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Separate master and alternator switches?
- Thread starter rockitdoc
- Start date
Ok. What is an OV crowbar design?
See https://www.periheliondesign.com/lovm.htm
It's a neat little sensor that will kill the alternator output and prevent an overvoltage condition from cooking everything.
RockitDoc,
You can use a double-pole double-throw (DPDT) switch to handle switching the master solenoid on one pole and the alternator field with the other.
As a side note, the Perihelion Over Voltage device does not use the "Crowbar" technique. It opens or closes a relay upon an over-voltage event. (Then you decide what to do with those relay contacts.)
The Crowbar technique actually causes a short circuit (hence "crowbar") across the regulator circuit breaker and pops the breaker, upon detecting over-voltage. I know it sounds a little scary but is a clever, and perfectly acceptable, solution to the problem of shutting-down an errant regulator.
Also, GYoung makes a good point. Some regulators require their power to be cycled to reset and you would not want to turn-off the master in flight to reset the alternator (as would happen if you used a single switch).
The short answer is: use a pull-able 5 amp circuit-breaker (like Potter Brumfield W23 series) and the DPDT switch like I described in the first paragraph and everything will be good. This configuration accomplishes several things:
1. Allows you to kill/reset the alternator by pulling the breaker
2. Control the alternator field and master solenoid with a single switch
3. Allows for the use of a Crowbar Over Voltage module, if desired
BTW, this is a very common setup
You can use a double-pole double-throw (DPDT) switch to handle switching the master solenoid on one pole and the alternator field with the other.
As a side note, the Perihelion Over Voltage device does not use the "Crowbar" technique. It opens or closes a relay upon an over-voltage event. (Then you decide what to do with those relay contacts.)
The Crowbar technique actually causes a short circuit (hence "crowbar") across the regulator circuit breaker and pops the breaker, upon detecting over-voltage. I know it sounds a little scary but is a clever, and perfectly acceptable, solution to the problem of shutting-down an errant regulator.
Also, GYoung makes a good point. Some regulators require their power to be cycled to reset and you would not want to turn-off the master in flight to reset the alternator (as would happen if you used a single switch).
The short answer is: use a pull-able 5 amp circuit-breaker (like Potter Brumfield W23 series) and the DPDT switch like I described in the first paragraph and everything will be good. This configuration accomplishes several things:
1. Allows you to kill/reset the alternator by pulling the breaker
2. Control the alternator field and master solenoid with a single switch
3. Allows for the use of a Crowbar Over Voltage module, if desired
BTW, this is a very common setup
