Introduction

Selecting a standard BLDC motor is usually the fastest solution for a new product development project.

However, many OEM engineers eventually discover that catalog motors cannot fully satisfy their requirements.

The motor may have:

• Insufficient torque output
• Lower efficiency than expected
• Excessive noise
• High temperature rise
• Large installation size
• Short operating lifetime
• High overall system cost

In these situations, simply changing suppliers rarely solves the problem.

The real solution is developing a BLDC motor based on the actual application requirements.

At Smart Drive, we help OEM engineering teams develop custom BLDC motors from initial concept evaluation to prototype testing and production.

This BLDC Motor Design Guide explains how engineers transform application requirements into a reliable production-ready motor solution.

1. Why Standard BLDC Motors Often Fail in OEM Product Development?

Before starting a custom motor project, we first ask an important question:

Why is the existing motor solution not suitable?

In most cases, customers already have:

• An existing supplier motor
• A competitor product
• A previous generation design
• A standard catalog motor

The purpose of custom design is not simply to create another motor.

It is to solve a specific performance limitation.

Common customer challenges include:

Insufficient Speed or Torque

The existing motor may not achieve the required operating point.

Typical causes include:

• Limited electromagnetic capability
• Incorrect winding design
• Insufficient magnetic flux
• Poor torque-speed matching

The solution may require:

• Optimized winding parameters
• Different pole-slot combination
• Larger magnetic circuit
• Higher efficiency design

Excessive Temperature Rise

A motor may achieve the required output but generate too much heat.

Typical causes:

• High copper loss
• High iron loss
• Poor heat dissipation
• Insufficient motor size

Design improvements may include:

• Lower resistance winding
• Improved magnetic design
• Better thermal path
• Aluminum housing optimization
• Cooling structure improvement

Excessive Noise and Vibration

Noise problems are common in:

• Pumps
• Fans
• Household equipment
• Robotics

Possible causes include:

• Electromagnetic torque ripple
• Rotor imbalance
• Bearing selection
• Poor structural stiffness

Solutions may include:

• Optimized slot-pole combination
• Sinusoidal back EMF design
• Rotor balancing
• Mechanical reinforcement

Large Size or Excessive Weight

For applications such as:

• UAV
• Robotics
• Portable equipment

Motor size directly affects the final product.

Optimization may involve:

• Higher power density design
• Improved magnetic materials
• Structural redesign

High Cost

Sometimes the motor performance is acceptable, but manufacturing cost is too high.

Cost optimization may include:

• Material selection
• Manufacturing process improvement
• Component integration
• Simplified assembly design

A successful custom BLDC motor design should improve both performance and commercial value.

For instance

An automotive cooling pump requires continuous operation at 6000 RPM with a constant torque of 0.5 N·m, and it must sustain stable long-term performance under an ambient temperature of 120°C. In contrast, a standard pump motor is only rated for a speed of 3000 RPM, a torque of 0.8 N·m, and a maximum operating ambient temperature of 60°C.

Due to the significant differences in operating parameters and environmental tolerance between the application requirements and standard motor specifications, targeted customized redesign is mandatory, covering the following core aspects:

• Optimization of motor windings, magnet structures, and slot-pole combinations
• Upgrading of mechanical component materials to enhance high-temperature resistance
• Selection and upgrade of high-temperature-resistant electronic components for motor controllers
• Redesign and optimization of the motor’s internal cooling and heat dissipation structure

2. Step One: Understand Application Requirements

The first stage of BLDC motor development is understanding the application.

We do not start by selecting components.

We start by defining:

Mechanical Requirements

Including:

• Required torque
• Operating speed
• Maximum speed
• Load characteristics
• Duty cycle
• Installation space

Electrical Requirements

Including:

• Voltage
• Current limitation
• Battery or power supply
• Communication interface
• Control requirements

Environmental Requirements

Including:

• Temperature range
• Water resistance
• Dust protection
• Vibration requirements

For example:

A water pump motor may require:

• Continuous operation
• Waterproof structure
• High reliability

A UAV motor may require:

• Lightweight design
• High efficiency
• High power density

Different applications lead to completely different motor solutions.

3. Analyze Existing Products and Define Improvement Direction

Before designing a new motor, we usually analyze the existing solution.

The evaluation includes:

• Motor structure
• Electrical parameters
• Performance curve
• Installation method
• Cost structure

We compare the current motor performance with customer requirements.

The design target becomes clear:

Example:

Existing motor:

• Torque: insufficient by 20%
• Temperature rise: too high
• Noise: unacceptable

Design objective:

• Increase torque output
• Reduce losses
• Improve acoustic performance

This step prevents unnecessary redesign.

4. Select the Correct BLDC Motor Architecture

Inner Rotor or Outer Rotor Design

Inner Rotor Motor

The rotor is located inside the stator.

Advantages:

• Higher speed capability
• Compact structure
• Better mechanical strength

Outer Rotor Motor

The rotor surrounds the stator.

Advantages:

• Higher torque density
• Large diameter magnetic structure
• Good low-speed performance

Integrated Gearbox or Direct Drive

For high torque and low speed applications, a gearbox may be required.

Examples:

• Robotic joints
• Electric actuators

Direct drive is preferred when:

• Low noise is required
• Maintenance must be minimized

Sensor or Sensorless Design

The control method depends on performance requirements.

