www.Vidyarthiplus.com
Page |1
SPEED CONTROL OF DC SHUNT MOTOR
AIM:
To obtain speed control of DC shunt motor by
a. Varying
constant.
armature
b.
field
Varying
voltage
current
with
with
field
current
armature
voltage
constant
c.
APPARATUS REQUIRED:
S.No.
Apparatus
Range
Type
Quantity
1
Ammeter
(0-2) A
MC
1
2
Voltmeter
(0-300) V
MC
1
3
Rheostats
-
2
(0-3000) rpm
Digital
1
2.5sq.mm.
Copper
Few
370, 1.1A
100, 1.2A
4
Tachometer
5
Connecting Wires
PROCEDURE:
1.
2.
Connections are made as per the circuit diagram.
After checking the maximum position of armature
rheostat and minimum position of field rheostat, DPST
switch is closed
(i) Armature Control:
1.
Field current is fixed to various values and for each
fixed value, by varying the armature rheostat, speed is
noted for various voltages across the armature.
(ii) Field Control:
1. Armature voltage is fixed to various values and for each fixed
value,
by
adjusting
the field rheostat, speed is noted for various field currents.
www.Vidyarthiplus.com
www.Vidyarthiplus.com
Page |2
2. Bringing field rheostat to minimum position and armature
rheostat
to
maximum
position DPST switch is opened.
MODEL GRAPHS:
OBSERVATION TABLE:
Sl.
No.
Field Control Method
Field
Speed
Armature Control
Armature
Speed
www.Vidyarthiplus.com
www.Vidyarthiplus.com
Page |3
Current
(amp)
(rpm)
Current
(amp)
(rpm)
PRECAUTIONS:
1. Field Rheostat should be kept in the minimum
resistance position at the time of starting and stopping the
motor.
2.
Armature Rheostat should be kept in the maximum
resistance position at the time of starting and stopping the
motor.
RESULT:
Thus the speed control of DC Shunt Motor is obtained using
Armature and Field control methods.
www.Vidyarthiplus.com
www.Vidyarthiplus.com
Page |4
OPEN CIRCUIT & SHORT CIRCUIT TEST ON ASINGLE PHASE TRANSFORMER
AIM:
To predetermine the efficiency and regulation of a
transformer by conducting open circuit test and short circuit test
and to draw equivalent circuit.
APPARATUS REQUIRED:
S.No.
1
Apparatus
Type
Quantity
(0-2)A
MI
1
(0-5) A
MI
1
(0-150)V
MI
2
(150V, 5A)
LPF
1
(150V, 5A)
UPF
1
2.5sq.mm
Copper
Few
Ammeter
2
Voltmeter
3
Wattmeter
4
Range
Connecting Wires
PROCEDURE:
OPEN CIRCUIT TEST:
1.
Connections are made as per the circuit diagram.
2. After checking the minimum position of Autotransformer,
DPST switch is closed.
3. Auto transformer variance is adjusted get the rated primary
voltage.
4. Voltmeter, Ammeter and Wattmeter readings on primary
side are noted.
5. Auto transformer is again brought to minimum position and
DPST switch is opened.
SHORT CIRCUIT TEST:
1. Connections are made as per the circuit diagram.
www.Vidyarthiplus.com
www.Vidyarthiplus.com
Page |5
2.
After checking the minimum position of Autotransformer,
DPST switch is closed.
3.
Auto transformer variac is adjusted get the rated primary
current.
4. Voltmeter, Ammeter and Wattmeter readings on primary
side are noted.
5.
Auto transformer is again brought to minimum position and
DPST switch is opened.
TABULAR COLUMN:
OPEN CIRCUIT TEST:
Vo
Io
Wo
(Volts) (Amps) (Watts)
SHORT CIRCUIT TEST:
Vsc
Isc
Wsc
(Volts) (Amps) (Watts)
www.Vidyarthiplus.com
www.Vidyarthiplus.com
Page |6
FORMULAE:
Percentage Efficiency:
for all loads and p.f.
Output Power
(X) x KVA rating x 1000 x
cos 
Efficiency % = -------------------- = ----------------------------------------------Input Power
Output power + losses
(X) x KVA rating x 1000 x cos 
= -----------------------------------------------------------(X) x KVA rating x 1000 x cos  + Wo +
X2Wsc
Percentage Regulation:
(X) x Isc (Ro2 cos   Xo2sin ) x 100
R% =
-------------------------------------V2
Where X is the load and it is 1 for full load, ½ for half load, ¾
load, ¼ load etc. And the power factor is, upf, o.8 p.f lag and 0.8
p.f lead
PRECAUTIONS:
1. Auto Transformer should be in minimum voltage position at
the time of closing & opening DPST Switch.
www.Vidyarthiplus.com
www.Vidyarthiplus.com
Page |7
SWINBURNE’S TEST
AIM:
To conduct Swinburne’s test on DC machine to
determine efficiency when working as generator and
motor without actually loading the machine.
APPARATUS REQUIRED:
S.No.
Apparatus
Range
Type
Quantity
MC
1
MC
2
(0-1),(0-5),(0-20)
1
Ammeter
A
2
Voltmeter
(0-30),(0-50) V
3
Rheostats
370, 1.7A
Wire
1
Wound
4
Tachometer
5
Connecting Wires
(0-3000) rpm
Digital
1
2.5sq.mm.
Copper
Few
PRECAUTIONS:
The field rheostat should be in the minimum
position at the time of starting and stopping the motor
PROCEDURE:
1. Connections are made as per the circuit diagram.
2. After checking the minimum position of field rheostat,
DPST switch is closed and starting resistance is
gradually removed.
www.Vidyarthiplus.com
www.Vidyarthiplus.com
Page |8
3. By adjusting the field rheostat, the machine is brought
to its rated speed.
