Danfoss VLT HVAC Drive FC 100 Series Design Manual
VLT® HVAC Drive Design Guide Contents
Contents
1. How to Read this Design Guide
Copyright, Limitation of Liability and Revision Rights 3
Approvals 4
Symbols 4
Abbreviations 5
Definitions 5
2. Introduction to VLT HVAC Drive
Safety 11
CE labelling 12
Air humidity 13
Aggressive Environments 14
Vibration and shock 14
VLT HVAC Drive Controls 28
PID 30
General aspects of EMC 39
Galvanic isolation (PELV) 41
PELV - Protective Extra Low Voltage 41
3
11
Control with brake function 42
Extreme running conditions 45
Safe Stop 48
3. VLT HVAC Drive Selection
Options and Accessories 51
4. How to Order
Ordering Numbers 63
5. How to Install
Mechanical Dimensions 72
Electrical Installation 79
Final Set-Up and Test 104
Additional Connections 106
DC bus connection 106
Brake Connection Option 106
Relay Connection 107
Installation of misc. connections 111
51
61
71
Safety 113
EMC-correct Installation 114
Mains supply interference/Harmonics 118
Residual Current Device
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Contents VLT® HVAC Drive Design Guide
6. Application Examples
Start/Stop 119
Pulse Start/Stop 119
Potentiometer Reference 120
Automatic Motor Adaptation (AMA) 120
Smart Logic Control Programming 120
SLC Application Example 121
BASIC Cascade Controller 122
Pump Staging with Lead Pump Alternation 123
System Status and Operation 123
Fixed Variable Speed Pump Wiring Diagram 124
Lead Pump Alternation Wiring Diagram 124
Cascade Controller Wiring Diagram 124
Start/Stop conditions 125
7. RS-485 Installation and Set-up
RS-485 Installation and Set-up 127
FC Protocol Overview 129
119
127
Network Configuration 130
FC Protocol Message Framing Structure 130
Examples
Modbus RTU Overview 135
Modbus RTU Message Framing Structure 137
How to Access Parameters 140
Examples 142
Danfoss FC Control Profile 148
8. General Specifications and Troubleshooting
General Specifications 153
Efficiency 164
Acoustic noise 165
Peak voltage on motor 165
Special Conditions 166
Alarms and warnings 167
Alarm words 171
Warning words 172
134
153
Extended status words 173
Fault messages 174
Index
2
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VLT® HVAC Drive Design Guide 1. How to Read this Design Guide
1. How to Read this Design Guide
1
VLT HVAC Drive
FC 100 Series
Software version: 2.8.x
This guide can be used with all VLT HVAC Drive frequency converters
with software version 2.8.x.
The actual software version number can be read from
par. 15-43 Software
1.1.1. Copyright, Limitation of Liability and Revision Rights
This publication contains information proprietary to Danfoss. By accepting and using this manual the user agrees that the information contained herein
will be used solely for operating equipment from Danfoss or equipment from other vendors provided that such equipment is intended for communication
with Danfoss equipment over a serial communication link. This publication is protected under the Copyright laws of Denmark and most other countries.
Danfoss does not warrant that a software program produced according to the guidelines provided in this manual will function properly in every physical,
hardware or software environment.
Although Danfoss has tested and reviewed the documentation within this manual, Danfoss makes no warranty or representation, neither expressed nor
implied, with respect to this documentation, including its quality, performance, or fitness for a particular purpose.
In no event shall Danfoss be liable for direct, indirect, special, incidental, or consequential damages arising out of the use, or the inability to use information
contained in this manual, even if advised of the possibility of such damages. In particular, Danfoss is not responsible for any costs, including but not
limited to those incurred as a result of lost profits or revenue, loss or damage of equipment, loss of computer programs, loss of data, the costs to substitute
these, or any claims by third parties.
Version
.
Danfoss reserves the right to revise this publication at any time and to make changes to its contents without prior notice or any obligation to notify former
or present users of such revisions or changes.
MG.11.B7.02 - VLT® is a registered Danfoss trademark
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1. How to Read this Design Guide VLT® HVAC Drive Design Guide
1.1.2. Available Literature
1
- Operating Instructions MG.11.Ax.yy provide the neccessary information for getting the frequency converter up and running.
- Design Guide MG.11.Bx.yy entails all technical information about the frequency converter and customer design and applications.
- Programming Guide MG.11.Cx.yy provides information on how to programme and includes complete parameter descriptions.
- Mounting Instruction, Analog I/O Option MCB109, MI.38.Bx.yy
-
PC-based Configuration Tool MCT 10, MG.10.Ax.yy enables the user to configure the frequency converter from a Windows
ment.
- Danfoss VLT Energy Box software at
- VLT 6000 HVAC Application Booklet, MN.60.Ix.yy
- Operating Instructions VLT HVAC Drive BACnet, MG.11.Dx.yy
- Operating Instructions VLT HVAC Drive Profibus, MG.33.Cx.yy.
- Operating Instructions VLT HVAC Drive Device Net, MG.33.Dx.yy
- Operating Instructions VLT HVAC Drive LonWorks, MG.11.Ex.yy
- Operating Instructions VLT HVAC Drive High Power, MG.11.Fx.yy
- Operating Instructions VLT HVAC Drive Metasys, MG.11.Gx.yy
x = Revision number
yy = Language code
Danfoss technical literature is also available online at
www.danfoss.com/BusinessAreas/DrivesSolutions/Documentations/Technical+Documentation.htm
www.danfoss.com/BusinessAreas/DrivesSolutions
then choose PC Software Download
.
™
based PC environ-
1.1.3. Approvals
1.1.4. Symbols
Symbols used in this guide.
NB!
Indicates something to be noted by the reader.
Indicates a general warning.
