Danfoss VLT series Guide

Contents
1. How to Read this Design Guide
5
Copyright, Limitation of Liability and Revision Rights 5
Approvals 6
Symbols 6
Abbreviations 7
Definitions 7
2. Introduction to the VLT HVAC Drive 13
Disposal Instructions 14
CE labeling 16
Air humidity 18
Aggressive Environments 18
Vibration and shock 19
VLT HVAC Controls 33
PID 35
General aspects of EMC 47
Galvanic isolation (PELV) 50
Ground leakage current 51
Control with brake function 51
Mechanical brake control 53
Extreme running conditions 53
3. VLT HVAC Selection 55
Specifications 55
Efficiency 66
Special Conditions 68
Purpose of derating 68
Automatic adaptations to ensure performance 71
Options and Accessories 74
Analog I/O option MCB 109 80
4. How to Order 85
Ordering form 85
Type Code String 86
Ordering Numbers 87
5. How to Install 93
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Mechanical Installation 93
Accessory Bag 93
Electrical Installation 95
Removal of Knockouts for Extra Cables 95
Access to Control Terminals 103
Electrical Installation, Control Terminals 104
Final Set-Up and Test 108
Final Set-Up and Test 108
Additional Connections 110
Installation of misc. connections 114
Safety 117
EMC-correct Installation 118
AC Line Supply Interference/Harmonics 122
Residual Current Device 122
6. Application Examples 125
Start/Stop 125
Pulse Start/Stop 125
Potentiometer Reference 126
Automatic Motor Adaptation (AMA) 126
Smart Logic Control 127
Smart Logic Control Programming 127
SLC Application Example 127
BASIC Cascade Controller 129
Pump Staging with Lead Pump Alternation 130
System Status and Operation 131
Fixed Variable Speed Pump Wiring Diagram 132
Lead Pump Alternation Wiring Diagram 132
Cascade Controller Wiring Diagram 133
Start/Stop conditions 133
7. RS-485 Installation and Set-up 135
RS-485 Installation and Set-up 135
FC Protocol Overview 138
Network Configuration 139
FC Protocol Message Framing Structure 139
Examples 145
Modbus RTU Overview 146
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Modbus RTU Message Framing Structure 147
How to Access Parameters 152
Examples 153
Danfoss FC Control Profile 160
8. Troubleshooting 167
Alarms and warnings 167
Index
173
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1. How to Read this Design Guide VLT
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1. How to Read this Design Guide
1.1.1. Copyright, Limitation of Liability and Revision Rights
This publication contains information proprietary to Danfoss A/S. By accepting and using this
manual, the user agrees that the information contained herein will be used solely for operating
equipment from Danfoss A/S or equipment from other vendors, provided that such equipment is
intended for communication with Danfoss equipment over a serial communication link. This pub-
lication is protected under the copyright laws of Denmark and most other countries.
Danfoss A/S does not guarantee 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 A/S has tested and reviewed the documentation within this manual,
Danfoss A/S 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 A/S be liable for direct, indirect, special, incidental or consequential
damages arising from the use or the inability to use information contained in this manual, even if
advised of the possibility of such damages. In particular, Danfoss A/S is not responsible for any
costs, including, but not limited to, those incurred as a result of lost profits or revenue, loss of or
damages to equipment, loss of computer programs, loss of data, the costs to substitute these, or
any claims by third parties.
Danfoss A/S 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.
1.1.2. AvailableLiterature
Available literature for VLT HVAC Drive
-Instruction Manual MG.11.Ax.yy provides the necessary information for getting the drive
up and running.
-Design Guide MG.11.Bx.yy provides all the technical information about the drive and
customer design and applications.
-Programming Guide MG.11.Cx.yy provides information on how to program and includes
complete parameter descriptions.
