---
title: "Compare DC shunt and series generators"
subject: "Electrical Machine"
chapter: 3
key: "semester_4/electrical_machine:shunt-series-generator-comparison"
source: https://www.bctengineer.com/q/semester_4/electrical_machine/shunt-series-generator-comparison
site: BCT Engineering
---

# Compare DC shunt and series generators

Electrical Machine · Chapter 3: DC Generator

- Asked in: 2073 Magh, 8 marks
- Video: [Types of DC Generators - Separately & Self Excited DC Generator | Shunt, Series & Compound Generator](https://www.youtube.com/watch?v=xi0jaPAl2II) — Electrical Deck
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/electrical_machine/shunt-series-generator-comparison
- Whole chapter: https://www.bctengineer.com/md/semester_4/electrical_machine/chapter-3

## Question

Make a detail comparison of dc shunt generator and dc series generator with their diagrams, equations and characteristics curve.

## Short answer

Shunt generators have field parallel with armature, many turns of thin wire, voltage drops with load; used for battery charging and lighting. Series generators have field in series, voltage rises then falls; used for boosters and arc lighting.

## Answer

A shunt generator has the field winding connected in parallel with the armature, and a series generator has it in series with the armature and the load.

#### Circuit diagrams
```text
 SHUNT                           SERIES
  +--Ia-->--+---> IL              +--Ia-->--[Rse]---> IL
  |   Ra    |                    (G)                  |
 (G)  Ish  Rsh  [LOAD]            |                 [LOAD]
  |   |      |                    +---------------------+
  +---+------+
```

#### Equations
- Shunt: I_a = I_L + I_sh; I_sh = V/R_sh; V = E_g − I_aR_a − brush drop; E_g = V + I_aR_a
- Series: I_a = I_se = I_L; V = E_g − I_a(R_a + R_se) − brush drop

#### Characteristic curves
```text
  Shunt V-IL           Series V-IL
 V|*****               V|     ****
  |     ***             |   **    ***
  |        **           | *
  |          *          |*
  +-----------> IL      +-----------> IL
```
The shunt external characteristic drops slowly, then turns back near the maximum current. The series characteristic starts from the residual voltage, rises with load, then falls after saturation.

#### Comparison
| Basis | Shunt generator | Series generator |
|---|---|---|
| Field winding | many turns, thin wire, high resistance | few turns, thick wire, low resistance |
| Field connection | parallel with armature | series with armature |
| Field current | I_sh = V/R_sh, almost constant | equals load current |
| Armature current | I_L + I_sh | I_L |
| Voltage build-up | needs no-load start | needs a closed load circuit |
| No-load voltage | full rated voltage | only residual emf |
| V as load increases | decreases slightly | increases then decreases |
| Voltage regulation | fairly good | poor |
| Short-circuit | self-protecting (V and field collapse) | large current, dangerous |
| Uses | lighting, battery charging, excitation | boosters, arc lighting |

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. How does the series generator field winding differ from the shunt?
   A. Many turns of thin wire, high resistance
   B. Many turns of thick wire
   C. Few turns of thick wire, low resistance
   D. Few turns of thin wire
   Answer: C. The series field carries full load current, so it needs thick wire; the shunt field is the opposite. (Key point: Field winding)

2. What is the armature current in each machine?
   A. Shunt: I_L; series: I_L + I_sh
   B. Both: I_L + I_sh
   C. Both: I_L
   D. Shunt: I_L + I_sh; series: I_L
   Answer: D. The shunt field takes a branch current from the armature; in the series machine the field is in the line. (Key point: Armature current)

3. How do they behave on short circuit?
   A. Shunt is self-protecting; series gives a large dangerous current
   B. Both give a large current
   C. Series is self-protecting
   D. Neither is affected
   Answer: A. On short circuit the shunt field collapses with V, while the series field stays excited. (Key point: Short circuit)

## Related in Electrical Machine

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