Indicates a high-voltage warning.
* Indicates default setting
4
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VLT® HVAC Drive Design Guide 1. How to Read this Design Guide
1.1.5. Abbreviations
1
Alternating current AC
American wire gauge AWG
Ampere/AMP A
Automatic Motor Adaptation AMA
Current limit I
Degrees Celsius °C
Direct current DC
Drive Dependent D-TYPE
Electro Magnetic Compatibility EMC
Electronic Thermal Relay ETR
drive FC
Gram g
Hertz Hz
Kilohertz kHz
Local Control Panel
Meter m
Millihenry Inductance mH
Milliampere mA
Millisecond ms
Minute min
Motion Control Tool MCT
Nanofarad nF
Newton Meters Nm
Nominal motor current I
Nominal motor frequency f
Nominal motor power P
Nominal motor voltage U
Parameter par.
Protective Extra Low Voltage PELV
Printed Circuit Board PCB
Rated Inverter Output Current I
Revolutions Per Minute RPM
Regenerative terminals Regen
Second s
Synchronous Motor Speed n
Torque limit T
Volts V
LIM
M,N
M,N
M,N
M,N
INV
s
LIM
1.1.6. Definitions
Drive:
I
VLT,MAX
The maximum output current.
I
VLT,N
The rated output current supplied by the frequency converter.
U
VLT, MAX
The maximum output voltage.
Input:
Control command
You can start and stop the connected motor by means of
LCP and the digital inputs.
Functions are divided into two groups.
Functions in group 1 have higher priority than functions in
group 2.
Motor:
Group 1
Group 2
Reset, Coasting stop, Reset and Coasting stop, Quickstop, DC braking, Stop and the "Off" key.
Start, Pulse start, Reversing, Start reversing, Jog and
Freeze output
f
JOG
The motor frequency when the jog function is activated (via digital terminals).
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1. How to Read this Design Guide VLT® HVAC Drive Design Guide
f
M
The motor frequency.
1
f
MAX
The maximum motor frequency.
f
MIN
The minimum motor frequency.
f
M,N
The rated motor frequency (nameplate data).
I
M
The motor current.
I
M,N
The rated motor current (nameplate data).
n
M,N
The rated motor speed (nameplate data).
P
M,N
The rated motor power (nameplate data).
T
M,N
The rated torque (motor).
U
M
The instantaneous motor voltage.
U
M,N
The rated motor voltage (nameplate data).
Break-away torque
η
VLT
The efficiency of the frequency converter is defined as the ratio between the power output and the power input.
Start-disable command
A stop command belonging to the group 1 control commands - see this group.
Stop command
See Control commands.
6
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VLT® HVAC Drive Design Guide 1. How to Read this Design Guide
References:
Analog Reference
A signal transmitted to the analog inputs 53 or 54, can be voltage or current.
Bus Reference
A signal transmitted to the serial communication port (FC port).
Preset Reference
A defined preset reference to be set from -100% to +100% of the reference range. Selection of eight preset references via the digital terminals.
Pulse Reference
A pulse frequency signal transmitted to the digital inputs (terminal 29 or 33).
Ref
MAX
Determines the relationship between the reference input at 100% full scale value (typically 10 V, 20mA) and the resulting reference. The maximum
reference value set in par. 3-03.
Ref
MIN
Determines the relationship between the reference input at 0% value (typically 0V, 0mA, 4mA) and the resulting reference. The minimum reference value
set in par. 3-02.
Miscellaneous:
Analog Inputs
The analog inputs are used for controlling various functions of the frequency converter.
There are two types of analog inputs:
Current input, 0-20 mA and 4-20 mA
Voltage input, 0-10 V DC.
1
Analog Outputs
The analog outputs can supply a signal of 0-20 mA, 4-20 mA, or a digital signal.
Automatic Motor Adaptation, AMA
AMA algorithm determines the electrical parameters for the connected motor at standstill.
Brake Resistor
The brake resistor is a module capable of absorbing the brake power generated in regenerative braking. This regenerative braking power increases the
intermediate circuit voltage and a brake chopper ensures that the power is transmitted to the brake resistor.
CT Characteristics
Constant torque characteristics used for screw and scroll refrigeration compressors.
Digital Inputs
The digital inputs can be used for controlling various functions of the frequency converter.
Digital Outputs
The frequency converter features two Solid State outputs that can supply a 24 V DC (max. 40 mA) signal.
DSP
Digital Signal Processor.
Relay Outputs:
The frequency converter features two programmable Relay Outputs.
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1. How to Read this Design Guide VLT® HVAC Drive Design Guide
ETR
Electronic Thermal Relay is a thermal load calculation based on present load and time. Its purpose is to estimate the motor temperature.
1
GLCP:
Graphical Local Control Panel (LCP102)
Initialising
If initialising is carried out (par. 14-22), the programmable parameters of the frequency converter return to their default settings.
Intermittent Duty Cycle
An intermittent duty rating refers to a sequence of duty cycles. Each cycle consists of an on-load and an off-load period. The operation can be either
periodic duty or none-periodic duty.
LCP
The Local Control Panel (LCP) makes up a complete interface for control and programming of the frequency converter. The control panel is detachable
and can be installed up to 3 metres from the frequency converter, i.e. in a front panel by means of the installation kit option.
The Local Control Panel is available in two versions:
- Numerical LCP101 (NLCP)
- Graphical LCP102 (GLCP)
lsb
Least significant bit.
MCM
Short for Mille Circular Mil, an American measuring unit for cable cross-section. 1 MCM 0.5067 mm
2
.
msb
Most significant bit.
NLCP
Numerical Local Control Panel LCP101
On-line/Off-line Parameters
Changes to on-line parameters are activated immediately after the data value is changed. Changes to off-line parameters are not activated until you enter
[OK] on the LCP.
