digidocs
Joined: 04 Dec 2013
Posts: 59
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 Posted: Tue Jan 17, 2017 4:22 pm Post subject: DPST switch in place of split rocker master |
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Hi list,
I'm curious if there would be any negative consequences to using a standard SPDT toggle switch in lieu of the red split rocker or a progressive transfer toggleswitch. I already have a pullable breaker that can be used to shut down the (externally regulated) alternator in the rare case when that's desirable and I like the simplicity of just "on" and "off".
The only potential snag that has occurred to me thus far is that there could be a "load dump" event on switch off. This could happen because even though the field is disconnected at the same time as the battery, there is still stored energy in the alternator inductance that may take a few 100s of ms to dissipate. This energy would have to go to the bus as the battery would no longer be present to absorb it.
To some degree the progressive transfer mitigates this effect by sequencing the alternator field off first and then the master contactor. However, I'm not really sure how effective this is as the delay is probably quite small (<50ms?) and the alternator load dump pulse duration is accepted to be up to 400ms long (google ISO7637-2 Pulse 5). FWIW---my system is 24V and the unclamped load dump pulse could theoretically reach 200V according to the above standard.
Does anyone know if the red split rocker has any delay/sequencing built in or is it really just two switches that open simultaneously?
Thanks,
David
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