Lab.gruppen PLM 20000Q - Manual (Page 31)

Operation and Performance
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PLM Series Operation Manual rev 1.2.3
5.3.11 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.
5.4 Power Supply
The R.SMPS (Regulated Switch Mode Power Supply) is designed to keep supply voltage rails at optimum
levels even when the mains voltage drops. 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 a clean LF response.
The PLM 20000Q is also equipped with a universal power supply with power factor correction (PFC). The
device can take any mains voltage, from 65 V to 265 V, allowing it to function worldwide in many different
configurations. The PFC reduces current peaks on the lines and reduces the requirements placed on the
mains distribution system. The PLM 20000Q has an unparalleled power factor extremely close to one.
5.4.1 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 insufficient power is available to allow simultane-
ous power-up, then there is probably insufficient
capacity for full power output during operation. It is
recommended that additional capacity is added to
the mains power distribution system.