# 12v dc motor speed self limited?

• moroeder
In summary, the conversation discusses a mechanical engineer's question about a PM brushed DC 12 V fan motor and a PWM 12-24 power source. The engineer is trying to increase the fan's speed to move more air over an air-cooled engine, but is unsure if it will work. The question is posed whether DC motors have self-limiting voltage intake based on their wattage, to which the answer is yes, as the motor's wattage determines the amount of current and voltage it can handle without overheating.

#### moroeder

Fellow Engineering Lovers,

Being a mechanical with limited electrical I must turn to the electron masters for answers. I have a PM brushed DC 12 V fan motor on of a standard electric cooling fan on a car radiator. My calculation comes out to be about 90 watt. I also have PWM 12-24 power source 50 amp that appears to work properly. However the fan in the pushing air direction will only swallow 16.5 volts. In the puller direction 13.5 volts with both at about 10 amps.

I am running the controller on the 24 volt input and with no load I have about 26 volts. The PWM is a very robust piece out of our US military equipment. No heat to speak of and you can certainly tell when the system is turned on because of draw down of the other equipment running in the car. I have an air cooled engine and want to move more air over it by spinning the fan blade faster. Sounds good but don't have any idea if it will work.

Finally my question is, "do these DC motors have self limiting voltage intake based on their wattage?" Sounds crazy but what I am seeing seems like it could be so. Please help a mechanical feel the electrons in a more favorable fashion. And if you can steer me in the right direction that would be good too.

Max

Welcome to Physics Forums moroeder.

moroeder said:
...do these DC motors have self limiting voltage intake based on their wattage?...

Yes, so to speak. The magnet wire used to wind the magnets has resistance which will rise depending on its temperature. So the wattage of the motor tells you how much current and voltage you can supply without overheating it until failure.

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elepow.html" [Broken]

Last edited by a moderator:

## 1. What is a 12v DC motor speed self limited?

A 12v DC motor speed self limited refers to a type of motor that has a built-in mechanism to control and limit its rotational speed. This is usually achieved through the use of a specific control circuit or software.

## 2. How does a 12v DC motor speed self limited work?

12v DC motor speed self limited works by using sensors or feedback mechanisms to monitor the motor's rotational speed and adjust the power supply accordingly. This allows the motor to maintain a constant speed even under varying load conditions.

## 3. What are the advantages of using a 12v DC motor speed self limited?

Some advantages of using a 12v DC motor speed self limited include better control over the motor's speed, improved efficiency, and protection against overloading. It also eliminates the need for external speed control devices and reduces maintenance requirements.

## 4. How do I choose the right 12v DC motor speed self limited for my application?

When choosing a 12v DC motor speed self limited, consider the motor's torque and RPM requirements, as well as the load it will be subjected to. Also, make sure to select a motor with a speed self-limiting feature that best suits your specific application.

## 5. Can I adjust the speed of a 12v DC motor speed self limited?

Yes, the speed of a 12v DC motor speed self limited can be adjusted by changing the input voltage or by using a speed control device, if the motor does not have a built-in speed control feature. However, it is important to note that the motor's self-limiting mechanism will still work to maintain a constant speed within the set limits.

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