Current Peak Limiter (Cpl); Power Average Limiter (Pal) - Lab.gruppen PLM series Operation Manual

7. Operation and Performance
* Note that these ratings are limited by the CPL (Current Peak Limiter) functions, not by ISVPL settings, due to
amplifier channel current capacity.
The ISVPL threshold may be set at any level between 17.8 V and 193 V via the PLM's menu system. (See
Section 9.12.2.5.1 or the Lake Controller User Manual PLM Addendum for details.) Even PLM model's that
have a smaller peak output voltage can set the ISVPL threshold all the way up to 193 V. When a threshold
is set above the maximum capability of that model, the actual internal value will be limited to that models
internal ISVPL maximum. Hence the ISVPL threshold can be configured in Modules to protect at the
speaker maximum capabilities and the Module file is still cross-compatible with all PLM models. Note
that the maximum internal ISVPL setting of a particular model is greater than the 150 V maximum peak
voltage available from that model. Typically the internal maximum ISVPL Threshold allows for an overshoot
of 3V compared to that model's maximum peak output voltage. This is to accommodate the small degree
of production spread of maximum output voltage that exists between PLMs. 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 on the power output channel LED (one of the four LEDs in the soft function buttons
to the right of the display). Activity on an affected channel results in a flashing red indication 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.
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PLM Series Operation Manual rev 1.1.3