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Stuck Starter Contactor - Lesson to learn

Myself only a lowly toolmaker, no electrickery guy, I´d think any voltage drop by a SSR looks minimal compared to the drop by high amps from the starter, more than just 2 V I´d say. One can ponder a lot about adverse effects – or lack of any, who knows. I would give it a try and spend € 15.- if I felt the need to find out. My bit of knowledge about thyristors is they don´t switch off with DC once conducting, so only used in AC loads. So in a DC-DC relay I guess any other type of semiconductor is in there. Like in modern welding equipment no more tons of coils, just a collection of power chips for hundreds of amps in a 15 kg machine. Just thinking, voltage drops with these SSRs should be a concern anywhere installed so maybe that effect is overrated and really no factor anywhere? In a 28 V system a starter motor will have the battery voltage come down maybe one third anyway under load, so who would know the SSR contribution ? A test would be revealing, also in regards to voltage spikes. Voltage spikes from semiconductors – or the motor ?? Is there anything at all in such a setup , I don´t know ?? Again, a test would tell and at € 15.- or so I´d throw one or two into the toolbox , cheap and no weight – a criterium for me to accept any electronics anyway, else I´d prefer the more mechanic electric systems for sure – so no electronic ignition in my aircraft !!! Reliable well built magnetos like the Russian types are our choice instead. OK, allright, today the coils in there have grown a bit old so no great idea to go flying with old stock. @ canuck, yes, the buzzer coil in the 18 T failed many years ago, so I found NOS military supply German Prüfrex buzzer coils in Ebay and that was that. And yes, we have the small lever on the electric air valve for the air starter, no problem. Vic

Yes very true about thyristors and DC. These chinese DC SSRs probably use IGBTs, looking at the 2V drop spec.

Shoreham EGKA, United Kingdom

Heavy use of the starter without engine starting often causes solenoids to stick. as already mentioned, the heat generated from the current will happily weld the contacts together, often to the point where even the “tapometer” doesn’t resolve the situation.

Forever learning
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