torque and speed for dc motor?

Question

Hi,

I know that for a typical dc permanant magnet motor, there is a quadratic relationship between the power and torque,the same goes for power and speed. The max power occur at 1/2 the stall torque,this is also true at 1/2 the no load speed.

Can someone please tell me what is the difference between a constant torque and a constant speed motor? While choosing the right motor for an application(in my case a motor powered screw jack), I only look at the motor's power rating,voltage,max current,stall load and no load speed, i did not see in catalogs for dc motor, whether it is a constant torque or a constant speed motor.

Thank you.

Answer 1

One uses a speed controller to control the speed required for a piece of equipment when one uses a DC motor. The DC motor torque is the torque required to overcome the magnetic torque of the motor to start rotation.

Answer 2

Speed is a measure of how far something travels in a given period of time. The rate of change in position. For a motor, speed is measured in revolutions per minute.

Torque is force exerted as an object rotates. To turn a motor shaft requires a certain amount of torque. If a load is added to the shaft, more torque is required to turn it.

Two motors of different sizes may run at the same speed. A shaded-pole motor (example: window fan) exerts very little torque. A common speed is 1800 or 1200 RPM.

A large industrial motor (example; factory conveyor belt) may exert a very high torque in order to start a heavy load, and yet it runs at a similar speed.

The same is true of engines. An eight cylinder car engine can run at 3600 RPM and exert a great amount of torque. A small generator will run at 3600 RPM, but not exert nearly as much torque as the car.

https://www.electrikals.com/

Answer 3

[1] Reverse DC power polarity. [2] Vary the supply voltage. [3] Same as [2]. [4] No such function for motor. [5] Apply power to motor brake.