PID Controller
The PID controller maintains the desired speed, pressure, temperature, etc. by adjusting the output frequency to match the varying load.
RCD
Residual Current Device.
Set-up
You can save parameter settings in four Set-ups. Change between the four parameter Set-ups and edit one Set-up, while another Set-up is active.
SFAVM
Switching pattern called
Slip Compensation
The frequency converter compensates for the motor slip by giving the frequency a supplement that follows the measured motor load keeping the motor
speed almost constant..
Stator Flux oriented Asynchronous V ector M odulation (par. 14-00).
Smart Logic Control (SLC)
The SLC is a sequence of user defined actions executed when the associated user defined events are evaluated as true by the SLC.
8
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VLT® HVAC Drive Design Guide 1. How to Read this Design Guide
Thermistor:
A temperature-dependent resistor placed where the temperature is to be monitored (frequency converter or motor).
Trip
A state entered in fault situations, e.g. if the frequency converter is subject to an over-temperature or when the frequency converter is protecting the
motor, process or mechanism. Restart is prevented until the cause of the fault has disappeared and the trip state is cancelled by activating reset or, in
some cases, by being programmed to reset automatically. Trip may not be used for personal safety.
Trip Locked
A state entered in fault situations when the frequency converter is protecting itself and requiring physical intervention, e.g. if the frequency converter is
subject to a short circuit on the output. A locked trip can only be cancelled by cutting off mains, removing the cause of the fault, and reconnecting the
frequency converter. Restart is prevented until the trip state is cancelled by activating reset or, in some cases, by being programmed to reset automatically.
Trip locked may not be used for personal safety.
VT Characteristics
Variable torque characteristics used for pumps and fans.
plus
VVC
If compared with standard voltage/frequency ratio control, Voltage Vector Control (VVC
reference is changed and in relation to the load torque.
60° AVM
Switching pattern called 60°
Asynchronous Vector Modulation (See par. 14-00).
plus
) improves the dynamics and the stability, both when the speed
1.1.7. Power Factor
1
The power factor is the relation between I1 and I
The power factor for 3-phase control:
The power factor indicates to which extent the frequency converter im-
poses a load on the mains supply.
The lower the power factor, the higher the I
formance.
In addition, a high power factor indicates that the different harmonic currents are low.
The frequency converters' built-in DC coils produce a high power factor, which minimises the imposed load on the mains supply.
.
RMS
for the same kW per-
RMS
Power factor
I
cos
×
1
=
I
RMS
I
RMS
2
=
I
1
=
ϕ1
+
=
I
3×U×
3×U×
I
1
I
RMS
2
2
I
+
5
7
I
1×
since cos
+..+
COS
I
RMS
ϕ1=1
ϕ
2
I
n
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2. Introduction to VLT HVAC Drive VLT® HVAC Drive Design Guide
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VLT® HVAC Drive Design Guide 2. Introduction to VLT HVAC Drive
2. Introduction to VLT HVAC Drive
2.1. Safety
2.1.1. Safety note
The voltage of the frequency converter is dangerous whenever connected to mains. Incorrect installation of the motor, frequency
converter or fieldbus may cause damage to the equipment, serious personal injury or death. Consequently, the instructions in this
manual, as well as national and local rules and safety regulations, must be complied with.
Safety Regulations
1. The frequency converter must be disconnected from mains if repair work is to be carried out. Check that the mains supply has been disconnected
and that the necessary time has passed before removing motor and mains plugs.
2. The [STOP/RESET] key on the control panel of the frequency converter does not disconnect the equipment from mains and is thus not to be
used as a safety switch.
3. Correct protective earthing of the equipment must be established, the user must be protected against supply voltage, and the motor must be
protected against overload in accordance with applicable national and local regulations.
4. The earth leakage currents are higher than 3.5 mA.
5. Protection against motor overload is set by par. 1-90
(default value) or data value [ETR warning]. Note: The function is initialised at 1.16 x rated motor current and rated motor frequency. For the
North American market: The ETR functions provide class 20 motor overload protection in accordance with NEC.
6. Do not remove the plugs for the motor and mains supply while the frequency converter is connected to mains. Check that the mains supply has
been disconnected and that the necessary time has passed before removing motor and mains plugs.
7. Please note that the frequency converter has more voltage inputs than L1, L2 and L3, when load sharing (linking of DC intermediate circuit) and
external 24 V DC have been installed. Check that all voltage inputs have been disconnected and that the necessary time has passed before
commencing repair work.
Installation at High Altitudes
Motor Thermal Protection
. If this function is desired, set par. 1-90 to data value [ETR trip]
2
By altitudes above 2 km, please contact Danfoss regarding PELV.
Warning against Unintended Start
1. The motor can be brought to a stop by means of digital commands, bus commands, references or a local stop, while the frequency converter
is connected to mains. If personal safety considerations make it necessary to ensure that no unintended start occurs, these stop functions are
not sufficient.
2. While parameters are being changed, the motor may start. Consequently, the stop key [STOP/RESET] must always be activated; following which
data can be modified.
3. A motor that has been stopped may start if faults occur in the electronics of the frequency converter, or if a temporary overload or a fault in
the supply mains or the motor connection ceases.
Warning:
Touching the electrical parts may be fatal - even after the equipment has been disconnected from mains.
Also make sure that other voltage inputs have been disconnected, such as external 24 V DC, load sharing (linkage of DC intermediate circuit), as well as
the motor connection for kinetic back up. Refer to
VLT® HVAC Drive Operating Instructions MG.11.Ax.yy
for further safety guidelines.
