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This eBook with 84 pages shows the basics of BLDC Motors (brush less direct current). The focus of this eBook are DC-Motors that are driven an DC-Voltage with the help of frequency converter. AC-Motors are not in scope of this eBook but we will show how to operate a AC-Motor on DC-Supply with a frequency converter.
In the first chapter we describe the basics of rotary motion of electrical motors like magnetic field, force, current, voltage and so on. The difference between DC- and AC-motors will be described.

In the second chapter the classical DC-motors with brushes will be detailed analysed. With animations the principal functionality will be shown.

In the third chapter the first motor without brushes the stepper motor will be discussed. With the basics of the stepper motor the really BLDC-motor (Brush Less Direct Current) will be detailed described in the chapter four.

In the last two chapters 5 and 6 the different algorithms for the control of the BLDC-motor like sine-control, sensorless-control and also complex algorithms like FOC (Field Oriented Control) will be explained. With a lot of animation we try to help you the understanding of this complex algorithms. No more mathematical explanation as necessary.




  • Energy consumer
  • The electric motor
  • Power, speed, torque and efficiency
  • Basic function of a electric motor
  • Coil, magnetic field, current and mechanical force
  • AC generator and AC motor
  • Synchronous and Asynchronous
  • Frequency converter
  • Types of electrical motors

 DC motor with brushes

  • Wire loop is rotating
  • Change the direction of the DC current
  • Brushes respectively collector
  • Change the rotation direction
  • Transistors as switches
  • How much is the idle speed?
  • Torque-Speed characteristic
  • Linear motor
  • Dimensioning a system

 Stepper motor

  • Introduction
  • Types of rotors
  • Hybrid stepper motor
  • Angle per step
  • Types of stator
  • Control of unipolar and bipolar
  • Only one coil in operation
  • Full step operation
  • Half step operation
  • Vector control
  • Micro step method
  • Voltage or current control
  • Current control
  • Stepper motor driver
  • Data sheet of a stepper motor
  • Dimension s system

 Brushless motor (BLDC)

  • Introduction
  • Replace rotor and stator
  • Simple rotating magnetic field
  • The rotor do not rotate synchron
  • Sensors for position recognition
  • Hall sensor
  • Mechanical and electrical revolution
  • Mechanical and electrical revolution
  • One, two or three sensors?
  • Wye- or delta connection?
  • Torque and the number of pole pairs
  • How to drive three coils with a DC voltage
  • Electronic switchers
  • Closed loop
  • Left-Right and starting procedure
  • How to change rotation speed
  • Change the speed with PWM
  • Closed loop control
  • Different names for BLDC
  • Inside or outside rotating machine

 BLDC algorithms

  • Sine control
  • Trapezoidal and sine commutation
  • Sine voltage with PWM signal
  • Sine signal in software
  • Lead and lag angle delay
  • BLDC without sensors
  • Induced voltage in the coil
  • Zero crossing
  • How to measure the induced voltage
  • Virtual star-point
  • The induced voltage is destroyed
  • Start procedure without sensors

 Field Oriented Control

  • Field Oriented Control
  • Current and position measurement
  • Transformation in the rotor coordinate system
  • Two current controller
  • Inverse Clarke-Park Transformation
  • State Space Vector
  • PWM with state space vector
  • State space vector modulation
  • Estimate the rotor position
  • PWM variants



Last Update: 28.01.2018

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stepper motor


field oriented control