Dc Voltage Calibration - Gamatronic Centric 3x480 Vac User Manual

7.2.2.5

DC VOLTAGE CALIBRATION

This function is used to correct any inaccuracy in each module's measurement of its internal dc voltage.
(Note: a password may be required to complete this function.) Each module's readings are calibrated
before the UPS leaves the factory, but over time or due to environmental factors the Centric's dc
measurements may drift slightly.
Calibration of the dc voltage should be performed only under conditions where the UPS's input and output
currents and voltages are stable and not subject to fluctuation.
Dc voltage calibration must be performed on one module at a time, with all of the other modules turned off.
(To turn modules OFF, see section 7.3.1.3 "Operation > Switch on/off > MODULES OFF".) The reason for
this is that the updated values you enter get sent to all modules that are in the "ON" state, and you only
want them to affect the module being calibrated.
The readings for the positive and negative components of the module's dc voltage are calibrated separately
(but on the same screen), and can be increased or decreased separately.
To detect and correct any inaccuracy in the Centric's display of the battery voltage:
1. Turn off all but one module ("Main > Operation > Turn on/off"). We suggest you calibrate the modules
starting with the bottom-most module and working your way up.
2. On the rear side of the UPS, measure the voltage between the negative ("– " dc bus and midpoint bus
bar. See Figure 22. You would expect the value to be around 435 Vdc, ± 10 V.
3. Compare your measured value to the number to the right of the screen, which is the Centric's
measurement. If your measured value differs from the Centric's measured value, enter your
measured value into the field labeled "negative dc voltage" (see Figure 25).
4. Next, measure the voltage between the positive ("+") dc bus bar and the "N" dc bus bar. If your
measured value differs from the Centric's measured value, enter your measured value into the field
labeled "battery positive dc voltage".
5. Press the Confirm button to apply the corrected measurements.
6. Switch OFF the module just calibrated and switch ON the next module above it.
7. Perform steps 2 through 6 until all modules have been calibrated.
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AMATRONIC LECTRONIC
Figure 21: Dc voltage calibration
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CENTRIC 3x480, User Guide, rel. 1.7