Dc Shunt Motor Loadtest 2fc1u

Shiv Nadar University – School of Engineering Electro mechanics Exp no:

Date:

Load Test of DC Shunt Motor Aim: A) To study the characteristics of DC shunt motor. B) To calculate the efficiency of DC shunt motor.

Apparatus: DC shunt motor Name plate details

Sl. No. 1 2 3 4 5 6

Equipment

Rating

Quantity

Voltmeter Ammeter Tachometer Loading Arrangement Rheostat Connecting wires

0-300 V(MC) 0-20 A (MC) 0-1500 rpm Spring pulley type

1 1 1 1

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1 As required

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2014

Shiv Nadar University – School of Engineering Electro mechanics Circuit diagram:

0-20 A A

25 A

IA L F A

MC

220 V DC Supply

Z

RF

V MC VA 0-300 V

A M

25 A

ZZ

AA

Pulley arrangement

Switch-Fuse Unit

Observation table:

Sl. No.

V (V)

I (A)

N (rpm)

W1 (Kgm)

W2 (Kgm)

.

Torque (Tsh)

Input power (Pin)

Output power (PO)

Efficiency (η)

2014

Shiv Nadar University – School of Engineering Electro mechanics Shaft torque Tsh = (W1 – W2) * R Kgm Motor output power PO = (2*π*N*Tsh*g) / 60 watts Where R = radius of drum (m) N = speed of the motor in rpm g = gravitation acceleration (m / sec2) Motor input power Pin = VA*IA watts Efficiency η = (PO / Pin)*100

Procedure: 1) Connect the circuit as per the given circuit diagram. 2) Connect the rheostat in series with the field. 3) At the starting, the weights on the both the springs of the pulley arrangement should be kept at zero position. 4) Initially, the value of rheostat should be at minimum position. 5) Switch on the supply. 6) Gradually in steps, remove the starter resistance. 7) Bring the motor to its rated speed by adjusting the field rheostat. 8) Take the readings at no load. 9) Now, gradually increase the load from the pulley arrangements. 10) Take the readings for different load values. 11) Bring the machine to its no load condition and field rheostat to its minimum position, then switch off the supply.

Plot: 1) 2) 3) 4)

Plot the output power (P0) – efficiency (η) curve. Plot the speed (N) – torque (Tsh) curve. Plot the torque (Tsh) – armature current (Ia) curve. Plot the speed (N) – armature current (Ia) curve.

Precautions: 1) Don’t switch on the supply while making the connections.

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2014

Shiv Nadar University – School of Engineering Electro mechanics 2) Before switching on the supply, make sure starrier is at its maximum position.. 3) All the connections should be perfectly tight. No loose wire should be on the table. 4) Applied voltage should not be more than the rated voltage. 5) Before switching on the supply, ensure there is some water in the drum for cooling purpose.

Result:

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2014