Multi-Amp TR700 User manual

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PIN 820111/820131
SIN 8470 & UP
910624
TRANSFORMER RATIOMETER
TR700/TR800
CAT, NO, 820110/820130
OPERATING AND INSTRUcnON MANUAL

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TABLE OF CONTENTS
PAGE
1. GENERAL INFORMATION 0 0 0 0 0 0 0 0 • 0 0 0 0 0 0 0 •• •• • • • • 0 • 0 • • • • • • • •• 2
1.l GENERAL DESCRlYI10N ....... . .... . .•..•..•..•. , . . . . . . 2
1.2 FEATURES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . 3
1.3 SPECIFICATIONS. . . . . . . . . . . . . . . . . . . . . • . . • . . . . . . . . . . . . .. 3
1.4 ACCESSORIES FURNISHED . .. ...... . ... ... ....... .... . .. 5
1.5 ACCESSORIES AVAILABLE ... . . ...... . . .......... ...... . 6
1.6 CHANGES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6
1.7 WARRANTY . .. .... ........... .. ..•..• 0 •••• • •• • • • • 0 • • • • 7
2. INSTALLATION
......... .. .. . .... .... ....... . ... .. .. . ....... 8
2.1 UNPACKING AND INSPECTION. . . . . . . . . . . . . . . . . . . . . . •. . . . 8
2.2 PREPARATION FOR USE . .
......... .. . .. .. . . .. . .. . . . .... 8
2.3 LINE SUPPLY VOLTAGE ...... . . . ..•.. 00 . ........ .. ..... 8
2.4 REPACKING AND SHIPMENT ....•.. .. ... . .. . .. . ....• . ... 8
3. OPERATING INSTRUCTIONS ......... ... .. . ... . 0 •• 0 • • • • • • • • • •• 9
3.1 PANEL CONTROLS-AND OPERATING FUNCTIONS . . .. . .... . 9
3.2 GENERAL OPERATING INSTRUCTIONS USING A SELF-
CHECK PROCEDURE (Ratio 1:1)
........... ...... . .... . .. 13
3.3 MEASUREMENT OF SINGLE-PHASE, TWO-WINDING
TRANSFORMERS . . . . ... . .. .. .. . .. . .. . . ........ . . .. 0 0 • • 17
3.4 SINGLE PHASE AUTO TRANSFORMERS AND
REGUlATORS ... 0 0 • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 21
3.5 DETERMINING TRANSFORMER CONNECTIONS USING
ONLY NAMEPLATE DATA
........... . ......... _. . .. . . .. 24
3.6 lHREE PHASE TRANSFORMERS (Two Windings) 0 • • • • • • • • • •• 26
3.7 THREE PHASE AUTO TRANSFORMERS . ........ . ..... . 0 •• 26
3.8 INTERPRETATION AND PROPER USE OF TI:IE RATIO
DEVIATION DIAL .... .. . .. .......... . .. ... 0 • •• •• • • • 0 • • 29
3.9 CURRENT TRANSFORMERS ...................... .. .... 31
3.10 INSTRUMENT VOLTAGE TRANSFORMERS . . . . . . . . . . . . . . .. 34
4. TROUBLE SHOOTING ..............................•... _. . . . 37
4.1 SETTING OF DEVIATION DIALS . ..... . . 0 •••••••••• • 0 • • • • 37
4.2 QUICK REFERENCE TROUBLE CHECK . . 0 • • • • •• 0 0 • • • • • • • • 38
5. SERVICE AND MAINTENANCE ............. . .... . ... . ...... . . _ 39
5.1 DOCUMENTATION . . . . . .... . . . .. .... . .. 0 • • •• 0 •• • 0 0 • 0 • • 39
PIN 820 111 /820 131
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I. GENERAL INFORMATION
1.1 GENERAL DESCRIPTION
The
1R800 is a portable instrument designed for the accurate ratio
measurement of transformers and all devices with AC ratiometric divider s
associated with them.
Built into the TR800 is a current meter for the measurement of the ex citing
current of the transformer under test. Keeping a hi s tory ofexcitation current
has proved to be a reliable way of detecting problems in transformer s.
The phase deviation feature of the 1R800 gives the operator the phase
difference between
primary and secondary voltages, which is useful in
determining if there are shorted turns or whether the winding has an unequal
number
of turns connected in parallel.
Three-phase switching on the
1R800 simplifies test procedures, saves time
and greatly reduces the risk of electric shock.
