A Complete Guide On Selecting A DC Motor

DC motors are electric motors that you can power by direct current (DC), from a DC power supply or battery. The commutation of DC motors is brushless or brushed. You can control the speed of the brushed motor by changing the voltage alone. You can power an AC motor by alternating current (AC), defined by frequency and voltage.

So, motors powered by AC need a change in frequency to alter the speed. It involves more complex and expensive speed control, so, it makes DC motors well suited for equipment ranging from 12VDC systems in automobiles to conveyor motors. Both of these require fine speed control for a range of speeds above and below the rated speeds.

When one is selecting DC motors, industrial buyers need to identify and see:

• The key performance specifications
• Determine design
• Size requirements
• Consider the environmental requirements of their application.

If you are searching for the right China DC motor, here is a complete guide to assist you in selecting the right one that best matches your task requirements.

Specifications Of Performance:

The most vital performance parameters for DC motors are:

• Torque
• Speed
• Operating Voltage

Requirements Of Application:

Buyers must compare the list on a DC motor’s datasheet to their application requirements. As the output of motor parameters are dependent, some specifications depend on the following selections:

Shaft speed:

To rotate a shaft at a proportional rotational speed, a DC motor applies a voltage. Shaft speed specs refer to the no-load speed. This is the maximum speed reached by the motor when no torque is applied. Shaft speed is set in rotations or revolutions per minute. You can relate these rotations or revolutions to several radians to express the motor speed in radians per second.

Output torque:

In a motor, shaft rotation produces torque, which is a rotating force and, this is the maximum load that the motor can produce or handle. You can measure the torque in units of force-distance. The stall torque and continuous torque are the two most used torque specifications. The torque at which the shaft speed is zero or the motor stalls is known as stall torque.

At normal running conditions, continuous torque is the maximum. The torque of a DC motor is proportional to the armature current, and the torque constant is the constant of proportionality.

Available Voltage:

If a small or a specific power supply is available, you can use DC motors to run at a specific voltage. You can also determine the rated speed of the motor by the stated voltage. You can see voltage in volts.

Derived Specifications:

Parameters generated from or linked to the essential requirements are also included in DC motor datasheets.

Output Power:

The product of the motor’s rated torque and speed is the rated output power. At 50% of the no-load speed and the stall torque, you can reach the maximum output power. Many manufacturers state the output power in horsepower. To convert a calculated value of power, from watts to hp, multiply the watts by 746.

Power dissipation:

In a DC motor, the current produced dissipates power and warms the motor. The resistance of the entire motor system, including friction losses in the stator and rotor, is connected to total power dissipation.

The current of the motor allows us to determine the power dissipation. As a result, the rotor temperature increase due to spinning. Calculate the total motor temperature by adding the rotor temperature to the ambient temperature.

Types of DC Motors:

There are different types of DC motors available in the market, and every motor has its benefits based upon the construction of the motor.

Shunt Wound:

Shunt-wound motors have minimal speed variation across the load range and can set for consistent horsepower over a variable speed range. You can use these in situations that need precise speed and torque control.

Series Wound:

For permanently attached loads, series wound motors have large starting torques and are essential to avoid damage from high-speed circumstances. These motors produce a lot of torque and can run at low speeds. They are suitable for heavy-duty industrial applications where heavier loads must move slowly and lighter loads must move fast.

Compound Wound:

For constant-speed applications requiring higher torque, compound wound motors are constructed with both series and shunt winding. As a result, you can use these in situations when the major load need is a high starting torque and changeable speed isn’t needed. The examples of this application include:

• Elevators
• Hoists
• Industrial shop equipment

Permanent magnet:

You can integrate a magnet permanently with the assembly of motors, and there is no winding field. They provide good starting torque and provide steady speed with varying loads. Permanent magnet construction is more efficient than winding magnet construction, although it has less speed regulation.

Disc Armature:

Flat rotors are powered by an axially aligned magnetic field in disc armature motors, also known as “pancake” or “printed armature”. With their lightweight, they have a low moment of inertia, allowing them to accelerate quickly. These motors are ideal for applications that require fast startup and shutdown while carrying a steady load, such as an electric vehicle.

Coreless And Slotless:

Motors with a cylindrical winding that is physically outside of a set of permanent magnets are known as coreless and slotless. These designs have lower inertia since the winding is laminated and there is no iron cage. They have great acceleration, efficiency, speed control, and low to no vibration. You can also use them in the process control applications as servomotors.

When you have determined the type of motor you need, you must contact Electric DC motor manufacturers and get the product to accomplish your tasks.

Considerations Of Size and Environment:

Sizing Considerations:

Shaft configuration:

It determines how the motor is mounted and connected to the device it powers. The selection of shaft is important for the compatibility of the system. Best selection improves the effectiveness and saves time and cost during assembly. Configurations may include:

• Concave
• Round
• Square
• Hexagonal
• Splined
• Grooved
• Stepped
• Screw types

Gearing:

You can use this in the motors to increase or reduce shaft speed. It inclines to decrease the volume or weight of the motor. The gear types used in DC motors include:

• Spur
• Planetary
• Harmonic
• Worm
• Bevel gears.

Environmental Considerations:

Operating temperature:

You can consider this when using sensitive electronic equipment. This happens when the environment is not at the standard of 40°C, or when the environment is sensitive to a motor’s heat dissipation. You can install additive cooling mechanisms to counter excessive heating of the motor or the surrounding environment.

Corrosion protection:

You can consider this in environments where the motor is exposed to:

• Radiation
• Dust
• Hazardous substances

These can degrade the motor. Select the proper motor enclosure and materials to ensure protection against pollution.

Water protection:

You must consider this when a motor can operate while exposed to water. The levels of protection range from protection against minimal vertical dripping to full submersion under pressure.