Three Phase Inverter Motors Ben Kemink

FORESIGHT INNOVATION QUALITY 2 At the end of this training session you will have learned; 1.There are different three-phase measurements. 2.Pulse Width Modulation. 3.Inverter Driven Applications mess-up with Period Time T. Three Phase Inverter Motor

FORESIGHT INNOVATION QUALITY 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.

FORESIGHT INNOVATION QUALITY 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.

FORESIGHT INNOVATION QUALITY 5 Why 3 Phase and not 7?

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

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

FORESIGHT INNOVATION QUALITY 8 Three-Phase Four-Wire 4 wires - 1 = 3 Watt meters are required

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

FORESIGHT INNOVATION QUALITY 10 Three-Phase Three-Wire with PT & CT

FORESIGHT INNOVATION QUALITY 11 Introduction What is Three phase? Three phase = three signals Phase shift:120 0 Figure 1: Phase shift 120 0

FORESIGHT INNOVATION QUALITY 12 Pulse Width Modulation of a Sine Wave

FORESIGHT INNOVATION QUALITY 13 Demonstration circuit Demonstration circuit consists of:  Frequency inverter;  3-Phase Electromotor;  Power meter; Figure 2: Demonstration circuit

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

FORESIGHT INNOVATION QUALITY 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; t → Example: Single phase rectifying Freq. inverterStep 1: rectifying Figure 4: rectifier

FORESIGHT INNOVATION QUALITY 16 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; U t t Figure 5: Inverter step 2: regeneration of AC-signals New Period T

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

FORESIGHT INNOVATION QUALITY 18 Running the motor Direction  Direction (CCW or CW) Can be changed by manipulating the pulses CW CCW U V W U V W

FORESIGHT INNOVATION QUALITY 19 Running the motor Speed Depends on the switching frequency Slow Two times faster U V W U V W T T

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

FORESIGHT INNOVATION QUALITY 21 Now you have learned; 1.There are different three-phase measurements. 2.What Pulse Width Modulation is. 3.Why Inverters mess-up with Period Time T.

FORESIGHT INNOVATION QUALITY 22 Thank you for your attention