1.2 FEATURES
-Built-in three-phase lead switching.
-High ratio range; 1:1 to
2021 :1.
-Ratio's all types of C.T.s.
-Full internal protection from over-voltage and shorted output conditions.
-True four terminal measurements for high ·accuracy.
-Direct reading of percent deviation of transformer ratio .
-Phase angle measurement
provided to give more accurate indication of
transformer condition.
-Durable transport case provided for longer instrument life.
-Built-in current meter for performing excitation tests.
P /N 820 111 /820 131 3

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1.3 SPECIFICATIONS
P IN 8201 11 /820131
Specifications:
Bridge:
25 ' C ±5' C 6 months 50 or 60Hz
±2Hz.
Transformer ratio
arm bridge circuit with phase
sensitive null detector.
Bridge Output Test Voltage : 120V, 1A isolated, line dependent.
12V,
1A isolated, line dependent.
Frequency: 50
or 60Hz depending on line
frequency.
Ratio Measurements:
(Exclusive of % Deviation Dial)
Multiplier
0.1
0.2
05
1.0
2.0
5.0
10.0
20.0
50.0
100.0
Accuracy:
NOTE:
% Deviation Dial
Resolution
0.001
O'(lO2
0.005
0.01
0.02
0.
05
0.1
0.2
05
1.0
±0.1%
of ratio.
Maximum Range
2.000:1
4.000:1
10.00:1
20.00:1
40.00:1
100.0:1
200.0:1
400.0:1
1000.0:1
2021.0:1
Display by 1R800 is ratio at test voltage (12 or 120V)
and may not be ratio of device at its rated voltage or
current.
Maximum Range: +0.5 to -0.5 percent of ratio reading.
0. 02% of ratio reading.Resolution:
Accuracy:
±2% of dial reading.
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1.3 SPECIFICATIONS (continued)
1.3 SPECIFICATIONS (continued)
PIN 8201 11 {820131
Phase Deviation Dial
Multiplier
0.1
1.0
Accuracy:
NOTE:
Excitation Meter
Multiplier
1.0
10.0
Accuracy :
Protection
Resolution
O.02CR
0.2 CR
±2% reading.
Maximum Range
±05CR
±S.OCR
1 centiradian (CR) = 34.S minutes.
60 minutes = 1 degree.
Resolution
2rnA
20rnA
±3% fuU scale.
Maximum Range
SOmA
SOOrnA
. " XC' Input: IS0V RMS maximum beforeprotection shorts XO to Xl.
Energizing X side of transformer instead of H side) will
usually try to develop in excess of lS0V on X side of
TR800 thereby enabling protection to short XO to Xl.
This prevents any damaging voltage from entering the
instrument .
Resettable Circuit Breaker:
2A maximum fast acting; 0.1 second tum-off time. Prevents
any circuit damage due to high currents created when the
output supply is shorted or test transformer is connected
backwards.
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1.4
1.5
Physical:
Instrument and accessories supplies with portable foam-lined
canying casC. Case has hinged opening from above with a
lockable latch.
Sizes: Instrument :
Case: 400 x
220 x 250mm (IS x 9 x 10 inches)
480 x 530 x 370mm (19 x 21 x 14 inches)
Weight: Instrument: 9kg (20 lbs)
12kg (27 lbs)Shipping:
ACCESSORIES FURNISHED
The TR700 Transfonner Ratiometer
is supplied complete with:
820111 Instruction Manual
820112 Set of 10m leads
Transport Case
AC Line Cord
The TR800 Transformer Ratiometer
is supplied complete with:
820131 Instruction Manual
820132 Set of 10m Leads
.Transport·Case
AC Line Cord
ACCESSORIES AVAIlABLE
820111
820112
820113
820116
820118
820131
820132
820133
820134
820135
820136
Operating and Instruction Manual, TR700
10M Test Leads
25M Test Leads
Range Extension Transformer, 5:1/2: 1, Step-up
CCYT Ratio Test Extension Adaptor
Operating and Instruction manual, TR800
10M Test Leads
25M Test Leads
Invertor, 12VDC to 120VAC
10M Test Lead Extension
25M Test Lead Extension
1.6 CHANGES
P{ N 820 111 /820131
Please Dote that this instrument is subject to continuous development,and
improvement. This instrument may therefore incorporate minor changes in
detail from the information contained herein.
