Hi all. Suppose I had a robot motor rated for 12V that put out whatever amount of torque and speed. This is just fine when the robot is climbing something like stairs or a rock pile, but leaves speed to be desired when the robot is just cruising on relatively flat terrain.
I cannot use a bigger motor, and I cannot use a faster, higher power motor of the same size since I cannot easily add any more gearing (and I don't want those extra transmission losses). I was thinking that I could run the motor off of an 18V battery. During climbing when load (and current) are highest, I would limit the PWM duty cycle so that the motor effectively sees rated voltage. But during cruising when current draw is less, I would run the motor on the full overvolted battery voltage to get more speed.
THis would be accomplished by monitoring the current and always keeping it below the rated motor current (at 12V) so when current increases during climbing, it's limited so the motor won't burnout, but when the load is low, the current is increased (via overvolt increase) so that the speed would be higher.
Does anyone see anything wrong with this? Running a motor at higher voltage, but limiting the PWM duty cycle so it "sees" rated voltage when it is most likely to burn out (I'm thinking there may be problems that arise from the fact that a during PWM overvolt pulses are still applied to the motor so the voltage at the motor is actually above rated)? These are RC truck motors so I am not sure what they rate the insulation breakdown as (would it be higher than several times rated voltage? Or would it just be 2 or 3? or even less?). Or do I not even have to worry about breakdown voltage since the voltage is so low and they are probably using standard wire which is rated at 100V or higher? I've also read that smaller motors (like these ones) are sensitive to overvolting (if it's even possible, I do not know).
Does the life a 12V motor decrease when you run it from a 24V supply but you are only running it at a PWM duty cycle of 50% max? The current the motor gets is the same as if a 12V battery was used, but during PWM 24V pulses are is still being applied to the motor.
THanks.
I cannot use a bigger motor, and I cannot use a faster, higher power motor of the same size since I cannot easily add any more gearing (and I don't want those extra transmission losses). I was thinking that I could run the motor off of an 18V battery. During climbing when load (and current) are highest, I would limit the PWM duty cycle so that the motor effectively sees rated voltage. But during cruising when current draw is less, I would run the motor on the full overvolted battery voltage to get more speed.
THis would be accomplished by monitoring the current and always keeping it below the rated motor current (at 12V) so when current increases during climbing, it's limited so the motor won't burnout, but when the load is low, the current is increased (via overvolt increase) so that the speed would be higher.
Does anyone see anything wrong with this? Running a motor at higher voltage, but limiting the PWM duty cycle so it "sees" rated voltage when it is most likely to burn out (I'm thinking there may be problems that arise from the fact that a during PWM overvolt pulses are still applied to the motor so the voltage at the motor is actually above rated)? These are RC truck motors so I am not sure what they rate the insulation breakdown as (would it be higher than several times rated voltage? Or would it just be 2 or 3? or even less?). Or do I not even have to worry about breakdown voltage since the voltage is so low and they are probably using standard wire which is rated at 100V or higher? I've also read that smaller motors (like these ones) are sensitive to overvolting (if it's even possible, I do not know).
Does the life a 12V motor decrease when you run it from a 24V supply but you are only running it at a PWM duty cycle of 50% max? The current the motor gets is the same as if a 12V battery was used, but during PWM 24V pulses are is still being applied to the motor.
THanks.
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