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2. Introduction to VLT HVAC Drive VLT® HVAC Drive Design Guide
2.1.2. Caution
Caution
The frequency converter DC link capacitors remain charged after power has been disconnected. To avoid an electrical shock hazard, disconnect the
frequency converter from the mains before carrying out maintenance. Wait at least as follows before doing service on the frequency converter:
Voltage
200 - 240 V 1.1 - 3.7 kW 5.5 - 45 kW
380 - 480 V 1.1 - 7.5 kW 11 - 90 kW 110 -200 kW 250 - 450 kW
525 - 600 V 1.1 - 7.5 kW 110 - 250 kW 315 - 560 kW
4 min. 15 min. 20 min. 30 min. 40 min.
Be aware that there may be high voltage on the DC link even when the LEDs are turned off.
Minimum Waiting Time
Equipment containing electrical components may not be disposed of together with domestic
waste.
It must be separately collected with electrical and electronic waste according to local and currently
valid legislation.
2.2. CE labelling
2.2.1. CE Conformity and Labelling
What is CE Conformity and Labelling?
The purpose of CE labelling is to avoid technical trade obstacles within EFTA and the EU. The EU has introduced the CE label as a simple way of showing
whether a product complies with the relevant EU directives. The CE label says nothing about the specifications or quality of the product. Frequency
converters are regulated by three EU directives:
The machinery directive (98/37/EEC)
All machines with critical moving parts are covered by the machinery directive of January 1, 1995. Since a frequency converter is largely electrical, it does
not fall under the machinery directive. However, if a frequency converter is supplied for use in a machine, we provide information on safety aspects
relating to the frequency converter. We do this by means of a manufacturer's declaration.
The low-voltage directive (73/23/EEC)
Frequency converters must be CE labelled in accordance with the low-voltage directive of January 1, 1997. The directive applies to all electrical equipment
and appliances used in the 50 - 1000 V AC and the 75 - 1500 V DC voltage ranges. Danfoss CE-labels in accordance with the directive and issues a
declaration of conformity upon request.
The EMC directive (89/336/EEC)
EMC is short for electromagnetic compatibility. The presence of electromagnetic compatibility means that the mutual interference between different
components/appliances does not affect the way the appliances work.
The EMC directive came into effect January 1, 1996. Danfoss CE-labels in accordance with the directive and issues a declaration of conformity upon
request. To carry out EMC-correct installation, see the instructions in this Design Guide. In addition, we specify which standards our products comply
with. We offer the filters presented in the specifications and provide other types of assistance to ensure the optimum EMC result.
The frequency converter is most often used by professionals of the trade as a complex component forming part of a larger appliance, system or installation.
It must be noted that the responsibility for the final EMC properties of the appliance, system or installation rests with the installer.
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VLT® HVAC Drive Design Guide 2. Introduction to VLT HVAC Drive
2.2.2. What Is Covered
The EU "
Guidelines on the Application of Council Directive 89/336/EEC
coverage and CE labelling.
" outline three typical situations of using a frequency converter. See below for EMC
1. The frequency converter is sold directly to the end-consumer. The frequency converter is for example sold to a DIY market. The end-consumer
is a layman. He installs the frequency converter himself for use with a hobby machine, a kitchen appliance, etc. For such applications, the
frequency converter must be CE labelled in accordance with the EMC directive.
2. The frequency converter is sold for installation in a plant. The plant is built up by professionals of the trade. It could be a production plant or a
heating/ventilation plant designed and installed by professionals of the trade. Neither the frequency converter nor the finished plant has to be
CE labelled under the EMC directive. However, the unit must comply with the basic EMC requirements of the directive. This is ensured by using
components, appliances, and systems that are CE labelled under the EMC directive.
3. The frequency converter is sold as part of a complete system. The system is being marketed as complete and could e.g. be an air-conditioning
system. The complete system must be CE labelled in accordance with the EMC directive. The manufacturer can ensure CE labelling under the
EMC directive either by using CE labelled components or by testing the EMC of the system. If he chooses to use only CE labelled components,
he does not have to test the entire system.
2.2.3. Danfoss Frequency Converter and CE Labelling
CE labelling is a positive feature when used for its original purpose, i.e. to facilitate trade within the EU and EFTA.
However, CE labelling may cover many different specifications. Thus, you have to check what a given CE label specifically covers.
The covered specifications can be very different and a CE label may therefore give the installer a false feeling of security when using a frequency converter
as a component in a system or an appliance.
Danfoss CE labels the frequency converters in accordance with the low-voltage directive. This means that if the frequency converter is installed correctly,
we guarantee compliance with the low-voltage directive. Danfoss issues a declaration of conformity that confirms our CE labelling in accordance with the
low-voltage directive.
2
The CE label also applies to the EMC directive provided that the instructions for EMC-correct installation and filtering are followed. On this basis, a
declaration of conformity in accordance with the EMC directive is issued.
The Design Guide offers detailed instructions for installation to ensure EMC-correct installation. Furthermore, Danfoss specifies which our different prod-
ucts comply with.
Danfoss gladly provides other types of assistance that can help you obtain the best EMC result.
2.2.4. Compliance with EMC Directive 89/336/EEC
As mentioned, the frequency converter is mostly used by professionals of the trade as a complex component forming part of a larger appliance, system,
or installation. It must be noted that the responsibility for the final EMC properties of the appliance, system or installation rests with the installer. As an
aid to the installer, Danfoss has prepared EMC installation guidelines for the Power Drive system. The standards and test levels stated for Power Drive
systems are complied with, provided that the EMC-correct instructions for installation are followed, see the section
EMC Immunity
.
2.3. Air humidity
2.3.1. Air Humidity
The frequency converter has been designed to meet the IEC/EN 60068-2-3 standard, EN 50178 pkt. 9.4.2.2 at 50°C.
