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

7 OPERATION AND PERFORMANCE
for details.) Note that the maximum ISVPL setting
of 153 V is greater than the 150 V maximum peak
voltage available from the example PLM 10000Q.
Other models may differ. This is to accommodate
the small degree of production spread of maximum
output voltage that exists between PLMs. By
allowing a maximum ISVPL setting fractionally higher
than the maximum safe output voltage under any
condition ensures that severe clipping will never be
encountered.

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 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 this fault condition is indicated, check the
output cables and examine the state of the
loudspeaker. If there appears to be a normal
impedance present, it may be possible to
rectify the condition by altering the ISVPL settings
or lowering the input levels. CPL operation may also
be occasioned by too low an output impedance, as
would be caused by too many loudspeaker cabinets
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
20 PLM Series Operation Manual
(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.
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. Futher 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.

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 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