diode loss

[thirteen]

My nieghbor emailed me and asked me if a diode could leak when it is cold? He has a 48 volt system and is powered by hydro. He was spring cleaning everything on his turbine and when he moved some of his wires he saw his meter flicker where it was attached. There was no water flowing and the line is coming from the battery bank to the controler then thru the diode then to the turbine. The turbine was disconnected . He showed .01 volts for several seconds and then it stopped. He hooked everything back up and does not have any problems that he can find. The ones I've dealt with are either working or not.

[DamonHD]

For a normal silicon diode/rectifier leakage is tiny, and is further reduced when cold.

Much more likely something else going on, such as damage or damp or failing insulation or radio noise getting coupled into the meter or leprechauns.

Rgds

Damon

[Flux]

There is always a leakage current with a reversed biased diode, but for a silicon diode it is tiny. With a hydro set up you could easily have more surface leakage from damp components than from a good diode. Even so if measuring volts with a multimeter with turbine disconnected you will quite likely see a reading. the input impedance of the average multimeter is 10mohms so a few micro amps will give some reading.

Leakages under a milliamp will be of no consequence so this test is unrealistic. If you shunt the meter with a 1k resistor and still measure significant volts then it might be an issue.

Flux

[thirteen]

I'll relay this information to him. He has not had any problems for the last 4 years. Thank you for the information.