Electric Slides Motor

wa8yxm wrote:

ScottG wrote:


Per the OP's first post, he has a travel trailer so there are none of the interlocks customary to a MH. Further, it has simple rack and pinion type slides so no controller.

Lastly, I'm sorry but some of your assumptions about DC motor current are not accurate.
IE, "lowering the voltage raises the amp draw of a motor". V=I*R. The "R" or resistance of the motor is set. The watts of the motor (P=I*V) is determined by the voltage and amps. It will only deliver the specified watts if the voltage and amps are the ones specified. So if you say a motor has 100 watts for example.....you can't say if I connect half the voltage to it, it will automatically double the amps. Doesn't work like that. The actual voltage and amps given to the motor determined by the RESISTANCE of the motor will determin your power (P=I*V) or ((V^2/R)=P) or (I^2*R=P) The first of the formulas are first and formost determinded by V=I*R. It rules it....it owns it. The other two formulas above have R in them.....these you can use. Take the second one ((V^2/R)=P) for example. We just went from 12 volts to 8 volts. Lets say for the sake of the argument.....the ohms (resistance) of your motor is 1 ohm. (12^2)/1=144 watts. Lower it to 8 volts.... (8^2)/1= 64 watts.

Source https://www.physicsforums.com/threads/current-draw-of-a-motor-under-different-situations.585336/

Cheers,
Scott

Well then disregard the interlock info. There IS a controller for the Rack and Pinion Slide. It may be hard to find (I had to use an electronic bloodhound) but there IS a controller of some kind the full motor current would melt the switch in the wall.

That the motor used by Power Gear increases current as speed drops is a proven fact..

Having visited you link I understand your confusion however. But I also studied motors and there are multiple types of motors.

For example one motor tries to run at a constant speed if you slow it down it will Draw more WATTS (normally this means more current) but try to maintain speed.

Another type of motor.. Well this one is used in electric lawn moweres and Black and Decker in the owner's manual yammered about a "Sensor" the increased motor power to handle taller grass.. Kind of made me laugh (Series wound motor) As the motor slows it REALLY draws more current (more watts too) so as to keep turning...

My little electric marched through knee high grass on a neighbor's yard his gas powered unit would not even touch..

I once worked in a feed mill.. The grinder no load full voltage abou 50 amps.. Feed it corn and it would easily hit 300-400 amps as the load increased and the mill slowed a bit.. I even have been trained as to why but alas. Have not refreshed that memory in many years.

As a retired EE from the aviation industry, I can assure you that *I* am not confused. It is you that is confusing AC and DC motors - 2 very different animals. The motors you wrote of have no bearing on this application.
The OP's slide has very simple DC motors. It has no circuit to increase power when needed and most of all, it does not draw more current when the voltage is low.