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2. Introduction to VLT HVAC Drive VLT® HVAC Drive Design Guide
2.4. Aggressive Environments
A frequency converter contains a large number of mechanical and electronic components. All are to some extent vulnerable to environmental effects.
2
The frequency converter should not be installed in environments with airborne liquids, particles, or gases capable of affecting and
damaging the electronic components. Failure to take the necessary protective measures increases the risk of stoppages, thus reducing
the life of the frequency converter.
Liquids can be carried through the air and condense in the frequency converter and may cause corrosion of components and metal parts. Steam, oil, and
salt water may cause corrosion of components and metal parts. In such environments, use equipment with enclosure rating IP 54/55. As an extra
protection, coated printet circuit boards can be orded as an option.
Particles such as dust may cause mechanical, electrical, or thermal failure in the frequency converter. A typical indicator of excessive levels of
Airborne
airborne particles is dust particles around the frequency converter fan. In very dusty environments, use equipment with enclosure rating IP 54/55 or a
cabinet for IP 00/IP 20/TYPE 1 equipment.
In environments with high temperatures and humidity,
on the frequency converter components.
Such chemical reactions will rapidly affect and damage the electronic components. In such environments, mount the equipment in a cabinet with fresh
air ventilation, keeping aggressive gases away from the frequency converter.
An extra protection in such areas is a coating of the printed circuit boards, which can be ordered as an option.
NB!
Mounting frequency converters in aggressive environments increases the risk of stoppages and considerably reduces the life of the
converter.
corrosive gases such as sulphur, nitrogen, and chlorine compounds will cause chemical processes
Before installing the frequency converter, check the ambient air for liquids, particles, and gases. This is done by observing existing installations in this
environment. Typical indicators of harmful airborne liquids are water or oil on metal parts, or corrosion of metal parts.
Excessive dust particle levels are often found on installation cabinets and existing electrical installations. One indicator of aggressive airborne gases is
blackening of copper rails and cable ends on existing installations.
2.5. Vibration and shock
The frequency converter has been tested according to the procedure based on the shown standards:
The frequency converter complies with requirements that exist for units mounted on the walls and floors of production premises, as well as in panels
bolted to walls or floors.
IEC/EN 60068-2-6: Vibration (sinusoidal) - 1970
IEC/EN 60068-2-64: Vibration, broad-band random
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VLT® HVAC Drive Design Guide 2. Introduction to VLT HVAC Drive
2.6. Advantages
2.6.1. Why use a frequency converter for controlling fans and pumps?
A frequency converter takes advantage of the fact that centrifugal fans and pumps follow the laws of proportionality for such fans and pumps. For further
information see the text
The Laws of Proportionality
.
2.6.2. The clear advantage - energy savings
The very clear advantage of using a frequency converter for controlling the speed of fans or pumps lies in the electricity savings.
When comparing with alternative control systems and technologies, a frequency converter is the optimum energy control system for controlling fan and
pump systems.
Illustration 2.1: The graph is showing fan curves (A, B and C) for re-
duced fan volumes.
2
Illustration 2.2: When using a frequency converter to reduce fan ca-
pacity to 60% - more than 50% energy savings may be obtained in
typical applications.
2.6.3. Example of energy savings
As can be seen from the figure (the laws of proportionality), the flow is controlled by changing the rpm. By reducing the speed only 20% from the rated
speed, the flow is also reduced by 20%. This is because the flow is directly proportional to the rpm. The consumption of electricity, however, is reduced
by 50%.
If the system in question only needs to be able to supply a flow that corresponds to 100% a few days in a year, while the average is below 80% of the
rated flow for the remainder of the year, the amount of energy saved is even more than 50%.
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2. Introduction to VLT HVAC Drive VLT® HVAC Drive Design Guide
The laws of proportionality
The figure below describes the dependence of flow, pressure and power consumption on rpm.
Q = Flow P = Power
Q1 = Rated flow P1 = Rated power
Q
= Reduced flow P2 = Reduced power
2
H = Pressure n = Speed regulation
H1 = Rated pressure n1 = Rated speed
H
= Reduced pressure n2 = Reduced speed
2
2.6.4. Comparison of energy savings
The Danfoss frequency converter solution offers major savings compared
with traditional energy saving solutions. This is because the frequency
converter is able to control fan speed according to thermal load on the
system and the fact that the frequency converter has a build-in facility
that enables the frequency converter to function as a Building Manage-
ment System, BMS.
Flow
:
Pressure
Power
Q
Q
:
:
n
1
2
P
P
1
=
n
2
H
H
1
2
n
(
2
1
(
)
n
2
n
3
1
)
n
2
1
=
2
=
The graph below illustrates typical energy savings obtainable with 3 well-
known solutions when fan volume is reduced to i.e. 60%.
As the graph shows, more than 50% energy savings can be achieved in
typical applications.
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Illustration 2.3: The three common energy saving systems.
VLT® HVAC Drive Design Guide 2. Introduction to VLT HVAC Drive
2
Illustration 2.4: Discharge dampers reduce power consumption somewhat. Inlet Guide Vans offer a 40% reduction but are expensive to install. The
Danfossfrequency converter solution reduces energy consumption with more than 50% and is easy to install.
2.6.5. Example with varying flow over 1 year
The example below is calculated on the basis of pump characteristics ob-
tained from a pump datasheet.
The result obtained shows energy savings in excess of 50% at the given
flow distribution over a year. The pay back period depends on the price
per kwh and price of frequency converter. In this example it is less than
a year when compared with valves and constant speed.