4. The
armature
current,
field
current
and
voltage
readings are noted.
5. The field rheostat is then brought to minimum position
DPST switch is opened.
www.Vidyarthiplus.com
www.Vidyarthiplus.com
Page |9
TABULAR COLUMNS:
AS MOTOR:
Tot
S. No.
V
IL
Ia
Ia2Ra
(Volts)
(Amps)
(Amps)
(Watts)
Los
W
(Wa
AS GENERATOR:
2
S.
V
I1
Ia
Ia Ra
No.
(Volts)
(Amps)
(Amps)
(Watts)
TABULAR COLUMN:
S.No.
If (Amps)
Io (Amps)
V (Volts)
DETERMINATION OF ARMATURE RESISTANCE:
www.Vidyarthiplus.com
To
Los
(W
www.Vidyarthiplus.com
P a g e | 10
PROCEDURE:
1. Connections are made as per the circuit diagram.
2. Supply is given by closing the DPST switch.
3. Readings of Ammeter and Voltmeter are noted.
4. Armature resistance in Ohms is calculated as Ra = (Vx1.5)
/I
TABULAR COLUMN:
Voltage
Current
Armature Resistance
V (Volts)
I (Amps)
Ra (Ohms)
FORMULAE:
Hot Resistance Ra = 1.2 X R Ω
Constant losses
= VIo – Iao2 Ra watts
= (Io – If) Amps
Where Iao
AS MOTOR:
Load Current IL = _____Amps (Assume 15%, 25%, 50%,
75% of rated current)
Armature current Ia = IL – If Amps
= Ia2 Ra watts
Copper loss
Total losses
= Copper loss + Constant losses
Input Power
= VIL watts
= Input Power – Total losses
Output Power
Output power
Efficiency %
=
---------------------- X 100%
www.Vidyarthiplus.com
www.Vidyarthiplus.com
P a g e | 11
Input Power
AS GENERATOR:
Load Current IL
= _____ Amps (Assume 15%,
25%, 50%, 75% of rated current)
Armature current Ia = IL + If Amps
= Ia2 Ra watts
Copper loss
Total losses
= Copper loss + Constant losses
Output Power
= VIL watts
Input Power = Input Power +Total losses
Output power
Efficiency %
= ----------------------- X 100%
Input Power
RESULT:
Thus the efficiency of the D.C machine is
predetermined by Swinburne’s test.
www.Vidyarthiplus.com
www.Vidyarthiplus.com
P a g e | 12
REGULATION OF 3–PHASE ALTERNATOR BY EMF AND MMF
METHODS
AIM:
To predetermine the regulation of 3-phase alternator by EMF
and MMF methods and also draw the vector diagrams.
APPARATURS REQUIRED:
SL.NO
1
2
3
4
5
Name of the Apparatus
Ammeter
Ammeter
Voltmeter
Voltmeter
Rheostat
Type
Range Quantity
MC
0 – 1/2 A
1
MI
0 – 5/10 A
1
MC
0 – 10 V
1
MI
0 – 600 V
1
Wire
250 Ω, 1.5
1
wound A
6
Rheostat
Wire
1200Ω,
1
wound 0.8 A
7
Tachometer
Digital
--1
8
TPST knife switch
--1
TABULAR COLUMNS
EMF METHOD:
Eph (V)
SL.NO.
Power
factor
Lag
% Regulation
Lead
Lag
Lead
MMF METHOD:
Ifr
SL.NO.
P.F
Vph
If1
If2
(V)
(A)
(A)
Lag
www.Vidyarthiplus.com
(A)
Lead
Eph
Lag
www.Vidyarthiplus.com
P a g e | 13
PROCEDURE: (FOR BOTH EMF AND MMF METHODS)
1. Note down the name plate details of the motor and alternator.
2. Connections are made as per the circuit diagram.
3. Switch ON the supply by closing the DPST switch.
4. Using the Three point starter, start the motor to run at the synchronous
speed by adjusting the motor field rheostat.
5. Conduct Open Circuit test by varying the potential divider for various
values of field current and tabulate the corresponding Open Circuit
Voltage readings.
6. Conduct Short Circuit test by closing the TPST switch and adjust the
potential divider to set the rated armature current and tabulate the
corresponding field current.
7. The Stator resistance per phase is determined by connecting any one
phase stator winding of the alternator as per the circuit diagram using
MC voltmeter and ammeter of suitable ranges.
2. Draw the Short Circuit Characteristics curve (Short circuit current VS
Field current)
3. Draw the line OL to represent
FORMULAE:
1. Armature Resistance Ra =
Ω
2.
Synchronous Impedance Zs = O.C. voltage
S.C. current
3. Synchronous Reactance Xs = √ Zs2 – Ra2
4. Open circuit voltage for lagging p.f = √(VcosΦ + IaRa)2 +
(VsinΦ + IaXs)2
5. Open circuit voltage for leading p.f. = √(VcosΦ + IaRa)2 + (VsinΦ –
IaXs)2
6. Open circuit voltage for unity p.f =
√(V + IaRa)2 + ( IaXs)2
www.Vidyarthiplus.com
www.Vidyarthiplus.com
P a g e | 14
7. Percentage regulation = Eo – V x 100v
PRECAUTIONS:
(i)
The motor field rheostat should be kept in the minimum
resistance position.
(ii)
The alternator field potential divider should be kept in the
minimum voltage position.
(iii) Initially all switches are in open position.
RESULT:
Thus the regulation of 3-phase alternator has been
predetermined by the EMF and MMF methods.
www.Vidyarthiplus.com