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  1. Variable Speed Drive (VSD)Frequency Inverter Application - General BITZER Kühlmaschinenbau GmbH 2013

  2. Variable Speed Drive //Frequency Inverter Application - General • Contents • Pros & cons • Basic principle & function • Requirements on motor characteristics and layout of frequency inverter • Selection criteria (inverter, cables) • Special considerations for open drive compressors • Semi-hermetic compressor with integrated FI

  3. The Use of Frequency Inverters withBITZER Compressors – General • Why Frequency Inverter? Possibility for infinite speed modulation with 3-phase asynchronous motors Pros: • Infinite capacity control  Higher part load energy efficiency  Without additional pressure fluctuation Steady suction pressure and TX valve operation Smaller temperature differences at HX (higher suction pressure, lower discharge pressure) • Trans-synchronous operation  Smaller compressor Enhanced capacity control range • Soft start function  Reduced starting current with full motor torque  No start unloader required  Reduced mechanical load Minimized danger of liquid slugging during start-up

  4. The Use of Frequency Inverters withBITZER Compressors – General Speed control of compressor Energy savings: 15% Page 113 (of 270) http://www.umweltbundesamt.de/uba-info-medien/mysql_medien.php?anfrage=Kennummer&Suchwort=3743

  5. The Use of Frequency Inverters withBITZER Compressors – General VSD with suction pressure control - vs.- fixed speed // Example 0.1 bar VSD average evap. temp. with fixed speed compressor Source: FrigoPack (www.frigokimo.com)

  6. The Use of Frequency Inverters withBITZER Compressors – General • Why Frequency Inverter? • Fixed frequency rack system Setpoint - 4°C to - 12C -18°C Δt14 K

  7. The Use of Frequency Inverters withBITZER Compressors – General • Why Frequency Inverter? • Infinite capacity control to -12°C Setpoint Δt 4K

  8. The Use of Frequency Inverters withBITZER Compressors – General • Cons: • Power consumption at 50 Hz slightly higher compared to direct operation (losses in power electronics, compressor motor) • Due to wide speed range risk of resonances and vibrations in pipe work • Higher efforts in projecting and selection of components • Very often higher installation costs (higher investments)

  9. Variable Speed Drive //Frequency Inverter Application - General • Contents • Pros & cons • Basic principle & function • Requirements on motor characteristics and layout of frequency inverter • Selection criteria (inverter, cables) • Special considerations for open drive compressors • Semi-hermetic compressor with Integrated FI

  10. Frequency Inverter – Basic Principle Pulse Width Modulation Transition L1 Inverter (IGBT’s) Motor Circuit Rectifier L2 3~ L3 (Capacitors) Control Circuit Control Voltage Net work throttles(recommended due to EMC) Sine wave throttles(depending on FI output quality)

  11. Variable Speed Drive //Frequency Inverter Application - General • Contents • Pros & cons • Basic principle & function • Requirements on motor characteristics and layout of frequency inverter • Selection criteria (inverter, cables) • Special considerations for open drive compressors • Semi-hermetic compressor with Integrated FI

  12. The Use of Frequency Inverters withBITZER Compressors – General • Function of Frequency Inverter • Frequency Modulation • U / f - Operation: Inverter must control voltage and frequency in a constant ratio Motor torque required remains constant with positive displacement compressors • Consequences if no voltage adaptation  Increased motor current •  Risk of motor overheating •  Decrease of motor torque f x 60 – n Slip nMotor= Number of pole pairs

  13. Px 9,55 M = P = U x I xÖ3 xcosj [W] [Nm] n (1/min) Requirements on Motor Characteristics and Layout of Frequency Inverter • With Positive Displacement Compressors (Recips, Scroll, Screws) • Torqueremains “constant" with speed change • Power absorbed changes approx. proportional to the speed Mechanical side: Electrical side:

  14. ~ constant UxIxÖ3 xcosjx 9,55 M = [Nm] n Requirements on Motor Characteristics and Layout of Frequency Inverter Mechanical side and electrical side combined: • Above max. voltage (without voltage adaption): • Ratio U/f declines • Absorbed current rises • Danger of motor (temperature) overload! • „Demanded“ torque (M) = remains constant from mechanical side • U/n~ U/f = constant (by inverter controller) •  Current “I” remains (almost) constant (with constant operating conditions, e.g. SST, SCT)

  15. Speed rangelimitforstandardrecips) A B C A: 400 V-3-50 Hz 40P / 40D B: 380 V-3-60 Hz 35P / 35D C: 230 V-3-50 Hz 40S Frequency Inverter − Voltage & Frequency with Constant Torque (Supply 400V-3-50 Hz) Examples 400 Voltage [V] 300 200 Nominal Motor Voltage: 100 0 Frequency 0 10 20 30 40 50 60 70 80 87 [Hz]

  16. Speed rangelimitforstandardrecips) Frequency Inverter – Power & Torque with Motor Winding Layout for 230V-3-50Hz [%] 180 160 140 120 Current I 100 Torque M 80 Power P 60 40 20 0 Frequency [Hz] 0 10 20 30 40 50 60 70 80 87 Voltage [V] 0 50 100 150 200 230 300 350 400

