Variable Speed Drive (VSD)

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24 Νοε 2013 (πριν από 3 χρόνια και 11 μήνες)

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Variable Speed Drive (VSD)


Frequency Inverter Application
-

General

BITZER Kühlmaschinenbau GmbH

2013

BITZER //
Climatechno

2013// Page
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



BITZER //
Climatechno

2013// Page
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



Re
duced starting current with full motor torque





No start
unloader

required





Reduced mechanical load





Minimized danger of liquid slugging during start
-
up


BITZER //
Climatechno

2013// Page
4

The Use of Frequency Inverters with

BITZER 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

BITZER //
Climatechno

2013// Page
5

The Use of Frequency Inverters with

BITZER Compressors


General

average
evap. temp.
with fixed
speed
compressor

VSD

VSD with suction pressure control
-

vs.
-

fixed speed // Example

0.1 bar

Source:
FrigoPack

(www.frigokimo.com)

BITZER //
Climatechno

2013// Page
6


-

4
°
C


-
18
°
C


to
-

12C

Δt
14 K

The Use of Frequency Inverters with

BITZER Compressors


General

Why Frequency Inverter?

/
Fixed
frequency rack system


Setpoint

BITZER //
Climatechno

2013// Page
7

The Use of Frequency Inverters with

BITZER Compressors


General

Why Frequency Inverter?

/
Infinite capacity control

to
-
12
°
C


Δt
4K

Setpoint

BITZER //
Climatechno

2013// Page
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)


BITZER //
Climatechno

2013// Page
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

BITZER //
Climatechno

2013// Page
10

Frequency Inverter


Basic Principle

Rectifier

Transition

Circuit

Inverter

(IGBT’s)

Control Circuit

Motor

3~

Control Voltage

L1

L2

L3

P
ulse
W
idth
M
odulation

Sine wave throttles

(depending
on
FI output quality
)

Net work throttles

(recommended


due to EMC)

(Capacitors)

BITZER //
Climatechno

2013// Page
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

BITZER //
Climatechno

2013// Page
12

The Use of Frequency Inverters with

BITZER Compressors


General

n

Motor

=

f

x 60

Number of pole pairs



n
Slip

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



BITZER //
Climatechno

2013// Page
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


M

=

[Nm]

P

= U
x

I
x


3
x

cos
j

[W]

P

x

9,55

n (1/min)

Mechanical side:

Electrical side:

BITZER //
Climatechno

2013// Page
14

Requirements on Motor Characteristics

and Layout of Frequency Inverter

Above max. voltage (without voltage
adaption):



Ratio U/f declines



Absorbed current rises



Danger of motor (temperature) overload!



~
constant

M

=

[Nm]

U

x

I

x


3
x

cos
j

x

9,55

n

Mechanical side and electrical side combined:


„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)

BITZER //
Climatechno

2013// Page
15

Frequency Inverter


Voltage & Frequency

with Constant Torque (Supply 400V
-
3
-
50 Hz)

Voltage

0

100

200

300

400

0

10

20

30

40

50

60

70

80

Frequency

[Hz]

87

[V]

Nominal Motor
Voltage
:

A

A: 400 V
-
3
-
50 Hz
40P / 40D


B

B:
380
V
-
3
-
60
Hz
35P / 35D

C

C: 230 V
-
3
-
50 Hz
40S

Examples

Speed
range

limit

for


standard

recips
)

BITZER //
Climatechno

2013// Page
16

Frequency Inverter


Power & Torque

with Motor Winding Layout for 230V
-
3
-
50Hz

0

20

40

60

80

100

120

140

160

180

0

10

20

30

40

50

60

70

80

Frequency

[Hz]

Torque M

[%]

0

50

100

150

200

300

350

400

Voltage [V]

230

87

Current I

Speed
range

limit

for



standard

recips
)

BITZER //
Climatechno

2013// Page
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


BITZER //
Climatechno

2013// Page
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)


BITZER //
Climatechno

2013// Page
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
M
agnitude

/
Consider length of wire in manufacturer's documentation!!

/
Possible problems
: motor noise / insulation failures


Screened wires (incl. grounding) from inverter to
motor

(
E
lectro
M
agnetic
C
ompatibility)


BITZER //
Climatechno

2013// Page
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


BITZER //
Climatechno

2013// Page
21

The Use of Frequency Inverters with

BITZER Compressors


General Issues

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


Open Drive Compressors

BITZER //
Climatechno

2013// Page
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

BITZER //
Climatechno

2013// Page
23

NEW ECOLINE VARISPEED



KP
-
102
-
4

CE4 Varispeed Series

BITZER //
Climatechno

2013// Page
24

0
10.000
20.000
30.000
40.000
50.000
60.000
70.000
2DES
-
3.F1Y
4FES
-
5.F1Y
4EES
-
6.F1Y
4DES
-
7.F3Y
4CES
-
9.F3Y
4VES
-
10.F4Y
4TES
-
12.F4Y
4PES
-
15.F4Y
4NES
-
20.F4Y
[W]
Cooling Capacity (R404A)
t
o
=
-
5
°
C; t
c
= 40
°
C
SGT 20
C, without liquid subcooling
25Hz

30Hz

25Hz

87Hz

87Hz

87Hz

NEW ECOLINE VARISPEED

BITZER //
Climatechno

2013// Page
25

NEW ECOLINE VARISPEED

Special Design Features (1)

Solidly flanged FI

// no vibrations

Suction gas cooled FI

// no air filter (service) needed

// no load restrictions at

high ambient temp.

Shielded motor cable

// short and preassembled

BITZER //
Climatechno

2013// Page
26

NEW ECOLINE VARISPEED

Special Design Features (2)



Easy commissioning

// FI completely parameterized

Full torque up to 87Hz

// motor delta connected

(230V
-
50Hz


400V
-
87Hz)

Up to 70% more capacity

// compared to fixed speed version

// infinite control range more than 3:1

BITZER //
Climatechno

2013// Page
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




BITZER //
Climatechno

2013// Page
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: 4..20
mA

Terminals 2 & 8: 0..10 V


BITZER //
Climatechno

2013// Page
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


BITZER //
Climatechno

2013// Page
30

NEW ECOLINE VARISPEED


Payback Period


(following example based on

previous compressor models,

but results based on NEW ECOLINE

expected to be similar)

BITZER //
Climatechno

2013// Page
31

VARISPEED Compressors // Payback Period
(1)

Example:


Cooling capacity 37kW + 5kW reserves

Conditions:


R404A; t
o
=
-
8
°
C;
t
c
= 20
°
C … 45
°
C;
Δ
t
oh
= 20K;
D
t
cu
=10K

Installation place:

Berlin




Rack

3x
4DC
-
7.2Y

2x
4EC
-
6.2Y

+ 1x
4EC
-
6.F1Y

Number of comp.

3

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



BITZER //
Climatechno

2013// Page
32

Type

Qo
[kWh]

P in
[kWh]

Annual

COP

4DC
-
7.2Y Rack (steps)

324120

84482

3,84

4EC Rack (infinite)

324120

79445

4,08

Results:

6 % higher annual
COP
(system)!






Payback period below 2

years!

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



BITZER //
Climatechno

2013// Page
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?