Page 92 - CITS - Electrician - Trade Practical

ELECTRICIAN - CITS

MODULE 7: Electrical Power, Power Factor &
Electrical Energy

EXERCISE 38 : To measure the 3 Ph. Power by two
wattmeter method

Objectives

At the end of this exercise you shall be able to:
• check the terminals & connection of 3 ph. Wattmeter
• make the connection of 3 phase resistive and inductive load
• measure the power in balanced / unbalanced 3 Ph. Circuits.

Requirements

Tools/Equipments/Instruments
• Combination Plier 165mm, • 3 Ph. Auto transformer
insulated -1 No. 0 - 460 V -1 No.
• Screw Driver 150mm, insulated -1 No. • Multi meter Digital, 3 digit -1 No.
1/2
• Neon Tester 75mm, 500 V -1 No. • 3 Ph. Resistive load 5 KW -1 No.
• Electrician knife insulated -1 No. • 3 Ph. Inductive load 3 KW -1 No.
• Voltmeter MI, 0 - 600 V -2 No’s. Materials/Components
• Ammeter MI, 10 A -2 No’s. • Test lamp 60 W, 230 V -1 No.
• Poly Ph. Watt meter, UPF • TPST switch 415 V, 32 A -1 No.
MI, 600V, 2KW -2 No’s. • Connecting wire 2.5 sq.mm -as reqd.
• Poly Ph. Watt meter, LPF • Cotton waste / cloth - as reqd.
MI, 600V, 2KW -2 No’s.

Procedure

TASK 1 : Identify the 3 ph load and watt meters
1 Draw the circuit diagram of 3 Ph. Power measurement by two watt meter method.
2 Check and identify the type of 3 Ph. Loads - inductive & resistive, type of connection & rating.
3 Check and identify the Watt meters - Type (UPF/LPF), terminals and voltage & current rating.

TASK 2: Connect & measure the power in 3 Ph. Balanced & unbalanced load

1 Make the connections as per the circuit diagram.
2 Check the connections and set the knob of 3 Ph. Auto transformer to zero position.
3 Connect 3 Ph. Input supply and switch ON the TPST switch.
4 Make sure that load switch is OFF, and slowly rotate the knob to set the line voltage (415 V) in 3 ph. Auto
transformer.
5 Record the line voltage (415 V) readings in voltmeter.
6 Close load switch and apply approximately balanced resistive load.
7 Take the readings of wattmeter 1 & 2 and ammeters and record in the tabular column. (Note: For balanced
load ammeters and both watt meters shows equal readings)
8 Switch OFF the mains, and connect the unbalanced load of both resistive & inductive.
9 Switch ON the supply and take the readings of wattmeter 1 & 2 and ammeters and record in the tabular
column. (Note: For unbalanced load ammeters and both watt meters shows unequal readings).
10 Switch OFF the main supply, disconnect the circuit.
11 Calculate the total power (P) consumed in both 3 ph. Loads, as per recorded readings.

75