Current Peak Limiter (Cpl); Power Average Limiter (Pal); Current Average Limiter (Cal); Voltage Clip Limiter (Vcl) - Lab.gruppen PLM Series Operation Manual

7 OPERATION AND PERFORMANCE

7.3.2 Current Peak Limiter (CPL)

The output Current Peak Limiter (CPL) ensures that
the power output section will not be damaged by
forcing it to deliver current levels at the outputs that
exceed the maximum current ratings of the output
transistors. The CPL keeps the output transistors
within their Safe Operating Area (SOA). The CPL is
non-adjustable.
CPL activity is indicated by the affected output channel
LED (one of the four LEDs in the soft function buttons
to the right of the display) flashing red together with
a CURRENT CLIP warning message displayed on
the screen adjacent to the LED. A warning is also
displayed on the controlling PC via the network.
This condition indicates an attempt to draw excessive
current at the output. The output is attenuated until
the output current falls below the maximum current
rating. (See section 13 – Technical Specifications for
further details concerning ratings.)
If excessive current is indicated, check the
output cables and examine the loudspeaker.
If impedance appears to be normal, you
may rectify the condition by altering the
ISVPL settings or lowering input levels. CPL indication
can be triggered by excessively low output impedance,
possibly the result of too many loudspeaker cabinets
connected in parallel.

7.3.3 Power Average Limiter (PAL)

The Power Average Limiter (PAL) controls the AC
current into the power supply. Power consumption
is limited to the rated design parameters of the
power supply, ensuring that the PSU will never be
overloaded. Also, high-power products such as those
in the PLM Series can potentially draw more current
(with output devices still within safe operating areas)
than is allowed by the mains fuse.
Only the 230 V version is fitted with a fuse.
It is not possible to source fuses with sufficient
current capacity for the 115 V versions.
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.
20 PLM Series Operation Manual
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 DLC
PLM Edition software.

7.3.4 Current Average Limiter (CAL)

The Current Average Limiter (CAL) monitors the RMS
current drawn from each 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 DLC
PLM Edition 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.
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 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.
In either case, a report is also sent via the control
network to the DLC PLM Edition 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 DLC PLM
Edition software.