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1.7
PIN 820 111 /82 0131
WARRANTY
Multi-Amp warrants this instrument sold by us or our authorized agent s, to
be free from defects in material and workmanship for a period of 12 months
from date of shipment. During the warranty period, Multi-Amp will,
at our
option, repair or replace the Instrument or part thereof which proves to be
defective providing:
(1) The Instrumentisreturned properlypackedand transportationprepaid
with prior authorization from us or our appointed agent,
(2)
The Instrument has not been altered, modified or repaired by
unauthorized personnel and,
(3) That our examination discloses to our satisfaction that any improper
operation
or failure was the result of defective material or
workmanship and was not the result of improper use, negligence or
accident, exceeding environmental limits, or connecting the instrument
to incompatible equipment.
This warranty
is exclusive and is given and accepted in lieu of all other
warranties, express or implied, and constitutes flllfil1ment of all our liabilities
to the purchaser. Multi-Amp specifically disclaims the implied warranties of
merchantability and fitness for a specific purpose. We assume no liability, in
any event, for consequential damages, for anticipated or lost profits, for
personal injury due to use or accident, for incidental damages or loss of time
or otber losses incurred by the purchaser or any third party in connection with
instruinents covered by this warranty
or otherwise.
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2.
INSTALlATION
2.1
2.2
2.3
UNPACKING AND INSPECTION
Prior to shipment this instrument was electrically tested and mechanically
inspected and found to meet specifications and be free ofmechanical defects.
After unpacking the instrument, visually inspect the instrument and
accessories
for damage . H evidence of damage is present YOU must contact
the carrier who transported the unit and file a claim in writing. The shipp ing
container and packing material should be retained for inspection by the
carrier's agent. Electrical operation per section 3 should be checked
as soon
as possible after shipment.
PREPARATION FOR USE
INSURE
THAT1HE APPARATUS TO BE TESTED IS CLEARED AND
DE-ENERGIZEDPRIOR
TO TEST. It is highly recommended that the user
familiarize himselfwith the controls, functions and features detailed
in se.ction
3 prior to use.
UNE SUPPLY VOLTAGE
This instrument is shipped from the factory for operation on either 120V,
60Hz line or 220V, 50Hz. Voltage is noted on the test report. To prevent
damage to the instrument, ensure that the voltage
on the test 'report matches
your particular line voltage.
2.4 REPACKING AND SHIPMENT
To insure proper shipment of thi s instrument it is recommended that the
original reusable container and packing material be retained. If being
returned for calibration or service, please attach a card to the instrument
specifying the owner, model and serial number and service required.
P IN 820111/820131 8

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3. OPERATING INSlRUCTIONS
3.1 PANEL CONlROLS AND OPERATING FUNCTIONS
PIN 8201ll/82OlJl
This section details and describes the operating features of the lR700 and
lR800. (Refer to Figures 1 and 2). .
1. Line Input Socket -Standard input for line cord provided.
2. Instrument ON -Flipping this switch upwards activates the instrument,
immediately sending voltage to the
"H" output terminals. This switch
is also a fast-acting circuit breaker, therefore, protecting the instrument
by shutting itself off. To reset, simply flip switch upwards.
3. Power
ON Indicator -This red LE.D. is illuminated when instrument
is energized.
4.
5.
6.
7.
8.
9.
Detector Phasing Switch -State of bridge balance of ratio or phase
deviation. Null meter (17)
is indicator for balance condition.
Detector Sensitivity - The sensitivity of null meter (17) is controlled
with this adjustment. As a general rule, the higher ratio's require
higher sensitivity.
ego A 1:1 ratio, therefore would require the lowest
gain and a
2000:1 ratio would require a high sensitivity setting.
Phase Multiplier Switch -The approximate range of phase deviation
is determined with this switch.
Phase Deviation Dial -The precise value of phase deviation
is
determined by this setting in conjunction with the phase mu ltiplier
switch (6).
Ratio Multiplier Switch -The approximate range of the ratio being
tested
is determined with this switch.
Ratio Switches -These switches determine the "Ratio" of the test
transformer, when used in conjunction with ratio multiplier (8).
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3.1 PANEL CONTROLS AND OPERATING FUNCTIONS (continued)
3.1 PANEL CONTROLS AND OPERATING FUNCTIONS (continued)
P IN 820111/820131
10. Ratio Deviation Dial- Once thecalculated transformer ratio is entered
into the ratio switches (9) and ratio multiplier (8), this dial gives a
direct reading
of percent deviation of the test transformer versus the
entered ratio. When balancing ratio switches, this dial should
ALWAYS be in "0" position.
