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DC Motor / Gearmotor Selection

Updated: Jan 20, 2023

What is a DC Motor?

A direct current (DC) motor is a revolving electrical apparatus that transforms electrical energy from direct current into mechanical energy. When DC voltage is provided to the terminal of an inductor (coil) within a DC motor, the magnetic field it generates causes the motor to rotate.

A gear motor combines a motor and gearbox into one unit. When a gear head is added to a motor, the speed is decreased but the production of torque is increased. In terms of gear motors, speed (rpm), torque (N-m), and efficiency (%) are the most crucial variables. You must first determine the load, speed, and torque required for your application in order to select the ideal gear motor.

The Motor Selection Process

Design Requirements – A design assessment phase where the product development requirements, design parameters, device functionality, and product optimization are studied.

Design Calculations – To figure out which motor would be the optimum fit for your application, calculations are employed. Gear ratio, torque, rotational mass, service factor, overhung load, and testing analysis are all determined by design calculations.

Types of DC Motors/Gearmotors – The most common electrical motors that convert electrical energy to mechanical energy. These types of motors are powered by direct current (DC).

Motor Specifications – You can use this information to identify which motor or gear motor will work best for your application once the design calculations have been completed and the application parameters have been established. Some of the most common specs to consider when selecting a motor or gear motor would be:

  • Voltage

  • Current

  • Power

  • Torque

  • RPM

  • Life Expectancy / Duty Cycle

  • Rotation (CW or CCW)

  • Shaft Diameter and Length

  • Enclosure Restrictions

Water and Dust Protection - A DC motor's ability to resist water and dust is also sometimes indicated by its IP (Ingress Protection) rating. The IP rating is essentially explained in the graphic below.

Tips For Selecting a DC Motor or Gear Motor For Any Application

When it comes to the motor-choosing procedure, there are a few aspects to take into account. Electric motors are known for converting electrical energy into mechanical energy, but there are many different models available today. With our 4 Motor Selection Tips, we hope to help you focus and go on the correct path during the difficult process of choosing a motor.

1. Determine STV

Voltage, speed, and torque are the three key parameters that you must understand for every application involving a DC motor. You are now prepared to begin your search for the appropriate motor option once these factors have been established. Utilizing a motor that is close to or at full efficiency is crucial.

When choosing a motor, it's important to establish the motor voltage as well. Your electrical power sources, such as a 12-Volt battery or power supply, will decide the motor voltage. DC motors typically have a nominal voltage of 12 or 24 VDC.

Any application involving motion control needs to consider rotational speed. How quickly a DC motor will run when a load is applied is known as the rated or on-load motor speed. It's crucial to understand the motor's required constant and maximum speeds.

The amount of load that a motor's output shaft can handle at a specific position is known as motor torque. A motor's torque and speed are inversely correlated; when one goes up, the other goes down. Just like the speed, the rated torque, also known as on-load torque, needs to be defined. The motor's stall torque or peak torque is a crucial component of torque.

By examining a motor's performance curve, which is frequently included with the motor specification, it is possible to understand the relationship between torque and speed the best.

In order to select an effective motor for your application, it is essential to select a motor or gear motor that satisfies your speed and torque needs.

2. Balance Size vs. Performance

For every application, choosing the right motor size is crucial, but if specific performance is needed, it may become problematic. Generally speaking, bigger motors have greater power than their little brothers. You might have to make some performance concessions, depending on the demands of your application, to help meet the size restrictions.

There are several ways to help meet the size restrictions for the majority of applications by utilizing various motor types and motor technology, such as brushless motors or motors with permanent magnets.

3. Gear Motors Offer More Torque

There are instances when you require greater torque than a typical DC motor can produce. The torque and speed produced by a DC gear motor depend on the selected gear ratio, which also affects the speed. Spur gear motors, planetary gear motors, and worm gear motors are the three most common types of gear motors. Each variety of gearhead has unique advantages.

Stepper motors, brushless DC motors, and brushed DC motors can all be equipped with gearheads. Check read our design note to learn more about the distinct characteristics of the various gear motor types. Spur motors vs. planetary gear motors.

4. Define The Duty Cycle

Which motor type is ideal for your application or gadget will depend on your duty cycle. Key components of your duty cycle are directional rotation, operating times, and dwell times. The motor selection process should begin with the definition of the duty cycle.

For the majority of industrial applications, intermittent duty cycles are recommended to assist a motor or gear motor last longer. Continuous use is still permissible as long as the motor is performing at its highest level of efficiency.


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