Lab.gruppen PLM 20K44 Operation Manual

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Lab.gruppen PLM 20K44 Operation Manual Manual pdf 25 page image

5. Operation and performancePLM+ SERIES Operation Manual rev 3.0.1255.4.1. Low Inrush CurrentHigh power amplifiers with inadequate inrush current limiting can draw considerable current from the mains atturn–on, sometimes tripping a fast–acting mains breaker. The PLM+, however, has very low inrush current toprevent tripping of breakers. Several units can, under normal conditions, be powered up simultaneously. If youdo experience problems powering up multiple units simultaneously, they must either be turned on manually in anordered manner, or sequenced remotely using the Lake Controller software’s Global Control feature. Alternatively,the capacity of the mains supply should be increased.NOTE: If insufficient power is available to allow simultaneous power–up, then there is probablyinsufficient capacity for full power output during operation. It is recommended that additional capacity isadded to the mains power distribution system.5.5. LoadPilot Load Monitoring5.5.1. IntroductionLoadPilot is a feature in PLM+ amplifiers that can continually monitor the integrity of loudspeakers and cablesconnected to the outputs to ensure that they are functioning properly and free from major anomalies or faults.By implementing LoadPilot, systems incorporating PLM+ amplifiers can be certified in compliance with voiceevacuation standards such as EN54–16 and NFPA72.LoadPilot functions by automatically superimposing low–level pilot tones on the input signal (if any present) to theamplifier. One tone is below the range of human hearing (approximately 10–20 Hz) and the other above (24 kHz),so the activity of LoadPilot is inaudible regardless of whether the system is currently reproducing program content.High–resolution current sensing on the outputs can calculate the impedance of the load at the frequency of thetones. Hence a stable measurement of the impedance of the load can be obtained and potential anomalies orfaults can be detected that would indicate impaired loudspeaker function or total inoperability due to failure of theloudspeaker or faults in connected wiring. The superimposition of pilot tones and analysis is interleaved across theamplifier’s output channels with a maximum total cycle time of around 20 seconds.LoadPilot is implemented and configured in the CAFÉ software. Monitoring status and fault indication are displayedon the front panel and both in CAFÉ and Lake Controller.LoadPilot may be configured with the automatic calibration or through a manual advanced mode, depending onmonitoring requirements and characteristics of the connected loudspeaker loads.5.5.2. Automatic calibration5.5.2.1 Functional descriptionAutomatic calibration is suitable for the following applications and requirements for error detection:• If one or two low–impedance loudspeakers are connected; if two in parallel is default, it will warn if one ismissing.