11. "X" Input-This connector couples with the provided leads marked "XO
to X3".
12 . "H" Input-This connector couples with the provided leads marked "HO
to ID
It
,
13.
14 .
15.
16.
17.
18.
19.
20.
21.
"X" Selector -This switch selects input to be measured from "X Lead"
connections.
"H" Selector -This switch selects input to be measured from "H Lead"
connections. .
Polarity -This switch reverses iile polarity of measured ratio and also
acts as a polarity indicator.
Test Voltage Selector -This switch applies 12V
or 120V to the test
transformer. 12V is generally used for C.T.s where cores saturate at
low voltages.
Null Meter -Indicator for balance of ratio and phase. Detector
phasing switch (4) determines which
is being balanced.
Excitation Ammeter - This meter indicates the amount of current
required to excite the test transformer at the selected test voltage (16)
under no load conditions.
Excitation Range Switch - The appropriate range of excitation current
(18) is determined with this switch.
"x" Input -These binding posts couple with the provided leads. .
"H" Input -These binding posts couple with the provided lead s.
10

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3.! PANEL CONTROLS AND OPERATING FUNCTIONS (continued)
~ / N U) 1ll / C20131
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PANEL CONTROLS AND OPERATING FUNCTIONS -TR800
FIGURE!
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3.1 PANEL CONTROLS AND OPERATING FUNCTIONS (continued)
Hx
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PANEL CONTROLS AND OPERATING FUNCTIONS· TR700
FIGURE 2
12

3.2
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PIN 820 lll /8 20 m
GENERAL· OPERATING INSlRUCTIONS USING A SELF·CHECK
PROCE DURE (Ratio 1:1)
lR800 (Refer to Figure I)
1. Insure that instrument power switch (2) is in down position.
2.
3.
4.
5.
Connect high side leads(H markings on alligator clips) to "H"
input(12). Connect low side leads (X markings on alligator clips) to
"X" input(ll) .
Short all alligator ends as follows:
HO to XO HI to XI
H2 to X2 H3 to X3
If line cord is not plugged into instrument, do so now.
Set the lR800 instrument controls as follows
Detector phasing switch: Ratio.
Detector sensitivity: Midway.
Phase multiplier switch:
0.1.
Phase deviation dial :· O.
Ratio multiplier switch: 0.1.
Ratio switches: 10 .. 0 . O.
Percent deviation dial: O.
"X" Selector switch : X3 - X2 .
"H" Selector switch: H3 - H2 .
Polarity switch: Normal.
Test voltage selector: 12V.
Excitation range switch: x
10.
6. Ensure that personnel are kept clear ofalligator clips. Clips should.be
clear of ground or any metal objects, as they will be at a potentia
lly
lethal voltage.
7. Tum power switch ON.
8. Observe "Null Detector" needle. It should be pointing towards "0". If
not, obtain centre balance by adjusting "Percent Deviation Dial". Dial
should remain at approximately "0" (±I division) with needle balanced
at centre "0" position.
9. The excitation meter should read approximately " 0" . If not, just above
the "0" line.
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3.2 GENERAL OPERATING INSTRUcnONS USING A SELF-CHECK
PROCEDURE (continued)
PIN 820 111 /820131
10. Set 'Test Voltage Selector" to "120V". Re-adjust "Percent Deviation
Dial". Itshould still balance at approximately
"0". If needle movement
is too sensitive, set "Detector Sensitivity" back until needle movement
is comfortable to operator (this does not affect accuracy).
If all of the above goes accordingly, the instrument has been balanced to a
ratio of
1.000 :1.
11. Switch detector phasing switch to "Phase".
12. Observe "Null Detector" needle. It should point towards centre "0" , if
not, obtain centre balance by adjusting phase deviation dial (7). Dial
should remain at approximately
"0" (±I division) with needle balanced
at centre "0" position.
If all ofsteps 11 and 12 go accordingly, the instrument has been balanced to
a phase deviation of O.O.CR (centiradians) which indicates the internal
reference transformer
is okay. The following steps will verify the correct
operation of the
"X" and "H" selector switches (13 & 14) and the
corresponding H and X leads.
13. Turn instrument OFF.
14. Set "R" selector to " HZ -HI". Set "X " selector to "X2 -XI".
15. Turn instrument ON.
16. "Null Detector" needle should be balancedwith detector phasingswitch
on "Ratio" and "Phase.
