Page 332 - CTS - Mechanic Diesel - TP

MECHANIC DIESEL - CITS

6 Adjust the field rheostat of the prime mover to cut out position, and the field rheostat of the exciter in the
minimum voltage position
7 Check the couplings

Table1
Name plate details

Manufacturer,TradeMark:....................................
Type,modelorlistnumber:....................................
TypeofCurrent :.................................... Fabricationorserialnumber :..............................
Function :.................................... Alternator :..............................

Typeofconnection :.................................... P.F. :..............................
Ratedvoltage :....................................Volts Ratedcurrent : amps
Frequency :....................................Hz Ratedspeed : r.p.m.
Ratedpower :....................................kVA Ratedexc.current : amps

Ratedexc.voltage :...................................Volts Directionofrotation :..............................
Ratingclass :................................... Protectionclass :..............................
Insulationclass :...................................

8 Switch `ON’ the prime mover and start the prime mover through the starter switch.
9 Adjust the speed of the prime mover throug hits field rheostat to the rated speed of the alternator.
10 Switch`on’the DC supply to the exciting winding of the alternator. Note down the field current, line voltage and
phase voltage of the alternator in Table 2.
11 Note down the frequency (ifpossible,forthe frequency meter may not read at a low voltage) in Table 2.
12 Increase the field current in10to12equals teps.For each step measure the phase voltage, line voltage frequency
and field current and enter the values in Table 2.

S.No. Fieldcurrent I Linevoltage V Phasevoltage V Frequency V F Remarks
L
P
F

13 Until the alternator output voltage reaches its rated value.

The field current should be varied gradually in equal steps in the ascending order. Otherwise it will
disturb the shape of the plotted curve.

14 Increase the excitation current such that the alternator line voltage is about 10% above the rated value.
15 Draw the curve IF versus VP taking IF on the `X’ axis and VPonthe `Y’axis.The curve shows the O.C.C. or the
magnetization on characteristic of the alternator.
16 Write your conclusion regarding the relation between the field current and phase voltage as well as the line
voltage and phase voltage.

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CITS : Automotive - Mechanic Diesel - Exercise 18.3