The electronic alternative to emergency Engine

risk management

twistedtree said:

I'm far from an expert, but my understanding is that most large variable speed electric motors are AC, controlled by variable frequency drives. They are essentially inverters where you can control the frequency and voltage to control the speed of an AC motor. Large thrusters, propulsion motors, trains, and electric cars all work this way, as I understand.

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The installed base of railed traction motors are primarily DC. Series wound DC motors, not requiring electronics for control. More modern implementations (hi-speed rail, etc) are AC motors driven by IGBT semiconductors; ie, variable frequency drives. AC motors enjoy brushless, no commutators, lower MOTOR maintenance. At the risk of lower control reliability.

I'm a newcomer to this thread; but it would seem reasonable to someone in the know to list the primary faults one is trying to mitigate with this emergency get-home system.

A list like this:

1) out of fuel
2) prop/shaft fouled
3) loss of controls
4) fused semiconductors in the prime mover due to lightning
5) loss of lube oil in the prime mover
6) shaft breakage
7) contaminated fuel
8) grounding damage
9) transmission clutch damage/slipping


If done in a top to bottom order of likelihood, I do believe this would help on choosing a get-home solution.

I'm been aboard some very large vessels, operating with risky cargo, far from port, with just one prime mover and no secondary. It comes down to acceptable reliability. Two engines, a generator can and do die simultaneously with one lightning hit. A single steam engine won't.
Maybe this is generally an unsolvable equation for a sub 100' boat, not sure.