28
REVO S
3PH from 300A to 800A
User’s manual
Heater Break alarm and SCR short circuit
(HB
Option only)
Caution:
to work properly the load must be powered at least about 160msec.
The Heater Break circuit read the load current with an Internal current transformer (C.T.).
Minimum current is 10% of the current transformer size.
If load current is below this value the Heater Break Alarm doesn’t work properly.
7.1 Heater break Calibration procedure
An automatic function sets the Heater Break Alarm.
The auto setting function can be activated by pressing the keys
+
simultaneously for 4 seconds.
The Heater Break calibration procedure is performed in this way:
• The Unit gives the maximum voltage output
• The leds light up in sequence until the procedure is completed
• The current and voltage value is stored in memory
• After about 15 second the unit comes back to the initial situation
If load resistance increase more than 20% (sensitivity 20%) the HB LED become ON and alarm relay change
status.
If the unit is still in conduction with no input signal (ON LED OFF) it means that there is a short circuit on
thyristors and SC LED become ON.
If the load has been changed the Heater Break calibration procedure must be done again.
The HB Alarm is detected with minimum ON time 100 ms
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