The document discusses terminal voltage in an electrical system. It provides formulas for calculating terminal voltage (V), generated emf (E), armature current (Ia), and other variables. As an example, it calculates: 1) A load current (IL) of 100A for a 20kW load drawing power from a 200V source. 2) A voltage drop of 10V in cables to the load, making the terminal voltage 210V. 3) A field current (If) of 4.2A through a field coil with resistance of 50 ohms. 4) The armature current (Ia) is the sum of the load and field currents, or 104.2

1. Terminal Voltage

4. !

5. Terminal Voltage
V = E - IaRa

6. Generated emf
E = V - IaRa

7. Ia = If + IL
from Kirchhoff ’s current law

8. E = Generated emf
V = Terminal voltage
Ra = Armature resistance
Ia = Armature current
IL = Load current
If = Field Current (I = V)
Rf

10. !
Load current (IL) =
20 kW =
20,000
= 100 A
200 V
200

11. !
Volt drop in the cable to the load
= IL x RC
= 100 (100 x10ˉ³) = 10 V
Hence terminal voltage = 200 + 10 = 210 V

12. !
Field current (If) =
V =
210 =
4.2 A
Rf
50

13. !
Armature current (Ia) = If + IL = 4.2 = 100 = 104.2 A

14. !
Generated emf
(E) = V + IaRa
210 + (104.2 x 40 x10ˉ³)
210 + 4.168 = 214.17 Volts.