Sensor-based systems provide:

• Accurate position feedback
• Better startup performance

Sensorless systems provide:

• Lower cost
• Higher reliability

Integrated Controller or External Controller

Modern BLDC systems often integrate:

Power Stage

• MOSFET bridge
• Gate driver
• Current sensing

Control Unit

• MCU
• Communication interface
• Firmware

Protection Circuit

• Over current protection
• Over voltage protection
• Over temperature protection

Thermal Design

Controller heat is usually transferred through:

• Aluminum housing
• Heat sink
• Thermal pad
• Potting material

Applications:

• Automotive pump
• UAV actuator
• Robotics

How Engineers Select the Right BLDC Motor Architecture?

For example：

UAV Application

Requirement:

• High power density
• Lightweight
• Direct drive

Preferred:

Outer rotor BLDC motor

Pump Application

Requirement:

• High speed
• Compact size
• Waterproof

Preferred:

Inner rotor motor

Requirement:

• High torque
• Precise positioning
• High dynamic‑response capability

Preferred:

Inner rotor + gearbox + encoder

5. Preliminary Motor Concept Design

After defining the architecture, we create the first motor concept model.

The preliminary design includes:

• Motor outline dimensions
• Mounting structure
• Shaft interface
• Electrical connector
• Communication interface
• Cooling method

At this stage, we confirm:

• Installation space
• Mechanical interface
• System integration requirements

The preliminary model allows customers to verify:

• Product compatibility
• Assembly method
• Size limitations

6. Electromagnetic Simulation and Optimization

During the BLDC Motor Design Guide process, electromagnetic optimization is one of the most important engineering stages.

We perform simulation analysis to optimize:

Stator Design

Including:

• Slot number
• Lamination size
• Winding arrangement
• Wire specification

Rotor Design

Including:

• Magnet grade
• Magnet thickness
• Pole configuration
• Magnetic circuit

Performance Analysis

Simulation results normally include:

• Rated torque
• Peak torque
• Back EMF waveform
• Cogging torque
• Torque ripple
• Efficiency map

Thermal simulation evaluates:

• Copper loss
• Iron loss
• Temperature rise

The design is repeatedly optimized until performance targets are achieved.

7. Detailed Mechanical Design

After electromagnetic optimization, After electromagnetic optimization, we finalize the mechanical layout of the BLDC Motor Structure.

The detailed design includes:

Rotor Assembly

Including:

• Shaft
• Rotor core
• Magnets
• Balance structure

Stator Assembly

Including:

• Core
• Insulation structure
• Windings
• Terminal connection

Housing Structure

Including:

• Bearing installation
• Fastening method
• Heat dissipation

Special Designs

Depending on application:

• Waterproof sealing
• Cooling structure
• Gear mechanism
• Integrated actuator
• Controller mounting

All components must satisfy:

• Assembly requirements
• Manufacturing tolerance
• Reliability requirements

8. Engineering Drawings and Prototype Manufacturing

After completing 3D design, we generate production drawings.

Engineering drawings define:

• Material requirements
• Dimensions
• Tolerances
• Surface treatment
• Assembly requirements

Prototype validation is a critical stage in the BLDC Motor Design Guide because simulation results must be verified through physical testing of the Custom BLDC Motor Prototype.

Prototype manufacturing includes:

• Machined parts
• Molded components
• Winding process
• Motor assembly

9. Prototype Testing and Optimization

Prototype testing validates the design.

Typical tests include:

Performance Testing

• Speed
• Torque
• Efficiency
• Power output

Thermal Testing

• Temperature rise
• Continuous operation

Reliability Testing

• Noise
• Vibration
• Lifetime evaluation

If testing results do not meet requirements, we return to the design stage.

The development process is iterative:

Design →

Prototype →

Test →

Optimization →

Validation

10. Transition to Production

After prototype approval, the motor enters production preparation.

We optimize:

• Manufacturing process
• Assembly fixtures
• Quality control
• Supply chain

Smart Drive supports:

• Prototype production
• Low-volume manufacturing
• OEM production

BLDC Motor Design Process: Engineering Deliverables by Smart Drive

At Smart Drive, we offer end-to-end custom BLDC motor development services, paired with a professional BLDC Motor Design Guide to streamline and support your entire motor development process.

Stage 1 Requirement Definition

Output:

• Motor specification sheet
• Performance target
• Installation requirement

↓

Stage 2 Concept Design

Output:

• Motor architecture
• Preliminary 3D model
• Electrical interface

↓

Stage 3 Electromagnetic Design

Output:

• Motor electromagnetic model
• Simulation report
• Performance curves

↓

Stage 4 Mechanical Design

Output:

• 3D CAD model
• 2D manufacturing drawings
• BOM

↓

Stage 5 Prototype

Output:

• Prototype samples
• Test report

↓

Stage 6 Production

Output:

• Process documents
• Quality standards

Conclusion

A successful BLDC motor is not created by selecting components randomly.

It requires a structured engineering process:

Application analysis →

Architecture selection →

Electromagnetic optimization →

Mechanical design →

Prototype testing →

Production validation

Through a complete BLDC Motor Design Process, OEM companies can achieve higher performance, better reliability, and faster product development.

1. How long does a custom BLDC motor design take?

Typical development:

0.5-2 months depending on complexity.

2. Can you modify an existing BLDC motor design?

Yes.

Common modifications include:

• Torque increase
• Speed adjustment
• Size reduction
• Thermal improvement

3. When should OEM companies choose custom BLDC motor design?

When standard motors cannot meet:

• Performance
• Size
• Cost
• Reliability requirements