VFD Questions

Rube Goldberg might be impressed, but I think this scheme slices/dices/unslices/undices energy too many times to be efficient.

Is there a new scheme for Mech-E?? Make them electrical engineers first [like Mr Royce of Rolls-Royce] and they will do a good job with the Mech-stuff!! By the time you get your "Emmett" scheme working, you will be Elec-E - but do you have the time!! My limited knowledge of "electro-active" materials suggests they change shape when you apply a DC voltage. My limited knowledge of penguins and whales suggests they do not flap their "wings" like humming birds - so for water I guess switching a battery polarity at hand control rates would be OK for "proof of concept". Since you have written nothing about the voltages, currents and frequencies needed to drive the fins, one can do little to help. VFD drives are designed to drive metal windings on magnetic materials - is there any similarity with your "electric muscle"??

Absolutely agree, hysteresis alone would render these fins useless, they can't respond to fast current changes.

Too many energy conversions (with a loss at each stage) will kill the design as well.

I can't provide any advice on this.

I would ask the O.P. if he can switch to a "body driven" stepper motor, with its windings connected to another stepper motor, and have the later move a conventional propeller?

Yahlasit

In the old days when I was in college, as a dual Physics Major / EE I got a job grading Mech E tests from a surface physics course for EE's taught by a Mech E Prof. The Mech E department was heavy into semiconductors????? Good money for a student - no questions asked. I see nothing much has changed in 35 years.

Hey Mr. ME student!

Do your own homework first. If your initial desired direction is to have the human generate electricity with an alternator, I think you must first solve the mechanical power equations. Determine how much mechanical power your fins can create, how much electrical power it takes to do that, then investigate how much power a human can generate with an alternator, then solve for losses through all components in the system. You may discover you have some serious issues to overcome long before you get to the point where a power controller, and its additional associated losses, is ready to be added into the equation.

But from an electrical engineering standpoint, I think what you need is a simple square-wave generator, an old technology no longer used in VFDs. Modern VFDs are not optimized to control AC induction machines, and I don't believe electro-active polymers will constitute an inductive load. Some cheap UPS systems still use square-wave outputs, albeit not variable. You might be able to modify one of those or find an EE student friend to do a joint venture with you and make your own.

Wouldn't a 21-speed derailler gear system be more efficient?