## What Are Losses In D.C. Generators

**Losses In D.C. —**A Generators generator transforms

*into*

**mechanical 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.*

**electrical 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 I
^{2}_{a }. R_{a}where I_{a}, is the armature current and R_{a}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:

^{2}

_{sh }. R

_{sh}

In series field winding = I

^{2}

_{se}. R

_{se}

In interpole winding = I

^{2}

_{a }. R

_{ip}

( Since the interpoles are connected in series with the armature windings, Therefore in the above formula I

_{a}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 . B

^{1.6}

_{max }joule/meter

^{3}

› 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= I

^{2}

_{a }. R

_{a}

› For compound/series generator= I

^{2}

_{a }. R

_{a}+ I

^{2}

_{se }. R

_{se}

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

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