Short Circuit Protection; Power Supply - Lab.gruppen PLM series Operation Manual

mented solely to detect continuous VHF content. HF content of normal music or speech signals at peak
levels will be passed in full.
Operation of the VHF protection circuits is indicated by one (or more) of the output channel LEDs (in the
right-hand soft function buttons) showing steady red. The adjacent fault message will show VHF FAULT. It
is also reported as a fault via the control network.

7.3.9 Short circuit protection

A low impedance or short circuit at the power output terminals is detected when the output current is high
(Current Peak Limiter is active) and, simultaneously, the peak output voltage is below a predetermined
threshold (42 V with the PLM 10000Q, for example). When this situation occurs, the output stage is muted
to protect it from damage. Operation of the short circuit protection system is indicated by an output channel
LED (in the right-hand soft function buttons) showing steady red. The adjacent fault message will show
SHORT CIRCUIT. It is also reported as a fault via the control network to the Lake Controller software. The
presence of a short circuit (or low impedance) is re-tested every six seconds, and the output remains muted
until the fault clears.

7.4 Power Supply

The R.SMPS (Regulated Switch Mode Power Supply) is designed to keep supply voltage rails at optimum
levels even when mains voltages sag. Mains voltages can drop as much as 20% below nominal before there
is any effect on rail voltages. Thus the R.SMPS can deliver full rail voltage to the output stage at all times,
allowing the PLM to exhibit consistent transient response and undistorted LF response.
Low inrush current
High power amplifiers with inadequate inrush current limiting can draw considerable current from the mains
at turn-on, sometimes tripping a fast-acting mains breaker. The PLM, however, has very low inrush current
(the capacitors charge slowly and in a controlled manner) to prevent tripping of breakers.
Several PLMs can, under normal conditions, be powered up simultaneously. If you do experience problems
powering up multiple PLMs simultaneously, they must either be turned on manually in an ordered manner,
or sequenced remotely using the Lake Controller software's Global Control feature. Alternatively, the capac-
ity of the mains supply should be increased.
If the power distribution system in use has
insufficient capacity to allow simultaneous
power-up of all connected PLMs, then there is
probably insufficient capacity available to allow full
power output on all units during operation. In this case, it is
highly recommended that additional capacity be added to the
mains power distribution system.
7. Operation and Performance
PLM Series Operation Manual rev 1.1.3
31