TO 172838
5.1 .4 Potential T ransformer's Ratio
-
Some systems may
include optional, user-provided potential transformers. Their
ratios must be taken into account by means of settings on
Switch
SW2, Nos. 1, 2, 3 and
4,
as listed in Table 5.8.
When external potential transformers are used, calculate
the secondary output level of the transformers by dividing
the nominal voltage input to the PT's primary side by the
turns ratio. The result must be 120 VAC, measured
line-to-line.
Examples:
1. 4160 Volt System: Select a potential transformer with a
4160/120 ratio
=
35/1. Therefore, set switch SW2 for
35:1 ratio.
2. 3300 Volt System: Select a potential transformer with a
3600/120 ratio
=
30/1. Therefore, set switch SW2 for
30:1 ratio.
If potential transformers are not used, select a ratio of 1:1.
5.1.5 3 Wire/4 Wire Line-
The IQ Data can be used to mon
itor either a 3-conductor or 4-conductor AC line. An example
of a 4-wire system is a case in which a transformer's secon
dary is wired in a wye configuration with the G neutral termi
nal ground brought out as the fourth wire. In this case the
G fourth wire connects with the Neutral Terminal on the IQ
Data's chassis. (See Figure 2. 1A.)
Switch
SW2, No.
8
must be set to correspond to the chosen
wiring configuration. Set this switch to the:
•
OFF position for a 4-wire wiring configuration
•
ON position for a 3-wire wiring configuration
When the OFF position is selected for the 3-wire configuration,
the Display Window does not display the 3 line-to-neutral
AC
line measurements of the Operator Panel's menu. The
measurements not displayed are:
•
VA-N Volts RMS
•
V
s-N
Volts RMS
•
V C-N Volts RMS
5.1.6 AC Line Voltage-
The
10
Data can be set to meas
ure AC line voltage in one of two ways:
21
IQ DATA
•
Line-to-line - 3 Phase 3 Wire
•
Line-to-neutral - 3 Phase 4 Wire
Table 5.8
PT RATIO SET TINGS
SW2
Switch Settings
PT
Ratio
1
2
3
4
1: 1
(1)
ON
ON
ON
ON
2:1
OFF
ON
ON
ON
4: 1
ON
OFF
ON
ON
5:1
OFF
OFF
ON
ON
20:1
ON
ON
OFF
ON
30:1
OFF
ON
OFF
ON
35: 1
ON
OFF
OFF
ON
40:1
OFF
OFF
OFF
ON
55: 1
ON
ON
ON
OFF
60:1
OFF
ON
ON
OFF
70:1
ON
OFF
ON
OFF
100:1
OFF
OFF
ON
OFF
120:1
ON
ON
OFF
OFF
120:1
ON
ON
OFF
OFF
Any other combinations
(1l
Required setting when no
PT
used.
Note that the settings of these potential transformers' switches
allow the IQ Data to calculate and display the original, un
reduced line voltage even though the level at the AC Line Con
nection Terminals is reduced with an external potential
transformer.
5.1.7 Display Volts-
The
3
A
C line-to-line voltages and the
3 AC line-to-neutral voltages which appear in the Display Win
dow are auto ranged to represent units of kilovolts or volts.
Shaded area designates information that
replaces or supplements applications using
the 3-phase Power Module.
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