1. Variable Speed Drive (VSD) Frequency Inverter Application - General
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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 (

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?