CCR961 MANUAL-GB
35
Version B2:01-07-2015
3.13 Control of transformer tapping
Selection of the correct tapping on the output transformer can be based on a number of different
criteria’s, such as expected variations on the mains supply etc. See the special document for more
details.
Below is given some simple guidelines for the control of the tapping or in connection with the
change of tapping.
With the CCR in ”Normal Menu 1, N1”, where current and step are given, you can press the push-
button
←
and see the following figures: 10/(500 – XXX).
The figure XXX is an expression for the time delay in each half wave before the thyristors are
activated, and in this way an expression for the regulation reserve when the CCR is in the 100%
step.
We can recommend the following values for the figure XXX:
CCR size (KVA)
Isolating transformer nominal power (VA)
≤
100 >100
0 – 2,2
230 – 250
250- 280
2,2 – 5
160 – 200
180 – 220
7,5 – 12,5
150 – 190
160 – 200
≥
15
140 - 180
150 – 190
If the figure XXXX is too high, a lower tapping must be selected, if possible.
For very small CCR ratings, it might be necessary to increase the XXXX value, as a faulty lamp
could cause an Imin alarm.
Tapping:
Tapping means changing the maximum output power of the CCR, by connecting the series circuit
to a lower secondary output tapping than the maximum.
From factory, the CCR’s will always be shipped connected to full output rating.
Dependent of type and power rating, the output transformers are supplied with tapping possibility
in steps of 10% (three output terminals / coil) or with tapping possibility in steps of 7,5% (four
output terminals / coil).
On the following page are diagram 961.906BL, showing the wiring in the CCR cubicle.
In the top of the drawing is shown box simulating the CCR module.
Top, right shows the Remote control terminals (-XX1).
In the middle the current measuring transformer (-XT1) and the ISO box (-XE1)
Below the output transformer, with the secondary terminals to –XX4, where the tapping is
done.
To the right you will find two tables.
o
The top one valid for transformers with 7,5% tapping steps
o
The lower one valid for transformers with 10% tapping steps
On –XX4 the series circuit is connected to the output transformer via S1 and S2, in this case to
5 and 12.
The two secondary windings (one / coil) is connected in series by means of the current
measuring transformer –XT1, in this case between 8 and 9.
I we look at the top table, it can be seen that the use of shown connections will give 100%
output voltage.
In the table, it can be seen how to connect to get lower tappings.