17. Repeat steps 13 to 15. Exchanging the following:
"- HZ - HI to HI - ID.
X2 - XI to XI - X3, then,
b.
HI - ID to HI - HO.
XI - X3 to XI - XO, then,
c.
HI - HO to HZ - HO .
XI - XO to X2 - XO, then,
d. HZ-HOtoID - HO.
X2-XOtoX3-XO .
This should fully complete a self-test of the instrument as well as the test
leads.
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3.2 GENERAL OPERATING INSTRUCTIONS USING A SELF-CHECK
PROCEDURE (continued)
3.2
PIN 820 111 /82013 1
GENERAL OPERATING INSTRUCTIONS USING A SELF-CHECK
PROCEDURE (continued)
TR700 (Refer to Figure 2)
1. Insure that instrument power switch (2) is in down position.
2. Connect high side leads ("H" markings on alligator clips) to "H" input
(2
1) (HlC , HIP, H2C and H2P).
3. Connect low side leads ("X" markings on alligator clips) to "X" input
(20) (Xl and X2).
4. Short all clip ends as follows:
HI to Xl
H2 to X2
5. If line cord is not plugged into instrument , do so now .
6.
7.
Set the TR700 instrument controls as follows
Detector phasing switch: Ratio.
Detector sensitivity: Midwa
y.
Phase multiplier switch: 0. 1.
Phase deviation dial: O.
Ratio multiplier switch: 0. 1.
Ratio switches: 10. - 0 - O.
Percent deviation dial: O.
Test voltage selector: l2V .
Ensure that personnel are kept clear ofalligator clips. Clips should be
clear of ground or any metal objects, as they will be
at a potentially
lethal voltage.
B. Turn power switch ON.
9. Observe "Null Detector" needle. It should be pointing towards "0" . If
not, obtain centre balance by adjusting "Percent Deviation Dial". Dial
should remain at approximately "0" (±l divi sion) with needle balanced
at centre " 0" position.
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3.2 GENERAL OPERATING INSTRUcnONS USING A SELF-CHECK
PROCEDURE (continued)
3.2
P IN 820111/820131
GENERAL OPERATING INSTRUcnONS USING A SELF-CHECK
PROCEDURE (continued)
10. Set "Test Voltage Selector" to "120V". Re-adjust "Percent Deviation
Dial".
It should still balance at approximately "0". If needle m~vement
is too sensitive, set "Detector Sensitivity" back until needle movement
is comfortable to operator (this does not affect accuracy).
If all of the above goes accordingl y, the instrument has been balanced to a
ratio of 1.000:
1.
11. Switch detector phasing switch to "Phase".
12 . Observe "Null Detector" needle. It should point towards centre "0" , if
not, obtain centre balance
by adjusting phase deviation dial (7). Dial
should remain
at approximately "0" (±1 division) with needle balanced
at centre
"0" position.
If all of steps 11 and 12 go accordingly, the instrument has been balanced to
a phase deviation of 0.0
CR (centiradians) which indicates the internal
reference transformer is okay.
This should fully complete a self-test of the instrument as well as the test
leads.
16

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PIN 820111/820131
MEASUREMENT OF SINGLE-PHASE, TWO-WINDING
TRANSFORMERS (Refer to Figures 1 and 2)
1. Insure that instrument power switch (2) is in down position.
2. Connect high side leads ("H" marking on alligator clips) to " H" input
(12 & 21).
3. Connect l ow side leads ("X" markings on alligator clips) to "X" input
(11 & 20).
4. Assuming the transformer under test has the following markings:
FIGURE 3
Connect the TRSOO leads to the corresponding markings:
"H" Leads -H1 to Hl. "X" Leads - Xl to Xl.
-H2 to H2. - X2 to X2.
5. Ensure that the remaining leads (H3, HO, X3, XO) are free and
clear of the test transformer and any grounded points, as they
may
accidentally be energized.
6. Set the instrument controls as follows:
Detector phasing switch: Ratio.
Detector sensitivity: Midway.
Phase multiplier switch: 0.1.
Phase deviation dial:. O.
Ratio multiplier switch: 0.1.
Ratio switches: S. - 0 - O.
Percent deviation dial O.
"X" Selector switch: X2 - Xl.
"H" Selector switch: H2 - Hl.
Polarity switch: Normal.
Test voltage selector:
12V.
