I got my two motors from Tool-King for 99$ each and the shipping to Denmark for 70$ I talked with dewalt today and the 56nm is with the gearing in first gear. ok.... from the top, sry... so its not a problem that the motors want a little more power and get hot to the touch.... just that my cables are to small and melt? where could i find the electronics to drive these beasts, by the way thanks to all for the help so far. It's not that far yet but i have some pic's of the build. Gonna post them later.
If the motor is overheating, why don't you just machine it a wrap-around heatsink, and use a proper 24v fan (or two) to dissipate the excess energy?
you are incorrect having two PWM systems is not a bad idea aslong as they both have sufficiantly high freqancy. The resistors are a crap ineffeciant way of doing this and 200w of load is going to reduce battry life signifiantly over the 5w or so from PWM (CBA to do the calculations)
two pwm system in series... not just two pwm systems. if their frequencies are similar then you can have troubles of pulses not lining up and causing too much off time etc... I.E. 50% * 50% wont be 25% power. The only way for motor heat to get to the housing of the motor is through radiation and convection, (not that good since air is a bad conductor and not much surface area) and the 2 bearings in the motor. The heat is in the windings, so if the housing is too hot to touch, then the windings are even hotter... A heatsink wouldnt help out a motor that much unless the motor is sealed (no internal fan)
Uhhh.... No? Almost all RC Systems don't come with anything but a transmitter and a reciever (though sometimes you can get kits for aircraft that come with a few servos). Having 2 PWM systems controlling one motor is a moronic idea. If you put them In series, they'll both have to carry the same ammount of current (so there would be no benefits), and you'd get all sorts of intermodulation problems between the two PWM controllers (google beat frequency). If you put them in parallel, they should be able to carry more current, but unless you have some way to synchronise the modulation of the ouput, there would be periods of time when one was on, and one was off, resulting in a (repetative) short duration overload of the controller. In short, either use a bigger controller, or a smaller motor. Period.
Ok, so i have been looking in to the world of pwm and i found this (Victor 885 Speed Controller) 120A continuous should be enough at normal circumstances.The problem is that the only place i can find it is in the US, Europe would be nice. sooooooooo anybody know a place in Europe who sells these? or something similar. much obliged.
Those speed controllers are quite small (The fan on those controllers is a 40 mm), So I can't imagine international shipping being too expensive. Incidentally, Those smaller version of the speed speed controller can handle 60A continuously, and assuming the motors are using 480w, they're only drawing 40A Why do you think you need the bigger version?
because the 24v dewalt motor draws 190Ah at stall current and has a Nominal Amperage of 68Ah, and i cant find any data on the 18v motor. am i overdoing it ?
Ah? What is Ah? Normally Ah stands for amp hours, which is a rating of battery capacity. I really doubt that the motor is drawing 190 amps, let alone 68 A on a continuous basis. The info sheet you have on the motor says 450w. Now, Power = Volts * Amps, so 450 = 18 * I, I = 25 Amps. I can't see any way the motor is foing to draw more than 60 a at 24v. Incidentally, the 60a victor controller is rated for a surge current of 100a for 2 seconds, or 200a for a duration of less than 1 second. Just stick an ammeter on the motor and stall it. That will give you the stall and idle current for sure.
IIRC startup and stall current can/will be 5x higher than running current without a softstart controler, but thats for AC induction motors, i have no idea about dc ones - i would expect it to be similar assuming this is not related to the power factor (something that I never bothered to learn properly at college...)
Nope! While dc motors do have a high stall current, it's for a completely different reason. AC Motors are called induction motors for a reason. They're essentially a giant, rotating transformer. Thus, you have a lot of current draw when they start up because of induction.
Every motor, whether steam, internal combustion, electric or pedal-power uses more energy starting up than when running steady because of 'forceneededtoovercomeinertia'. Newton's 1st Law.
the reason DC motors have a high start up current, is becuase when they start up there is no back emf generated in the motor to lower the effective voltage on the armature, so the start up current is worked out simply with Ohms law I=V/R, so if you measure the armature resistance and divide the voltage of the battery by that you will get the start up and also the stall currents. stall current is the same as start up as there is no movement to generage the back emf.
ok ill be getting two of the (Victor 883 Speed Controller) thanks for helping me. just some images from the project. the body is 1.24 cm long