Energy savings
P
shaft=Pshaft output
Flow distribution over 1 year
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2. Introduction to VLT HVAC Drive VLT® HVAC Drive Design Guide
m3/h
Distribution Valve regulation Frequency converter control
% Hours Power Consumption Power Consumption
A1 - B
350 5 438 42,5 18.615 42,5 18.615
300 15 1314 38,5 50.589 29,0 38.106
250 20 1752 35,0 61.320 18,5 32.412
200 20 1752 31,5 55.188 11,5 20.148
150 20 1752 28,0 49.056 6,5 11.388
100 20 1752 23,0 40.296 3,5 6.132
Σ 100 8760 275.064 26.801
1
kWh A1 - C
1
2.6.6. Better control
If a frequency converter is used for controlling the flow or pressure of a system, improved control is obtained.
A frequency converter can vary the speed of the fan or pump, thereby obtaining variable control of flow and pressure.
Furthermore, a frequency converter can quickly adapt the speed of the fan or pump to new flow or pressure conditions in the system.
Simple control of process (Flow, Level or Pressure) utilizing the built in PID control.
kWh
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2.6.7. Cos φ compensation
Generally speaking, a frequency converter with a cos φ of 1 provides power factor correction for the cos φ of the motor, which means that there is no
need to make allowance for the cos φ of the motor when sizing the power factor correction unit.
2.6.8. Star/delta starter or soft-starter not required
When larger motors are started, it is necessary in many countries to use equipment that limits the start-up current. In more traditional systems, a star/
delta starter or soft-starter is widely used. Such motor starters are not required if a frequency converter is used.
As illustrated in the figure below, a frequency converter does not consume more than rated current.
1 = VLT HVAC Drive
2 = Star/delta starter
3 = Soft-starter
4 = Start directly on mains
2.6.9. Using a frequency converter saves money
The example on the following page shows that a lot of equipment is not required when a frequency converter is used. It is possible to calculate the cost
of installing the two different systems. In the example on the following page, the two systems can be established at roughly the same price.
2
2.6.10. Without a frequency converter
The figure shows a fan system made in the traditional way.
D.D.C. = Direct Digital Control E.M.S. = Energy Management system
V.A.V. = Variable Air Volume
Sensor P = Pressure Sensor T = Temperature
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2.6.11. With a frequency converter
The figure shows a fan system controlled by frequency converters.
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VLT® HVAC Drive Design Guide 2. Introduction to VLT HVAC Drive
2.6.12. Application examples
The next few pages give typical examples of applications within HVAC.
If you would like to receive further information about a given application, please ask your Danfoss supplier for an information sheet that gives a full
description of the application.
Variable Air Volume
Ask for The Drive to...Improving Variable Air Volume Ventilation Systems MN.60.A1.02
Constant Air Volume
Ask for The Drive to...Improving Constant Air Volume Ventilation Systems MN.60.B1.02
Cooling Tower Fan
Ask for The Drive to...Improving fan control on cooling towers MN.60.C1.02
Condenser pumps
Ask for The Drive to...Improving condenser water pumping systems MN.60.F1.02
Primary pumps
Ask for The Drive to...Improve your primary pumping in primay/secondary pumping systems MN.60.D1.02
Secondary pumps
Ask for The Drive to...Improve your secondary pumping in primay/secondary pumping systems MN.60.E1.02
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2. Introduction to VLT HVAC Drive VLT® HVAC Drive Design Guide
2.6.13. Variable Air Volume
VAV or Variable Air Volume systems, are used to control both the ventilation and temperature to satisfy the requirements of a building. Central VAV
systems are considered to be the most energy efficient method to air condition buildings. By designing central systems instead of distributed systems, a
greater efficiency can be obtained.
The efficiency comes from utilizing larger fans and larger chillers which have much higher efficiencies than small motors and distributed air-cooled chillers.
Savings are also seen from the decreased maintenance requirements.
2.6.14. The VLT solution
While dampers and IGVs work to maintain a constant pressure in the ductwork, a frequency converter solution saves much more energy and reduces
the complexity of the installation. Instead of creating an artificial pressure drop or causing a decrease in fan efficiency, the frequency converter decreases
the speed of the fan to provide the flow and pressure required by the system.
Centrifugal devices such as fans behave according to the centrifugal laws. This means the fans decrease the pressure and flow they produce as their
speed is reduced. Their power consumption is thereby significantly reduced.
The return fan is frequently controlled to maintain a fixed difference in airflow between the supply and return. The advanced PID controller of the HVAC
frequency converter can be used to eliminate the need for additional controllers.
Pressure
Cooling coil
D1
D2
Heating coil
Filter
signal
Supply fan
3
Flow
Pressure
transmitter
VAV boxes
T
Return fan
D3
Flow
3
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2.6.15. Constant Air Volume
CAV, or Constant Air Volume systems are central ventilation systems usually used to supply large common zones with the minimum amounts of fresh
tempered air. They preceded VAV systems and therefore are found in older multi-zoned commercial buildings as well. These systems preheat amounts
of fresh air utilizing Air Handling Units (AHUs) with a heating coil, and many are also used to air condition buildings and have a cooling coil. Fan coil units
are frequently used to assist in the heating and cooling requirements in the individual zones.
2.6.16. The VLT solution
2
With a frequency converter, significant energy savings can be obtained while maintaining decent control of the building. Temperature sensors or CO
sensors can be used as feedback signals to frequency converters. Whether controlling temperature, air quality, or both, a CAV system can be controlled
to operate based on actual building conditions. As the number of people in the controlled area decreases, the need for fresh air decreases. The CO
sensor detects lower levels and decreases the supply fans speed. The return fan modulates to maintain a static pressure setpoint or fixed difference
between the supply and return air flows.
With temperature control, especially used in air conditioning systems, as the outside temperature varies as well as the number of people in the controlled
zone changes, different cooling requirements exist. As the temperature decreases below the set-point, the supply fan can decrease its speed. The return
fan modulates to maintain a static pressure set-point. By decreasing the air flow, energy used to heat or cool the fresh air is also reduced, adding further
savings.
