my original thoughts centered around no belts to break, being able to decouple the motors in the case of a problem 50% of the time and direct connecting because of the constant torque that a motor provides.... others reminded me that the motors would operate more efficiently if they were allowed to reasonably spin up and that cooling would be better served by spinning up.... just thought it interesting that motors had been doubled up
as a sort of corollary question to my original one, IF an electric motor can, for arguments sake, utilize 100 amps at a given voltage but never uses more than 30amps because that provides so acceptably close to hull speed then isn't that motor over sized by more than two times? Wouldn't it be better to have half the motor as such a motor only only being able to absorb 50amps would be no detriment at all at the same power level of 30amps. Isn't 30amps at a certain voltage delivering the exact same power regardless of whether the motor could ultimately handle 50, 100 or 500amps. I realize that inertia and other factors would have a part to play but don't these other factors all tend to point to the use of the smaller motor rather than the larger?
From: Ed Bachmann edbz <edbz@hotmail.com>
To: electricboats@yahoogroups.com
Sent: Friday, September 9, 2011 8:58 PM
Subject: Re: [Electric Boats] Re: why you don't want to oversize electric propulsion motors...
Why couple the two motors together like the EY 360ibl when the big desired benefit for two motors and two controllers is redundancy?
How about mounting the motors so each links to the drive shaft via its own belt drive? Design the belt tensioning method to allow either motor to be disconnected easily. Or, in an emergency, a knife could be used for a fast disconnect.
Ed B
From: Eric
Sent: Friday, September 09, 2011 9:05 PM
Subject: [Electric Boats] Re: why you don't want to oversize electric propulsion motors...
Coupling two motors together is not uncommon. But like we discussed before, you still need two controllers. And you still would need some sort of reduction if you wanted your motors to spin faster than the propeller shaft. Hey, that sounds just like an EY 360ibl... ;) If you're thinking about direct drive, they would be just like the Solomon Technologies motors. (now that I've watched the videos, they are Solomon motors)
His theory that running two 4.5kW motors instead of the 9kW motors would increase his regen capabilities may not play out in the real world. This sounds like a case where experimentation would be needed to support that premise. I can't believe that his regen would double for the same sailing speeds. He does seem to have a lot of interesting things to say, but I think that he plays a little fast and loose with specific data. It does make a good story though...
Eric
His theory that running two 4.5kW motors instead of the 9kW motors would increase his regen capabilities may not play out in the real world. This sounds like a case where experimentation would be needed to support that premise. I can't believe that his regen would double for the same sailing speeds. He does seem to have a lot of interesting things to say, but I think that he plays a little fast and loose with specific data. It does make a good story though...
Eric
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