DC Motor Speed Increases Under Load - Modeling w/ Simulink

Click For Summary
SUMMARY

The discussion centers on modeling a simple brushed DC motor using Simulink. Under no-load conditions, the motor achieves a maximum speed of 180 rads/s, while under load, it unexpectedly reaches 290 rads/s, albeit with a longer time to reach this speed and decreased acceleration. Key principles highlighted include the relationship between torque and current, and how back EMF is proportional to RPM. The user is advised to review their model to align with these electrical and mechanical principles.

PREREQUISITES
  • Understanding of DC motor principles, including torque and current relationships.
  • Familiarity with back EMF concepts in electric motors.
  • Basic knowledge of Simulink for modeling dynamic systems.
  • Awareness of mechanical load effects on motor performance.
NEXT STEPS
  • Review Simulink modeling techniques for DC motors.
  • Study the impact of load on DC motor speed and torque characteristics.
  • Learn about back EMF calculations in electric motors.
  • Explore advanced modeling techniques for dynamic systems in Simulink.
USEFUL FOR

Electrical engineers, mechanical engineers, and students interested in motor dynamics and simulation modeling, particularly those using Simulink for system analysis.

Nick Goodson
Messages
7
Reaction score
2
Hi, I am modelling a DC motor using Simulink.
Under no-load conditions, I get a max speed of 180 rads/s, but under load, the speed goes up to 290 rad/s, although takes longer to reach max speed, acceleration decreases.
I have a mechanical background so don't know much about motors, but would expect that, under load, the speed would reduce?
Any ideas?
Many thanks.
 
Engineering news on Phys.org
Assuming it is a simple DC motor with brushes.
Torque is proportional to current. Back EMF is proportional to RPM.
Applied voltage – back EMF appears across the rotor resistance and so decides current.
Unloaded speed will be proportional to applied voltage.
Increasing load will slow the motor until current rises to give torque required.

You have a problem with your model.
 
  • Like
Likes   Reactions: jim hardy and cnh1995
Ok, thanks Baluncore. I need to review what's happening.

Cheers
Nick
 

Similar threads

Electric motor - variable torque vs speed
  • · Replies 13 ·
Replies
13
Views
2K
Loading / Rapid de-loading of DC motor
  • · Replies 74 ·
3
Replies
74
Views
6K
Adding a known load to a DC motor
  • · Replies 9 ·
Replies
9
Views
3K
How to Calculate Angular Acceleration of Miniature Car Tires Using DC Motor?
  • · Replies 2 ·
Replies
2
Views
2K
Why Did My DC Motor Fail Under Load?
  • · Replies 8 ·
Replies
8
Views
3K
Why does a DC series motor not reach a steady speed?
  • · Replies 7 ·
Replies
7
Views
3K
Cheapest Way To Reverse/Vary Speed of DC Motor
  • · Replies 18 ·
Replies
18
Views
5K
How Do Inductors and Back EMF Influence DC Motor Behavior?
  • · Replies 1 ·
Replies
1
Views
2K
Superconducting motor thought experiment/ questions
  • · Replies 1 ·
Replies
1
Views
2K
PI control of a PMDC motor at low speeds
  • · Replies 7 ·
Replies
7
Views
1K