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

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The structure of EDS

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

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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)

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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)

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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

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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)

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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