Main > Everything Else
New Project involving old water pump motor
danny_galaga:
--- Quote from: Ken Layton on July 09, 2008, 12:00:37 pm ---During startup, an electric motor can easily draw double the current than what it normally operates on.
--- End quote ---
can be way more. i know that a truck starter that draws say 100A while cranking, can draw over 500A for the first .25 second anyway. and to test it you apply a dummy load. it could be drawing closer to 1000A for several seconds!
TOK:
Kind of a hypothetical question, but something you can do with a scooter that you can't do with a regular electric motor... If you push it forward a bit manually before applying power which starts spinning the motor, does it lessen the startup draw?
As an example, think of an R/C car with an almost dead battery, it can't overcome its own mass if you apply power, but if you push it forward lightly and apply power, it can have enough to keep moving for a pretty long time.
danny_galaga:
--- Quote from: TOK on July 10, 2008, 05:59:41 am ---Kind of a hypothetical question, but something you can do with a scooter that you can't do with a regular electric motor... If you push it forward a bit manually before applying power which starts spinning the motor, does it lessen the startup draw?
As an example, think of an R/C car with an almost dead battery, it can't overcome its own mass if you apply power, but if you push it forward lightly and apply power, it can have enough to keep moving for a pretty long time.
--- End quote ---
exactly right. a series wound motor at rest draws a huge amount of current. this is why they have full torque from zero rpm. the current draw is directly proportional to the rpm, the faster its spinning, the less current it draws. i guess you could say it approximates infinity- zero rpm= infinitly high current. infinite rpm = zero current draw. its not true in real life of course.
basically it boils down to the fact that its effective resistance is higher at speed because of back EMF (the fact that as a motor spins, it is also generating a current, which somewhat offsets the current it is drawing). coincidentally, the fact that the motor generates current from spinning is the basis for regenerative braking.
so yes, giving the scooter a 'push start' means the effective rpm isnt at its lowest. if you always push started this electric scooter, you would greatly increase its range...
Ummon:
I think the largest point here is gourami doesn't know the basest of these technical details to start this project. Ideas are fine, but often won't get ya far on their own.
danny_galaga:
yeah, but its not a HUGE project. i say have a crack at it Gourami! that or something else fun...
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version