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Understanding Speed-Torque Characteristics of Miniature DC Motors (Part 1 of 3)

May 17, 2016

Read: Part II  |  Part III

Portescap offers miniature motor technologies to solve the motion needs of end markets. Our typical markets can range from motors for medical devices to various industrial applications. We serve our customers through innovative product technologies encompassing brushless miniature DC motors, brush DC & can stack motors, disc magnet motors and stepper linear actuators, to optimize their application performance.

A motor is basically a prime mover or a machine, fed with electrical energy as input where mechanical energy is derived at the output. For motoring actions, two fields are required to interact with each other. The two fields which are produced by stator & the rotor are as shown in figure below. We can see the basic parts of stator or magnet, rotor or coil with shaft, along with the housing part, which is a tube and end covers.

Basic Parts of a DC Motor

When electrical power [i.e. voltage & current] is fed as an input to the motor, some form of mechanical power [i.e. torque & speed] is derived as an output. The part of the input energy that is wasted as loss in the stator core and coil, is called as core loss & copper loss respectively. However, since Portescap uses coreless motors, this loss would be extremely negligible.

Speed and torque are important performance parameters of a DC motor. The torque-speed characteristics shown in our catalogue define speed as a function of torque. In most cases, the motor runs at a definite torque and speed in the application, as denoted by Option 1 in diagram shown below. In some cases, the motor may have to run at much higher speed but at lower torque e.g. Option 2. Sometimes, the motor would work in a stalled condition too. Some other applications may demand acceleration of a motor, and this acceleration would need a higher torque at higher speed.  All these are the load operating points & should be considered along with the limits of the motor performance. This understanding will help you to select the right motor for your application.


Various load points in an application powered by a DC Motor


Read: Part II