Several features of the Danfoss HVAC dedicated frequency converter can be utilized to improve the performance of your CAV system. One concern of
controlling a ventilation system is poor air quality. The programmable minimum frequency can be set to maintain a minimum amount of supply air
regardless of the feedback or reference signal. The frequency converter also includes a 3-zone, 3 setpoint PID controller which allows monitoring both
temperature and air quality. Even if the temperature requirement is satisfied, the frequency converter will maintain enough supply air to satisfy the air
quality sensor. The controller is capable of monitoring and comparing two feedback signals to control the return fan by maintaining a fixed differential
air flow between the supply and return ducts as well.
Temperature
Cooling coil
D1
Heating coil
Filter
signal
Supply fan
Temperature
transmitter
2
2
D2
D3
Pressure
signal
Return fan
Pressure
transmitter
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2.6.17. Cooling Tower Fan
Cooling Tower Fans are used to cool condenser water in water cooled chiller systems. Water cooled chillers provide the most efficient means of creating
chilled water. They are as much as 20% more efficient than air cooled chillers. Depending on climate, cooling towers are often the most energy efficient
method of cooling the condenser water from chillers.
They cool the condenser water by evaporation.
The condenser water is sprayed into the cooling tower onto the cooling towers “fill” to increase its surface area. The tower fan blows air through the fill
and sprayed water to aid in the evaporation. Evaporation removes energy from the water dropping its temperature. The cooled water collects in the
cooling towers basin where it is pumped back into the chillers condenser and the cycle is repeated.
2.6.18. The VLT solution
With a frequency converter, the cooling towers fans can be controlled to the required speed to maintain the condenser water temperature. The frequency
converters can also be used to turn the fan on and off as needed.
Several features of the Danfoss HVAC dedicated frequency converter, the HVAC frequency converter can be utilized to improve the performance of your
cooling tower fans application. As the cooling tower fans drop below a certain speed, the effect the fan has on cooling the water becomes small. Also,
when utilizing a gear-box to frequency control the tower fan, a minimum speed of 40-50% may be required.
The customer programmable minimum frequency setting is available to maintain this minimum frequency even as the feedback or speed reference calls
for lower speeds.
Also as a standard feature, you can program the frequency converter to enter a “sleep” mode and stop the fan until a higher speed is required. Additionally,
some cooling tower fans have undesireable frequencies that may cause vibrations. These frequencies can easily be avoided by programming the bypass
frequency ranges in the frequency converter.
Water Inlet
Temperature
Sensor
BASIN
Water Outlet
Conderser
Water pump
CHILLER
Supply
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2.6.19. Condenser pumps
Condenser Water pumps are primarily used to circulate water through the condenser section of water cooled chillers and their associated cooling tower.
The condenser water absorbs the heat from the chiller's condenser section and releases it into the atmosphere in the cooling tower. These systems are
used to provide the most efficient means of creating chilled water, they are as much as 20% more efficient than air cooled chillers.
2.6.20. The VLT solution
Frequency converters can be added to condenser water pumps instead of balancing the pumps with a throttling valve or trimming the pump impeller.
Using a frequency converter instead of a throttling valve simply saves the energy that would have been absorbed by the valve. This can amount to savings
of 15-20% or more. Trimming the pump impeller is irreversible, thus if the conditions change and higher flow is required the impeller must be replaced.
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2. Introduction to VLT HVAC Drive VLT® HVAC Drive Design Guide
2.6.21. Primary pumps
Primary pumps in a primary/secondary pumping system can be used to maintain a constant flow through devices that encounter operation or control
difficulties when exposed to variable flow. The primary/ secondary pumping technique decouples the “primary” production loop from the “secondary”
distribution loop. This allows devices such as chillers to obtain constant design flow and operate properly while allowing the rest of the system to vary in
flow.
As the evaporator flow rate decreases in a chiller, the chilled water begins to become over-chilled. As this happens, the chiller attempts to decrease its
cooling capacity. If the flow rate drops far enough, or too quickly, the chiller cannot shed its load sufficiently and the chiller’s low evaporator tempera-
ture safety trips the chiller requiring a manual reset. This situation is common in large installations especially when two or more chillers in parallel are
installed if primary/ secondary pumping is not utilized.
2.6.22. The VLT solution
Depending on the size of the system and the size of the primary loop, the energy consumption of the primary loop can become substantial.
A frequency converter can be added to the primary system, to replace the throttling valve and/or trimming of the impellers, leading to reduced operating
expenses. Two control methods are common:
The first method uses a flow meter. Because the desired flow rate is known and is constant, a flow meter installed at the discharge of each chiller, can
be used to control the pump directly. Using the built-in PID controller, the frequency converter will always maintain the appropriate flow rate, even
compensating for the changing resistance in the primary piping loop as chillers and their pumps are staged on and off.
The other method is local speed determination. The operator simply decreases the output frequency until the design flow rate is achieved.
Using a frequency converter to decrease the pump speed is very similar to trimming the pump impeller, except it doesn’t require any labor and the pump
efficiency remains higher. The balancing contractor simply decreases the speed of the pump until the proper flow rate is achieved and leaves the speed
fixed. The pump will operate at this speed any time the chiller is staged on. Because the primary loop doesn’t have control valves or other devices that
can cause the system curve to change and the variance due to staging pumps and chillers on and off is usually small, this fixed speed will remain
appropriate. In the event the flow rate needs to be increased later in the systems life, the frequency converter can simply increase the pump speed
instead of requiring a new pump impeller.
