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Variable Speed Drive (VSD) Frequency Inverter Application - General

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Presentation on theme: "Variable Speed Drive (VSD) Frequency Inverter Application - General"— Presentation transcript:

1 Variable Speed Drive (VSD) Frequency Inverter Application - General
Print 2-5;6-10;12-17;19-22 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 with BITZER 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 with BITZER Compressors – General
Speed control of compressor Energy savings: 15% Page 113 (of 270)

5 The Use of Frequency Inverters with BITZER 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 with BITZER Compressors – General
Why Frequency Inverter? Fixed frequency rack system Setpoint - 4°C to - 12C -18°C Δt14 K

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

8 The Use of Frequency Inverters with BITZER 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 L1 Transition Inverter (IGBT’s) Motor L2 Rectifier Circuit 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 with BITZER 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 Motor = – n Slip Number of pole pairs

13 Requirements on Motor Characteristics and Layout of Frequency Inverter
With Positive Displacement Compressors (Recips, Scroll, Screws)  Torque remains “constant" with speed change  Power absorbed changes approx. proportional to the speed Mechanical side: Electrical side: M = [Nm] P = U x I x Ö3 x cosj [W] P x 9,55 n (1/min)

14 Requirements on Motor Characteristics and Layout of Frequency Inverter
Mechanical side and electrical side combined: M = [Nm] U x I x Ö3 x cosj x 9,55 n ~ constant „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) Above max. voltage (without voltage adaption): Ratio U/f declines Absorbed current rises Danger of motor (temperature) overload!

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

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

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 for max. 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 requirements Special 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 VARISPEED Special 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 VARISPEED Special 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 VARISPEED Compressor 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 VARISPEED Compressor 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: mA Terminals 2 & 8: V

29 NEW ECOLINE VARISPEED Failure 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 VARISPEED Payback 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 reserves Conditions: R404A; to= -8 °C; tc= 20°C … 45°C; Δtoh= 20K; Dtcu=10K Installation place: Berlin Rack 3x 4DC-7.2Y 2x 4EC-6.2Y + 1x 4EC-6.F1Y Number of comp. 3 Capacity max. 42,4 kW 43,9 kW Capacity min. 14,1 kW 5,6 kW Control range 33 / 66 / 100 % 12,8 … 100 % Control type steps infinite

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 Type Qo [kWh] P in [kWh] Annual COP 4DC-7.2Y Rack (steps) 324120 84482 3,84 4EC Rack (infinite) 79445 4,08 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?

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