Excitation range switch: x 10.
17

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3.3
3.3
PIN 820111j820131
MEASUREMENT OF SINGLE-PHASE , TWO-WINDING
TRANSFORMERS (continued)
MEASUREMENT OF SINGLE-PHASE, TWO-WINDING
TRANSFORMERS (continued) .
It should be noted that the test voltage, 12V is used in this application to
achieve an approximate balance, and therefore ratio, unless test specimen is
a current transformer where upon 12V is used to achieve final balance as well
7. Ensure that personnel are kept clear of alligator clips and test
transformer.
8.
9.
10 .
Turn power switch ON.
Observe "Null Detector" needle (17). It will be pointing to the left
side of the meter.
(If not, check polarity switch (normal) and lead
connections
("H" on high side and "X" on low side» .
While still observing "Null Detector", tum ratio multiplier switch
clockwise until null detector (17) swings to the right. Turn ratio
multiplier switch counter-clockwise one position.
ego
Needle swings right on "10" multiplier. Switch should be placed
in "5" multiplier before continuing to next step.
11. With the ratio in approximate range (needle pinned to left), rotate left
most ratio switch (9)
cloc1cwise (start on "8") until null indicator swings
right. Turn ratio switch back one position.
12. Rotate middle ratio switch clockwise (start on "0") until null indicator
swings right. Turn ratio switch back one position.
13. Rotate right most ratio switch clockwise until needle either swings
right or comes to a balance in the centre of the meter.
14. If null detector needle is still settled either left or right of centre,
rotate percent deviation dial (10) until needle balances to zero.
15. Switch detector phasing switch to "Phase".
16. Adjust phase deviation dial (7) until "Null Detector" (17) balances
to
centre "0".
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3.3 MEASUREMENT OF SINGLE-PHASE, TWO-WINDING
TRANSFORMERS (continued)
3.3 MEASUREMENT OF SINGLE, TWO-WINDING TRANSFORMERS
(continued)
PIN 820111/820131
17 . If balance is not possible, switch phase multiplier switch to "I" and re-
attempt step
16.
18.
Once balance is achieved, set ''Test Voltage Selector" to "120V" and re-
balance. (Adjustments should be minimal). 120V should only be used
for C.T.s that have sufficient core to handle this voltage. Otherwise,
12V
is used on ITs.
EXAMPLES OF DIAL INTERPRETATION
After the ratiometer is balanced, the ratio of the transformer under test is
determined as follows:
IT ratio deviation dial is not used, i.e. set · at 0, then;
Ratio = Multiplier x Reading on Ratio Dials
Examples:
1. If multiplier is 0.1 and ratio dials read 17 .32, then:
Ratio = 0.1 x 17.32 = 1.732 or 1.732:1
2.
If multiplier is 0.5 and ratio dials read 10.02, then:
Ratio = 0.5 x 10.02 = 5.01
or 5.01:1
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3.3 MEASUREMENT OF SINGLE-PHASE, TWO-WINDING
TRANSFORMERS (continued)
PIN 820 1I1 f82()13l
If ratio deviation dial (10) is used for balancing, determine ratio as on
previous page and multiply obtained ratio by a factor 1000 + D to obtain
exact value.
1000
Examples:
1. If ratio dial reads 10.00, multiplier is 2.0 and deviation dial reads + 1.5,
then:
Ratio = 2 x
10.00 x 1000 + 1.5
1000
= 20.00 x 1001,5
1000
= 20 . 03
The ratio deviation dial is most useful when percent deviation from a
predetermined value has to be determined. If the deviation dial reads
positive then the ratio of the transformer under test
is higher than the preset
value. Similarly, if the ratio of the transformer under test is lower than the
preset value, then the deviation dial will read a negative value.
Examples:
Name plate ratio 4800 volts
to 120 volts.
Ratio = 40.00
Set multiplier and ratio dials
to obtain a ratio of 40.
Two possibilities exist: M = 2, R = 20.00 (19 + 1 + 0) or,
M =
5,R=8.0(8 + 0 + 0)
Now balance only with ratio deviation dial. Deviation dial reads in mils (1
mil = 1/1000 or 0.1%) as to how high or l ow the ratio is from nameplate.
When obtaining ratio readings, the second and third ratio dials
may exceed
9. If that occurs they should be read in the following manner:
8 + 10 + 9 = 9.09
19 + 11 + 10 = 20.20
10 + 0 + 10 = 10.10
20