Flowmeter
F
CHILLER
Flowmeter
F
CHILLER
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2.6.23. Secondary pumps
Secondary pumps in a primary/secondary chilled water pumping system are used to distribute the chilled water to the loads from the primary production
loop. The primary/secondary pumping system is used to hydronically de-couple one piping loop from another. In this case. The primary pump is used to
maintain a constant flow through the chillers while allowing the secondary pumps to vary in flow, increase control and save energy.
If the primary/secondary design concept is not used and a variable volume system is designed, when the flow rate drops far enough or too quickly, the
chiller cannot shed its load properly. The chiller’s low evaporator temperature safety then trips the chiller requiring a manual reset. This situation is
common in large installations especially when two or more chillers in parallel are installed.
2.6.24. The VLT solution
While the primary-secondary system with two-way valves improves energy savings and eases system control problems, the true energy savings and
control potential is realized by adding frequency converters.
With the proper sensor location, the addition of frequency converters allows the pumps to vary their speed to follow the system curve instead of the
pump curve.
This results in the elimination of wasted energy and eliminates most of the over-pressurization, two-way valves can be subjected too.
As the monitored loads are reached, the two-way valves close down. This increases the differential pressure measured across the load and two-way
va lv e. A s t his di ffe re ntia l p res su re sta rt s to r is e , the p um p is slowed to maintain the control head also called setpoint value. This set-point value is calculated
by summing the pressure drop of the load and two way valve together under design conditions.
2
NB!
Please note that when running multiple pumps in parallel, they must run at the same speed to maximize energy savings, either with
individual dedicated drives or one frequency converter running multiple pumps in parallel.
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2. Introduction to VLT HVAC Drive VLT® HVAC Drive Design Guide
2.7. VLT HVAC Drive Controls
2.7.1. Control Principle
2
A frequency converter rectifies AC voltage from mains into DC voltage, after which this DC voltage is converted into a AC current with a variable amplitude
and frequency.
The motor is supplied with variable voltage / current and frequency, which enables infinitely variable speed control of three-phased, standard AC motors.
2.7.2. Control Structure
Control structure in open loop and closed loop configurations:
In the configuration shown in the illustration above, par. 1-00 is set to
received and fed through the ramp limitation and speed limitation before being sent to the motor control. The output of the motor control is then limited
by the maximum frequency limit.
Closed loop
Select
parameters are located in par. group 20-**.
[3] in par. 1-00 to use the PID controller for closed loop control of e.g. flow, level or pressure in the controlled application. The PID
Open loop
[0]. The resulting reference from the reference handling system is
2.7.3. Local (Hand On) and Remote (Auto On) Control
The frequency converter can be operated manually via the local control panel (LCP) or remotely via analog and digital inputs and serial bus.
If allowed in par. 0-40, 0-41, 0-42, and 0-43, it is possible to start and stop the frequency converter via the LCP using the [Hand ON] and [Off] keys.
Alarms can be reset via the [RESET] key. After pressing the [Hand On] key, the frequency converter goes into Hand Mode and follows (as default) the
Local reference set by using the LCP arrow keys.
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After pressing the [Auto On] key, the frequency converter goes into Auto
mode and follows (as default) the Remote reference. In this mode, it is
possible to control the frequency converter via the digital inputs and var-
ious serial interfaces (RS-485, USB, or an optional fieldbus). See more
about starting, stopping, changing ramps and parameter set-ups etc. in
par. group 5-1* (digital inputs) or par. group 8-5* (serial communica-
tion).
130BP046.1
Active Reference and Configuration Mode
The active reference can be either the local reference or the remote ref-
erence.
2
In par. 3-13
lected by selecting
To permanently select the remote reference select
lecting
on which mode is active. (Hand Mode or Auto Mode).
Hand Off
Auto
LCP Keys
Hand Linked to Hand / Auto Local
Hand -> Off Linked to Hand / Auto Local
Auto Linked to Hand / Auto Remote
Auto -> Off Linked to Hand / Auto Remote
All keys Local Local
All keys Remote Remote
The table shows under which conditions either the Local reference or the Remote reference is active. One of them is always active, but both can not be
active at the same time.
NB!
Local Ref. will be restored at power-down.
Reference Site
Par. 3-13
Reference Site
Linked to Hand/Auto
the local reference can be permanently se-
Local
[2].
Remote
[0] (default) the reference site will depend
Active Reference
[1]. By se-
Par. 1-00
is active (see table above for the conditions).
Reference Handling - Local Reference
Configuration Mode
determines what kind of application control principle (i.e. Open Loop or Closed loop) is used when the Remote reference
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2.8. PID
2.8.1. Closed Loop (PID) Controller
2
The frequency converter’s Closed Loop Controller allows the frequency converter to become an integral part of the controlled system. The frequency
converter receives a feedback signal from a sensor in the system. It then compares this feedback to a setpoint reference value and determines the error,
if any, between these two signals. It then adjusts the speed of the motor to correct this error.
For example, consider a ventilation system where the speed of the supply fan is to be controlled so that the static pressure in the duct is constant. The
desired static pressure value is supplied to the frequency converter as the setpoint reference. A static pressure sensor measures the actual static pressure
in the duct and supplies this to the frequency converter as a feedback signal. If the feedback signal is greater than the setpoint reference, the frequency
converter will slow down to reduce the pressure. In a similar way, if the duct pressure is lower than the setpoint reference, the frequency converter will
automatically speed up to increase the pressure provided by the fan.
NB!
While the default values for the frequency converter’s Closed Loop Controller will often provide satisfactory performance, the control
of the system can often be optimized by adjusting some of the Closed Loop Controller’s parameters.
The figure is a block diagram of the frequency converter’s Closed Loop Controller. The details of the Reference Handling block and Feedback Handling
block are described in their respective sections below.
The following parameters are relevant for a simple PID control application:
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