RCDs for protecting 100V amplifier output

Jun 11, 2012 6 Replies

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Gerard 14 years ago

Hello all. I'm designing a paging call sysytem with 4 500W class D amplifiers which output 100V audio to loudspeakers in a refinery. I have the amplifiers and the relative Controller Network unit installed in a

600 x 600 x 42 rack unit cabinet. I have the mains voltages output to a multisocket units which I have protected with residual current devices. I was wondering whether it is possible and how so to protect the 100V output from the amplifiers which goes to the loudspeakers within the refinery. By this I mean the terminals in both the cabinet and the relative connections on the loudspeakers. I mean just in case anyone touches the terminals ... to avoid/minimize possible electrical shocks. Regards.

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Phil Allison 14 years ago

"Gerard"

** 100 volt speaker lines do not normally present a similar hazard to mains power - they have been around for many decades and the shock risk is minimal.

Very good idea to use a twin speaker cable that cannot be confused with AC power cable and use connectors on the line and cabinets that are touch proof - eg Amphenol PDN series.

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... Phil

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josephkk 14 years ago

Experimment with an ordinary GFCI. You might learn something.

?-)

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Jamie 14 years ago

And that lesson maybe the last one.. ;)

Jamie

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NT 14 years ago

If one really wants rcd action, a very low value resistor in each output wire plus a few opamps, and cut out the signal feed to the power amp if 20mA imbalance is found. Mostly simple, voltage range on the opamp inputs is where attention will be needed. A discrete stage could go between resistors and each opamp.

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NT 14 years ago

Cutting out would cause problems. Reducing output to keep leakage at a low safe level would be better, plus a latching warning light.

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josephkk 14 years ago

Only for someone that does not have enough sense to study up before experimenting and continues with ill considered experiments.

?-)

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