

→Mechanical losses
These losses consist of:
› Friction loss at bearing and commutator.
› Air friction loss of rotating armature.
› Friction loss at brushes.

The total mechanical losses may reach up to 10 to 20% of the applied mechanical energy.

(A) Stray loss- The sum of magnetic and mechanical losses is called stray loss.

(B) constant loss- For shunt and compound generators, field copper loss is constant,
Therefore
Constant loss=Iron loss+mechanical loss+Shunt field loss.

(C) Variable loss-
› For shunt generator= I2a . Ra

› For compound/series generator= I2a . Ra + I2se . Rse

(D) Total loss= Constant losses+Variable losses.