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Modern electric trends in electric drives

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Modern electric trends in electric drives

  1. 1. Modern Trends of Electric Drives In Electric Traction System SUBMITTED BY:- SURINDER KUMAR B.TECH (E.E.) 100170593752
  2. 2. Introduction • Traction motors can use both ac/dc currents with suitable control electronics. They are operating in high voltage current. • They can widely used for vehicles, elevators, locomotives etc. • Traction motor refers to an electric motor providing the primary rotational torque of a machine. • Traction motors are used in electrically powers rail vehicles such as electric multiple units and electric locomotives.
  3. 3. Requirements of Traction System • High starting pulling effort in order to have rapid acceleration. • Equipment capable of withstanding large temporary overloads for short periods. • The locomotive should be self contained and able to run on any route. • Capability of withstanding voltage fluctuations and temporary interruption of supply. • Parallel running usually more than one motor (two or four motors) should be possible.
  4. 4. Components of an AC Locomotive
  5. 5. Electronic Speed Control Method for DC Motor • Compared to the electric and electro-mechanical systems of speed control, the electronic methods have  Higher accuracy  Greater reliability  Quick response  Higher efficiency
  6. 6. Recent Trends in Electrical Traction System Multi-Stage Converters: • The multi-stage converter has a chain of 4 converters per phase (4- Stage Converter), with a “Main converter” that manages more than 80% of the total power. • Three “Slave converters” that take the rest of the power (less than 20%). • It can generate almost perfect current & voltage waveforms, because it is modulated by amplitude instead of pulse-width modulation.
  7. 7. Continued….. • It can generate near sinusoidal voltages with only fundamental frequency switching. • It have almost no electromagnetic interference of common mode voltages. • They are suitable for large volt-ampere rated motor drives & high voltages and it is lower frequency devices.
  8. 8. Multistage Converter • S2 and S1’ are switched on the output is –V dc. • Either pair S1 and S2 or S1’ and S2’ are on the output is zero. • S1 and S2’ are on the output is +V dc.
  9. 9. 4 Level Multi Stage Converter Main components of Multistage Converter
  10. 10. 2-level converter • The two-level converter is the simplest type of three-phase voltage-source converter. • It is a six pulse bridge in which the thyristors have been replaced by IGBTs with inverse-parallel diodes. • The voltage at the AC output of each phase is switched between two discrete voltage levels. • Corresponding to the electrical potentials of the positive and negative DC terminals. • When the upper of the two valves in a phase is turned on, the AC output terminal is connected to the positive DC terminal. • Resulting in an output voltage of +½ Ud with respect to the midpoint potential of the converter. • When the lower valve in a phase is turned on, the AC output terminal is connected to the negative DC terminal, resulting in an output voltage of -½ Ud.
  11. 11. 2-level converter
  12. 12. Three Level Converter • To improve the poor harmonic performance of the two-level converter, some systems have been built with three level converters. • Three-level converters can only two discrete voltage levels at the AC terminal of each phase: +½ Ud, 0 and -½ Ud. • A common type of three-level converter is the diode-clamped (or neutral-point- clamped) converter, where each phase contains four IGBT valves. • Each rated at half of the DC line to line voltage, along with two clamping diode valves. • The DC capacitor is split into two series-connected branches, with the clamping diode. • To obtain a positive output voltage (+½ Ud) the top two IGBT valves are turned on. • To obtain a negative output voltage (-½ Ud) the bottom two IGBT valves are turned on • To obtain zero output voltage the middle two IGBT valves are turned on
  13. 13. Three Level Converter
  14. 14. Modular Multi-Level Converter • The MMC differs from other types of converters. • In that the current flows continuously in all six valves of the converter throughout the mains-frequency cycle. • As a result, concepts such as “on-state” and “off-state” have no meaning in the MMC. • The direct current splits equally into the three phases. • The alternating current splits equally into the upper and lower valve of each phase. • The current in each valve is therefore related to the direct current Id and alternating current Iac as follows:
  15. 15. Modular Multi-Level Converter
  16. 16. Voltage Distribution in Multistage Converter
  17. 17. Power Distribution in Multistage Converter
  18. 18. Advantages • It can generate perfect current & voltages waveforms. • The power losses into the machine due to harmonic current are also eliminates. • Reducing power losses at minimum value. • Power rating of semiconductor is very small. • Multi stage converter working at low switching frequency. • Operation is fast & quick response.
  19. 19. Applications • Active power filters. • Sinusoidal current rectifiers. • Machine drives. • Power factor compensators. • Back to back frequency link system. • Traction drive system.

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