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Home Electrical and Electronics Electrical Machines 1 To conduct load test on dc shunt generator and obtain external characteristics and internal characteristics
Electrical Machines 1 Lab Experiments

To conduct load test on dc shunt generator and obtain external characteristics and internal characteristics



Aim

To conduct load test on dc shunt generator and obtain external characteristics and internal characteristics

Apparatus Required:

S.no Name Range Type Quantity
1 Ammeter (0-20)A MC 2nos
2 Ammeter (0–2.5)A MC 1 no
3 Voltmeter (0-300)V MC 2nos
4 Tachometer (0-10,000)rpm Digital 1no
5 Rheostat 400Ω, 1.7A Wire wound 2nos
6 Connecting wires (0-20)A - Required
7 Load box 230V,5KW/20A Resistive 1 no.

Name plate details:-

Motor Generator

Voltage - 220V Voltage - 220V

Current -19A Current -13.6A

Speed - 1500 rpm Speed - 1500 rpm

Excitation type–shunt Excitation type - shunt

Circuit diagram:

circuit-diagram

To measure armature resistance:

diagram

Procedure:-

  1. Make the connections as per the circuit diagram.
  2. Initially keep the motor field rheostat at minimum resistance position and generator field rheostat at maximum resistance position.
  3. Give the dc supply to the circuit and start the motor with the help starter.
  4. Adjust the generator voltage to the rated value by using generator field rheostat.
  5. Apply resistive load in steps and note down the values of terminal voltage, load current and field current.
  6. Increase the load till rated current is obtained.

To determine Armature resistance:

  1. Connect the circuit as per the circuit diagram.
  2. Switch on dc supply
  3. Increase the load and note down the voltage and current.

Tabular column: Table 1

Terminal Voltage (Volts) Load Current (IL) Field Current (If) I a= IL+ If(amp) E g= V + IaRa(volts)
214.7 0.4 0.5 0.9 215.65
211.8 1.5 0.9 2.4 213.5
208.6 2.5 1 3.5 210.5
206.1 3.5 1.2 4.7 208.38
202 4.5 1.5 6 204.85
198.5 5 1.5 6.5 201.35
194.1 6.5 2 8.5 197.9
191.1 7.5 2 9.5 194.9

Table2: Armature Resistance

V(volts) I(amp) R a= (V/I) (ohms)

Model graph:

model-graph
model-graph-1

Result:Internal and external characteristics of dc shunt generator are drawn by conducting load test on it.

Viva voce

  1. What is the condition for maximum efficiency?
  2. What is the difference between cumulative and differential compound motor?
  3. What is torque?
  4. What is back Emf?
  5. What are the applications of dc shunt motors?











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