Wipermotors - overvoltage, increasing speed

Hi guys!!

I brought 5 wipermotors couple days ago... (15US dollars for all, so its not big money if I burn them )
All of them are 12 volts. Torque is huge.. I havent datasheets, but me and my friend cant make them stop
So I think that can sacrifice the torque...

I am not very familar with dc motors... so im asking your for your advice!

I power them with this device http://www.gsm-technology.com/index.php ... ories.html
(one per motor)
So I can easily reduce the current with this power supply!

My aim is increase the speed by increasing the voltage to 24 volts, maybe 20!
In my experiments, if I run the motor with 12v and 5A, my power supply shows me 0.7A without load and 2.0-2.3A with max load...
I also tried to run motor with 24 volts without load for 3-5 mins and the temperature of the motor didn't grow..
If I load(quickly change direction) the motor current growing(in peak) to 3-3.5 Amps...

Correct me if I'm wrong... If I limit the current, for example, to 2.5-3 Amps.. and increase the voltage to 24 volts the motor will be more or less in safe?

You have to understand the concept of voltage and current. By limiting the current, you are also limiting the voltage. Current(electron flow) is the result of voltage (electrical pressure). If you have more voltage, you will push more current through the same resistance. Ohm's Law: I = V/R. Pretty much the same principle applies to torque, load, and speed also. Speed = Torque / Load. You have more torque, you have more speed, if you want to increase speed, increase torque or decrease load.

If you limit your current, all you are doing is telling the power supply to lower the voltage if the current exceeds your limit. Lowering the voltage lowers the current.

Also, you have to understand that your motor is not controlled by voltage, but current. More voltage will give you more current, and that is why you will get more power. Limiting your current on the motor is just going to limit your torque (therefore the speed also).

There is a lot of theory behind motor dynamics, inductive loads, how current flows and gets distributed. I'm not going to get into it, you can search google for more info.

To save your motors, you should just watch for tempreatures. If the motor doesn't heat up significantly, you are safe. If it does, put heatsinks on it to prolong it's life.

Frakk thank for your response!

I am reading more articles about DC motor to dig into theory!
I have couple question...
One about temperature. I understand that different motors designed for different temperature, but maybe there are general maximum temperatures? 100 degrees? 60 degrees?

I looked through all forum.. but nobody asked why wiper motor have THREE brushes(instead of two)...
maybe i am the only person who don't know how works third brush
I google it, it says that third(shifted) brush is for second speed (faster)... I tried differend connection(brushes), but I see the same speed! May be I do something wrong or don't understand something!!
How should I correctly connect my motor to get highest speed?
Here is link http://www.sw-em.com/Windshield%20Wiper%20Systems.htm

The motor that they disassembled have two brushes, but circuit in the end of the page have three, like my motors.
If there is need, I can attach photo of my disassembled motor in the evening, to show brushes!

That seems to be a good article about these motors. I will read it when I have time later today.

The third brush has to be an extra contact to increase the speed in one direction, but don't quote me on that. I'll post more after reading through that page.

You use the two brushes that are opposite to each other to get the same speed in both directions. The offset brush is for the high speed and can only be connected when the other brush on the same side is disconnected. The high speed only works in one direction only.

Senetor.

yes...((( its true...

http://www.youtube.com/watch?v=lC8oCxqM ... re=related