Three Phase Inverter Motors Ben Kemink Three Phase

Three Phase Inverter Motors Ben Kemink

Three Phase Inverter Motor 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. QUALITY 2 INNOVATION FORESIGHT

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. QUALITY 3 INNOVATION FORESIGHT

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. QUALITY 4 INNOVATION FORESIGHT

Why 3 Phase and not 7? QUALITY 5 INNOVATION FORESIGHT

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

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

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

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

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

Introduction n What is Three phase? Three phase = three signals n Phase shift: 1200 n QUALITY 11 INNOVATION Figure 1: Phase shift 1200 FORESIGHT

Pulse Width Modulation of a Sine Wave QUALITY 12 INNOVATION FORESIGHT

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

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

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

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

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

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

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

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

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. QUALITY 21 INNOVATION FORESIGHT

Thank you for your attention QUALITY 22 INNOVATION FORESIGHT