This post is for the electric go cart project I'm brewing up (bought a rolling frame today, it's UGLY 50$!)
I think I want about 20hp worth of motor on it. I can get 2 10hp motors for much cheaper (and lighter weight) than I can get one 20hp motor.
I've seen already here that mechanically coupling and electrically paralleling brushed DC motors results in one motor (the one with the least resistance) taking the bulk of the electrical power, to the point of melting. I am wondering, Assuming 2 identical (not perfect world "identical", but same model bought from the same place at the same time) motors are coupled to a shaft and provided the same PWM duty cycle; if by using 2 seperate controllers (or 2 seperate banks of FETs in the same controller) for 2 motors, and mechanically coupling them, would they share a load evenly? Well, this makes me think that if they are both receiving identical PWM, then functionally they are still in parallel, just with seperate switches between the motors and ground and would encounter the same problem.
Another idea: what if on one motor (call it master motor) the PWM duty cycle is controlled by the accelerator, and the the duty cycle for the second motor (call it slave motor) is controlled to maintain a match of the current measured on the first motor?
Anybody have any wisdom to share about load sharing with DC brushed motors? I have a feeling it's doable but probably a lot trickier than first thought.
one question, on the theory of it; which of the following 2 statements are the closest to being true?
1. If the 2 motors aren't putting out the exact same torque at the same time, then the lower torque motor is actually acting as a load on the higher torque motor and slowing it down, not helping it. (I.E. motor 1 is putting out 100 ft*lbs of torque, motor 2 is putting out 75ft*lbs; total torque is 75ft*lbs) Chain is only as strong as it's weakest link.
2. If the 2 motors aren't putting out the exact same torque at the same time, then the lower torque motor is adding to total torque, but to a lesser degree than it could be if they were matched.(I.E. motor 1 is putting out 100 ft*lbs of torque, motor 2 is putting out 75ft*lbs; total torque is 175ft*lbs)
I think I want about 20hp worth of motor on it. I can get 2 10hp motors for much cheaper (and lighter weight) than I can get one 20hp motor.
I've seen already here that mechanically coupling and electrically paralleling brushed DC motors results in one motor (the one with the least resistance) taking the bulk of the electrical power, to the point of melting. I am wondering, Assuming 2 identical (not perfect world "identical", but same model bought from the same place at the same time) motors are coupled to a shaft and provided the same PWM duty cycle; if by using 2 seperate controllers (or 2 seperate banks of FETs in the same controller) for 2 motors, and mechanically coupling them, would they share a load evenly? Well, this makes me think that if they are both receiving identical PWM, then functionally they are still in parallel, just with seperate switches between the motors and ground and would encounter the same problem.
Another idea: what if on one motor (call it master motor) the PWM duty cycle is controlled by the accelerator, and the the duty cycle for the second motor (call it slave motor) is controlled to maintain a match of the current measured on the first motor?
Anybody have any wisdom to share about load sharing with DC brushed motors? I have a feeling it's doable but probably a lot trickier than first thought.
one question, on the theory of it; which of the following 2 statements are the closest to being true?
1. If the 2 motors aren't putting out the exact same torque at the same time, then the lower torque motor is actually acting as a load on the higher torque motor and slowing it down, not helping it. (I.E. motor 1 is putting out 100 ft*lbs of torque, motor 2 is putting out 75ft*lbs; total torque is 75ft*lbs) Chain is only as strong as it's weakest link.
2. If the 2 motors aren't putting out the exact same torque at the same time, then the lower torque motor is adding to total torque, but to a lesser degree than it could be if they were matched.(I.E. motor 1 is putting out 100 ft*lbs of torque, motor 2 is putting out 75ft*lbs; total torque is 175ft*lbs)