EDS applications

1. Air conditioning
2. Washing machine
3. Electric Vehicle
4. Steel rolling mills
5. Pulp and paper mill
6. Power supply fan
7. Food processor

The structure of EDS

1. Electric motor
2. Mechanical load
3. Power modulator
4. Power supply
5. Sensing circuit
6. Control circuit

Types of electric motors

1. DC motor:
   • Separately excited
   • Shunt
   • Series
   • Compound (long/short)
   • Permanent magnet
2. AC motor:
   • Induction (Squirrel Cage, Wound Rotor, linear)
   • Synchronous (wound, permanent magnet)
3. Special motors:
   • Brushless DC (less maintenance)
   • Stepper (for robotics and control)
   • Switched reluctance (space application - rotor light and less inertia)

Types of power modulators

1. DC-DC Choppers:
   • step-down (buck)
   • Step-up (boost)
   • Step-up & step-down (buck-boost)
2. AC-DC Rectifiers:
   • diode rectifier
   • half-controlled rectifier
   • fully-controlled rectifier
   • Transformer with tap-changer + diode rectifier
   • Diode rectifier + DC-DC chopper
3. DC-AC Inverters:
   • Voltage source inverter (VSI)
   • Current source inverter (CSI)
4. AC-AC converter:
   • AC voltage regulator (fixed $f$ & V $\rightarrow$ fixed $f$ & variable V)
   • Cycloconverter (fixed $f$ & V $\rightarrow$ variable $f$ & V)

Types of power supplies

1. 1PH & 3PH 50Hz/60Hz 240/415V
2. High power drive - 33kV, 6.6kV, 11kV
3. Air craft 400Hz
4. Electric traction (i.e. electric trains) - 1PH 6.25kV, 12.5kV, 25kV, 50kV
5. DC power supply:
   • Solar power
   • Batteries

Advantages of electric drives

1. No mechanical parts (no gears)
2. Four quadrant operation
3. No pollution (sound, emission)
4. High efficiency
5. Wide range of torque, speed, and power: Scalable (computer fan10W, mixer/grinder 100W, AC kW, industrial drives 100kW, locomotive MW)

Four quadrant operation

$P=T \cdot \omega_m$

• if $P > 0$ power flow from PS to M

• if $P < 0$ power flow from M to PS

  

Quadrant operation:

I : $T \gt 0$ & $\omega_m \gt 0$ $\longleftrightarrow$ forward motoring
II : $ T \lt 0 $ & $\omega_m \gt 0$ $\longleftrightarrow$ forward breaking
III: $T \lt 0$ & $\omega_m \lt 0$ $\longleftrightarrow$ reverse motoring
IV: $T \gt 0$ & $\omega_m \lt 0$ $\longleftrightarrow$ reverse breaking

Load torque

$$\begin{equation} T_L = T_F + T_L^*\end{equation}$$

where $ T_L^*$ is the physical load torque and $T_F$ is the motor friction torque.

what are the components of load torque ?

The friction torque \eqref{TF} is composed of a number of motor related frictions. Some are constant, some are short lived, and others related to speed.

$$\begin{equation}T_F = T_S + T_C + T_V + T_W\label{TF}\end{equation}$$

• Static friction ($T_S$) - exists in static to low speed condition
• Coulomb friction ($T_C$) - independent of speed
• Viscous friction ($T_V$) - linearly proportional to speed
• Windage friction ($T_W$) - proportional to the square of speed ($\omega^2$)

Notes