What is a DC Brush Motor

A brushed DC motor is a motor that uses brushes and a commutator to convert electrical energy into mechanical energy. Because of the mature design of DC brush motors, low cost, and high cost performance, they are widely used in the field of micro drive industry.

In this article, we will share the basic knowledge of DC motors ( What is a DC motor and How to choose a suitable DC motor )

Working Principle of DC Brushed Motor

1. Basic Components

A DC brushed motor consists of three main assemblies:

• Housing : Iron shell and permanent magnets.
• Rotor : Commutator, enameled wire windings, and laminated silicon steel core.
• End Cap : Rear end cap, brush holder, and carbon brushes.

2. Role of Magnets

According to Faraday’s Law of Electromagnetic Induction, when a conductor cuts through a magnetic field, it generates Ampere force, which drives the rotor’s rotation. The magnetic field strength directly impacts motor power output.

Common Magnet Types:

• Ferrite Magnets (Low cost, weaker magnetic field ~3.5 MGOe)
• Neodymium (NdFeB) Magnets (High magnetic strength up to 50 MGOe, but 5-8x more expensive)

Magnet Selection Principle:

• Low-power applications (e.g., toys) → Ferrite magnets
• High-power applications (e.g., power tools) → Neodymium magnets

3. Commutator and Brushes

The commutator is a split ring attached to the rotor shaft, while the carbon brushes are stationary contacts. Together, they enable current transfer to the rotor windings.

How to Calculate the Power of DC Motor

To determine the power of a DC brushed motor, we need to analyze three key aspects: input power, power loss, and output power.

1. Input Power

The total electrical power supplied to the motor is given by: $$P_{\text{input}} = U \times I$$

Where:

• U = Input voltage (V)
• I = Circuit current (A)

2. Power Loss

Some energy is lost due to electrical resistance, primarily in the form of heat. The power loss can be estimated using Joule’s law: $$P_{\text{loss}} = I^2 \times R$$

Where:

• R = Internal resistance of the motor (Ω)

3. Output Power

The useful power output of the motor is its mechanical power, which is calculated as: $$P_{\text{output}} = E \times I$$

Where:

• E = Electromotive force (EMF) of the circuit
• E can be expressed as:

$$E = K N \Phi$$

Where:

• K = Motor constant
• N = Motor speed (RPM)
• Φ = Magnetic flux

Thus, the final formula for output power becomes: $$P_{\text{output}} = K N \Phi I$$

Conclusion

By balancing input power, power loss, and output power, we can evaluate the efficiency and performance of a DC brushed motor. Optimizing motor parameters such as voltage, current, resistance, and magnetic flux helps achieve better efficiency and output performance.

How to Choose dc motor ( 10W examples )

Selecting the right size motor for your application requires specialized knowledge. Take a rated input voltage of 24V and a rated output power of 10 W as an example.

Although the three motors have the same rated power, they have different sizes and different rpm.

The small-sized DC 395 motor needs a rated speed of 9000 to output 10W of power. The large-volume DC 775 motor only needs a rated speed of 3000 to achieve the same power.

Rpm = Less lifetime / more noise

So we need to choose the appropriate size motor according to the requirements of the application space.

How to Test DC Brush Motor

We utilize specialized DC motor dynamometer equipment for precise performance testing. The motor is mounted on a custom fixture and initially runs without load. The dynamometer then gradually increases the load torque at the motor’s shaft end while recording current, speed, and power under varying load conditions. This process generates a comprehensive motor dynamometer report for performance analysis.

Noise Test of DC Brush Motor

The noise test standard of the DC motor is in a quiet room, at a distance of 30cm, and the data tested by the decibel meter is the standard noise data.

Watch Our Video for more specific information

Youtube Link : Doncen Motor