Eurotherm 7000 Series, Руководство пользователя

Страница: 50 / 69

7300A User Manual 5-5
Alarms
5.3.1. Setting the DLFalarm
This can be set using the push button on the front panel. The PLF detection setting can only
be adjusted (reference impedance recalculated) in the following conditions :
• rms voltage across load is greater than 40 % of the nominal voltage
• rms current is greater than 30% of the rated current
• no over-temperature or thyristor short-circuit faults.
• each time PLF setting is required the three-phase load must be balanced.
• in order to guarantee the full scale sensitivity, settings must be done at the load’s nominal
temperature
Note : PLF settings stay memorised even if a supply cut-out occured
5.3.2. Partial or Total Load Failure Detection
PLF detection is only possible under the following conditions :
• no over-temperature or thyristor short-circuit faults.
• rms voltage across the load greater than 40% of the nominal voltage and,
• rms load current greater than 5% of the rated current.
Total Load Failure TLF monitoring is only possible under the following conditions :
• no over-temperature or thyristor short-circuit faults.
• the rms voltage across load is greater than 40 % of the nominal voltage
5.3.3. Partial Load Failure Detection Sensitivity
Partial Load Failure Detection Sensitivity can be expressed in terms of a maximum
number of load elements connected in parallel for which the unit can detect the failure of
one element. The DLF sensitivity guaranted for identical three-phase loads connected in
parallel is :
3D coupling - 1 element out of 3
3S, 4S and 6D coupling - 1 element out of 4
5.4. Signalling of channel for load fault
With the ‘DLF’ option the DLF LED flashes in particular ways to indicate the number of
the controlled channel (of the three thyristor channels) on which load failure (TLF or PLF)
has occurred.
5.5. Load type matching
PLF detection is adapted to the load type.
The type of load controlled is selected when ordering, with the product code:
• LTCL (Low Temperature Coefficient Load), or
• SWIR (Short Wave InfraRed elements.
5.6. Disabling alarms for load failure signalling
PLF fault signalling (‘DLF’ indicator and relay) can be temporarily excluded from alarms by
pressing the ‘CHK / SET’ (Check / Setting) push button.
If the fault persists, DLF signalling returns to the alarm position.
If the ICO option is used, PLF and TLF faults can be excluded from alarms using the
external acknowledgement logic input.