Project Proposal
Separately Excited DC Motor for Enhanced Torque and Speed Control
1. Project Title
Design and Implementation of a Separately Excited DC Motor for Precise Speed and Torque
Regulation
2. Abstract
Permanent magnet DC motors are widely used for their simplicity, but they offer limited
control due to their fixed magnetic fields. This project proposes the design and
implementation of a separately excited DC motor, where the magnetic field is generated by
an independent electromagnet. This allows real-time control of field strength, enabling
precise modulation of speed and torque. A custom PWM-based control system will be
developed and implemented using a microcontroller. Performance will be compared to
conventional permanent magnet DC (PMDC) motors to evaluate improvements in efficiency
and flexibility. As a future enhancement, the team also plans to integrate wireless control
through a mobile app, enabling remote speed and torque management.
3. Objectives
- Design and build a DC motor with independent field excitation.
- Develop a dual power system for armature and field circuits.
- Implement PWM-based control of the field current for real-time modulation.
- Measure and analyze motor performance in terms of speed, torque, and efficiency.
- Compare results with a traditional PMDC motor to highlight improvements.
- Document all findings in a detailed report with experimental data and analysis.
- Future Objective: Integrate mobile app control for wireless motor management.
4. Background and Motivation
While PMDC motors are common in small-scale applications, they lack flexibility in speed
and torque control due to the fixed field strength. In contrast, separately excited DC motors
(SEDC) allow independent variation of armature voltage and field current, enabling
dynamic control over motor behavior. This is especially useful in applications such as
electric vehicles, CNC machines, and robotics where performance tuning is crucial. This
project is motivated by the need for greater control in torque and speed modulation, a
programmable system adaptable to varying load conditions, and an entry point into more
advanced intelligent motor control systems, including IoT and mobile interfaces.
5. Scope of Work
- Mechanical and electrical design of the SEDC motor
- Construction of the field and armature winding system
- Power electronics for independent dual-channel control
- PWM control system using microcontroller
- Measurement of RPM, torque, voltage, current, and temperature
- Comparative testing with a PMDC motor
- Mobile app planning for future wireless control
6. Theoretical Foundation
DC Motor Working Principle:
In a separately excited DC motor, the magnetic field is supplied by a separate DC source,
providing independent control over the magnetic flux (Φ) and armature current (Ia).
Torque (T) and speed (N) are governed by:
T ∝ Φ × Ia and N ∝ (V - Ia × Ra) / Φ
Adjusting the field current enables dynamic control over torque and speed.
PWM Field Control:
PWM (Pulse Width Modulation) allows precise control of average voltage across the field
coil. Varying the duty cycle changes magnetic flux density, which directly affects torque and
speed.
7. Methodology
Design and Simulation:
- CAD modeling of motor structure
- FEMM or ANSYS simulation of magnetic field patterns
Fabrication:
- Winding of armature and field coils
- Motor body and shaft construction
- Assembly of rotor-stator and brush system
Control System Development:
- Dual power system setup
- PWM-based control using microcontroller
- Sensor interfacing for RPM and torque monitoring
Testing and Analysis:
- Vary field current to observe performance response
- Record data for different load conditions
- Compare with PMDC motor under identical conditions
Future Plan:
- Mobile App Control: Use Bluetooth or Wi-Fi module for wireless motor control
- App features: speed setting, real-time monitoring, start/stop control
8. Project Timeline (10 Weeks)
Week 1: Literature review on SEDC motors and control techniques
Week 2: Design mechanical layout and simulate magnetic flux
Week 3: Material procurement and coil specification finalization
Week 4: Motor assembly and coil winding
Week 5: Power circuit design and simulation
Week 6: Assemble control system and implement PWM logic
Week 7: Test motor performance under variable field conditions
Week 8: Perform comparison with PMDC motor
Week 9: Optimize design and document results
Week 10: Report writing, presentation, and future development outline
9. Expected Outcomes
- Operational prototype of a separately excited DC motor
- PWM-based control system for field modulation
- Performance graphs showing torque-speed relationships
- Technical comparison with PMDC motor
- Concept design and outline for mobile app integration
10. Team Roles
- Mechanical Lead: Motor body, rotor alignment, fabrication
- Electrical Lead: Coil design, circuit implementation
- Control Systems Lead: PWM and microcontroller integration
- Documentation Lead: Report, logs, presentation
- (Future Role) App Development Lead: Mobile app interface and communication setup
11. Tools and Components
- Enamel copper wire for armature and field windings
- Soft iron core and rotor laminations
- Dual-channel power supply (12V–24V)
- MOSFETs/IGBTs for switching
- Microcontroller (Arduino/STM32)
- Bluetooth/Wi-Fi module (for future app control)
- Oscilloscope, tachometer, torque sensor
- CAD, FEMM/ANSYS for simulation
12. Risk Analysis
Risk: Coil overheating | Mitigation: Use appropriate gauge wire and PWM control
Risk: Rotor imbalance | Mitigation: Perform pre-installation balancing
Risk: Electrical instability | Mitigation: Use regulated power supplies and filters
Risk: App communication delay (future) | Mitigation: Use efficient low-latency
communication protocol
Risk: Brush wear | Mitigation: Choose durable brushes and spring tension adjustment
13. Conclusion
This project explores the design and implementation of a flexible and controllable DC motor
system using a separately excited configuration. Through theoretical study, practical
prototyping, and comparative testing, the project demonstrates enhanced control of motor
performance. The integration of a PWM control system lays the foundation for intelligent
motor applications. In future iterations, wireless control via a mobile app will further
extend the usability of the system, making it suitable for modern automation, IoT, and
remote robotics applications.
