Three Phase Inverter Motors

1. Three Phase Inverter Motors Ben Kemink

2. Three Phase Inverter Motor At the end of this training session you will have learned; • There are different three-phase measurements. • Pulse Width Modulation. • Inverter Driven Applications mess-up with Period Time T.

3. Three Phase Systems A One-Phase System, also called a Single-Phase (SP) System works very much similar to a DC network and can be considered so far at any particular moment in time. Electrical Systems comprising two or more phases are also called Multi-Phase or Poly-Phase (PP) systems. The voltage amplitudes and frequencies in the individual system circuits are the same, but they have definite phase differences.

4. Why Poly-Phase? The technical complications and economical investments are small compared to the enormous advantages of a Poly-Phase system: 1. Same size generator or motor, higher output. 2. Same energy transmission less copper required. 3. PP motors have uniform torque, SP have pulsating torque *). 4. PP motors are self-starting, SP are not *). 5. Polyphase generators work fine parallel, SP not. *) Single Phase commutator motors are exception.

5. Why 3 Phase and not 7?

6. Three Phase is ideal Source: Advanced Electrical Technology by H.Cotton

7. Three-Phase Three-Wire Total Power calculation based on Two-Watt-meter method 3 wires – 1 = 2 power meters required

8. Three-Phase Four-Wire 4 wires - 1 = 3 Watt meters are required

9. Three-Voltage Three-Current Calculation based on Two-Watt meter method. Third Phase measurements are added.

10. Three-Phase Three-Wire with PT & CT

11. Introduction • What is Three phase? • Three phase = three signals • Phase shift: 1200 Figure 1: Phase shift 1200

12. Pulse Width Modulation of a Sine Wave

13. Demonstration circuit Demonstration circuit consists of: • Frequency inverter; • 3-Phase Electromotor; • Power meter; Figure 2: Demonstration circuit

14. L1(mains) Demonstration circuit • Freq. inverter • Step 1: AC → DC • Step 2: DC → 3-Phase T T Control unit 0 Hz → 50 Hz Figure 3: Block diagram 1phase inverter

15. Demonstration circuit • AC → DC • Performed by rectifier; • DC-signal is smoothened by capacitor; • In 3phase mains the output of the rectifiers is connected to the same capacitor; • Freq. inverter Step 1: rectifying Example: Single phase rectifying t → Figure 4: rectifier

16. U t Demonstration circuit • Freq. inverter • Step 2: regeneration of 3-Phase-signals • Six switches • Generate periodic pulse-trains; • Insulated Gate Bipolair Transistor (IGBT); • High frequency switches; New Period T t Figure 5: Inverter step 2: regeneration of AC-signals

17. Demonstration circuit • Freq. inverter • YEF-HQ Test Motor Figure 6: Output of Freq. Inverter: 1-phase, current (green) / voltage (yellow)

18. U U V V W W Running the motor CW • Direction • Direction (CCW or CW) • Can be changed by manipulating the pulses CCW

19. U U V V W W Running the motor T • Speed • Depends on the switching frequency Slow Two times faster T

20. Faster 1s time window Running the motor • Speed: voltage (yellow) and current (green) • Slow • 1s time window Figure 7: Output of Freq. Inverter at different speeds

21. Now you have learned; • There are different three-phase measurements. • What Pulse Width Modulation is. • Why Inverters mess-up with Period Time T.

22. Thank you for your attention