  17. Variable Speed Drive //Frequency Inverter Application - General • Contents • Pros & cons • Basic principle & function • Requirements on motor characteristics and layout of frequency inverter • Selection criteria (inverter, cables) • Special considerations for open drive compressors • Semi-hermetic compressor with Integrated FI

  18. The Use of Frequency Inverters with BITZER Compressors – General • General Selection Criteria • Frequency and Speed Ranges • Depending on compressor technology and application • Reciprocating, scroll, screw compressor • Open drive, semi-hermetic, hermetic • Motor layout & power supply • Operating conditions, refrigerant, thermal load • Inverter selection formax. operating current, see technical data (e.g. KP-100) • Increased starting torque during starting phase • Example for piston compressors • depending on number of cylinders (2 // 4 // 6) factors (2 // 1,6 // 1,5)

  19. The Use of Frequency Inverters with BITZER Hermetics & Semi-hermetics • Special Requirements on Frequency Inverter and Connection Wires • Critical Frequency and Speed Ranges • Dependent on operating conditions resonances may occur in certain frequency (speed) ranges • Examination by tests under real conditions • critical frequency ranges must be skipped by adequate programming of the inverter • Note of Voltage Magnitude • Consider length of wire in manufacturer's documentation!! • Possible problems: motor noise / insulation failures • Screened wires (incl. grounding) from inverter to motor (Electro Magnetic Compatibility)

  20. Variable Speed Drive //Frequency Inverter Application - General • Contents • Pros & cons • Basic principle & function • Requirements on motor characteristics and layout of frequency inverter • Selection criteria (inverter, cables) • Special considerations for open drive compressors • Semi-hermetic compressor with Integrated FI

  21. The Use of Frequency Inverters with BITZER Compressors – General Issues Open Drive Compressors • Selection Criteria for Motor and Inverter • Motor selection according to manufacturer's requirementsSpecial Criteria: • Air flow is not in proportion to the motor speed • increased power with trans-synchronous operation • possibly insufficient cooling with sub-synchronous operation • Motor Selection / Application Range • dependent on inverter design and quality of sine wave additional spare capacity for the motor may be required • Inverter selection according to specification of motor and inverter manufacturers

  22. Variable Speed Drive //Frequency Inverter Application - General • Contents • Pros & cons • Basic principle & function • Requirements on motor characteristics and layout of frequency inverter • Selection criteria (inverter, cables) • Special considerations for open drive compressors • Semi-hermetic compressor with Integrated FI

  23. NEW ECOLINE VARISPEED KP-102-4 CE4 Varispeed Series

  24. NEW ECOLINE VARISPEED 87Hz 87Hz 87Hz 25Hz 30Hz 25Hz

  25. NEW ECOLINE VARISPEEDSpecial Design Features (1) Shielded motor cable// short and preassembled Solidly flanged FI // no vibrations Suction gas cooled FI // no air filter (service) needed // no load restrictions at high ambient temp.

  26. NEW ECOLINE VARISPEEDSpecial Design Features (2) Up to 70% more capacity// compared to fixed speed version // infinite control range more than 3:1 Full torque up to 87Hz// motor delta connected(230V-50Hz  400V-87Hz) Easy commissioning// FI completely parameterized

  27. NEW ECOLINE VARISPEEDCompressor Installation (Example with CE3-F1) • Shielded connection cable between inverter and compressor is pre-assembled • Power supply has to be connected to frequency inverter • Check suction and discharge line for resonances under real operating conditions

  28. NEW ECOLINE VARISPEEDCompressor Installation • Operation and control // Frequency inverter F1 • The compressor/ inverter unit is controlled by an external controller. • It can be operated with factory defaults, no parameterization is required. • There are two characteristic curves preprogrammed within the inverter. Depending on the control line connection on terminal a voltage (0..10 V) or current (4..20 mA) dependent characteristic curve can be used.Terminals 1 & 8: 4..20 mA • Terminals 2 & 8: 0..10 V

  29. NEW ECOLINE VARISPEEDFailure Analysis • Generally no additional adjustment by manual control unit required • Inverter is pre-programmed to its assigned compressor • If required, pre-programmed parameter can be changed – especially in case of vibrations within the installation • Multiple frequency ranges can be masked out

  30. NEW ECOLINE VARISPEEDPayback Period(following example based on previous compressor models, but results based on NEW ECOLINE expected to be similar)

  31. VARISPEED Compressors // Payback Period (1) • Example: Cooling capacity 37kW + 5kW reservesConditions: R404A; to= -8 °C; tc= 20°C … 45°C; Δtoh= 20K; Dtcu=10KInstallation place: Berlin

  32. VARISPEED Compressors // Payback Period (3) • Annual energy consumption • To be considered: • Comparison based on constant load – variable load requirements lead to additional COP weakness of fixed speed compressor applications • Winter operation leads to additional COP weakness of fixed speed application Results:6 % higher annual COP (system)! Payback period below 2 years!

  33. Variable Speed Drive //Frequency Inverter Application - General • Contents • Pros & cons • Basic principle & function • Requirements on motor characteristics and layout of frequency inverter • Selection criteria (inverter, cables) • Special considerations for open drive compressors • Semi-hermetic compressor with Integrated FI √ √ √ √ √ √ Any Questions?