Current Average Limiter (Cal ™ ); Voltage Clip Limiter (Vcl); Temperature Protection; Dc Protection - Lab.gruppen PLM series Operation Manual

7. Operation and Performance
The PAL protection feature can help prevent the supply's external breaker from tripping within time intervals
of less than three minutes. For longer time intervals, it is the responsibility of the user to ensure that the
average level of the audio is within limits that ensure that the breaker doesn't trip.
PAL activity is indicated by the LED within the first soft button adjacent to the display flashing red, together
with a PAL ACTIVE warning message displayed on the screen. A warning is also displayed on the Lake
Controller software.
7.3.4 Current Average Limiter (CAL )
™
The Current Average Limiter (CAL) monitors the RMS current drawn from each power output channel to
ensure that the power output stages are not overloaded. When activated, it regulates the current to a safe
level to protect the channel. The CAL should not be activated in normal usage, but if it is, its operation
is indicated by an active LED and the message CAL ACTIVE. Further indication is given within the Lake
Controller software.

7.3.5 Voltage Clip Limiter (VCL)

If current draw from the PLM's power supply is too high, the PSU's regulation capability may be exceeded
and the internal voltage rails may drop. This can cause clipping; if this occurs the Voltage Clip Limiter acts
rapidly to prevent clipping occuring on the subsequent peaks. Indication of this condition is shown on the
output LEDs.

7.3.6 Temperature protection

Thermal measurements are made at several points within each channel as well as on the power supply or
the DSP area. If the maximum permitted temperature is exceeded, a high temperature warning is given. In
the case of an amplifier component overheating, this will be indicated by one of the power output channel
LEDs (in the right-hand soft function buttons) showing steady red. The adjacent fault message will show
TEMP FLT:CH. In the case of the PSU overheating, the fault is indicated by the top left soft button's LED
turning steady red, and the adjacent on-screen text displaying the fault message TEMP FLT:PSU or TEMP
FLT:DSP respectively. In either case, a report is also sent via the control network to the Lake Controller
software.
However, before the monitored components reach their maximum permitted temperature, a warning is
given by the appropriate LEDs (as above) first turning yellow and an adjacent warning message TEMP
WARN:CH being displayed. Again, a corresponding message is sent via the network to the Lake Controller
software.
If a power output channel temperature fault condition arises, the output of the channel causing the condi-
tion will be muted. Temperature checking will continue thereafter at 0.5 second intervals, with the output
remaining muted until the fault condition clears.

7.3.7 DC protection

DC protection is implemented on each power output to prevent damage to connected loudspeakers or any
PLM components. DC present at the output will cause the PLM's power output module fuse to blow. In this
instance a red LED will illuminate and the message "Needs service" will be displayed.
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PLM Series Operation Manual rev 1.1.3