-Mounting Instruction, Analog I/O Option MCB109, MI.38.Bx.yy
-VLT
®
6000 HVAC Application Booklet, MN.60.Ix.yy
-Instruction Manual VLT
®
HVAC Drive BACnet, MG.11.Dx.yy
-Instruction Manual VLT
®
HVAC Drive Profibus, MG.33.Cx.yy.
-Instruction Manual VLT
®
HVAC Drive Device Net, MG.33.Dx.yy
-Instruction Manual VLT
®
HVAC Drive LonWorks, MG.11.Ex.yy
-Instruction Manual VLT
®
HVAC Drive Metasys, MG.11.Gx.yy
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x = Revision number
yy = Language code
Danfoss Drives technical literature is also available online at
www.danfoss.com/BusinessAreas/
DrivesSolutions/Documentations/Technical+Documentation
.
1.1.3. Approvals
1.1.4. Symbols
Symbols used in this guide.
NOTE
Indicates something to be noted by the reader.
Indicates a general warning.
Indicates a high-voltage warning.
*Indicates default setting
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1.1.5. Abbreviations
Alternating current AC
American wire gauge AWG
Ampere/AMP A
Automatic Motor Adaptation AMA
Current limit ILIM
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 LCP
Meter m
Millihenry Inductance mH
Milliampere mA
Millisecond ms
Minute min
Motion Control Tool MCT
Nanofarad nF
Newton Meters Nm
Nominal motor current IM,N
Nominal motor frequency fM,N
Nominal motor power PM,N
Nominal motor voltage UM,N
Parameter par.
Protective Extra Low Voltage PELV
Printed Circuit Board PCB
Rated Inverter Output Current IINV
Revolutions Per Minute RPM
Second s
Torque limit TLIM
Volt V
1.1.6. Definitions
Drive:
I
VLT,MAX
The maximum output current.
I
VLT,N
The rated output current supplied by the adjustable frequency drive.
U
VLT, MAX
The maximum output voltage.
Input:
Control command
You can start and stop the connected motor using
the LCP and the digital inputs.
Functions are divided into two groups.
Functions in group 1 have higher priority than
functions in group 2.
Group 1 Reset, Coasting stop, Reset and Coasting
stop, Quick stop, DC braking, Stop and the
"Off" key.
Group 2 Start, Pulse start, Reversing, Start reversing,
Jog and Freeze output
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Motor:
f
JOG
The motor frequency when the jog function is activated (via digital terminals).
f
M
The motor frequency.
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).
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Break-away torque
η
VLT
The efficiency of the adjustable frequency drive 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.
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,
20 mA) 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 0 V, 0 mA, 4 mA)
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 adjustable frequency drive.
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There are two types of analog inputs:
Current input, 0-20 mA and 4-20 mA
Voltage input, 0-10 V DC.
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 braking energy generated in regenerative
braking. This regenerative braking energy increases the intermediate circuit voltage, while a brake
chopper ensures that the energy 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 adjustable frequency drive.
Digital Outputs
The drive features two solid state outputs that can supply a 24 V DC (max. 40 mA) signal.
DSP
Digital Signal Processor.
Relay Outputs:
The adjustable frequency drive features two programmable relay outputs.
ETR
Electronic Thermal Relay is a thermal load calculation based on present load and time. Its purpose
is to estimate the motor temperature.
GLCP:
Graphical Local Control Panel (LCP102)
Initializing
If initializing is carried out (par. 14-22), the programmable parameters of the adjustable frequency
drive 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 a periodic or non-periodic duty.
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LCP
The Local Control Panel (LCP) makes up a complete interface for control and programming of the
adjustable frequency drive. The control panel is detachable and can be installed up to 9.8 ft (3
meters) from the adjustable frequency drive, 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 0.00079≡
in.
2
(0.5067 mm
2
).
msb
Most significant bit.
NLCP
Numerical Local Control Panel LCP101
Online/Offline Parameters
Changes to online parameters are activated immediately after the data value is changed. Changes
to offline 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 out-
put 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 while another set-up is active.
SFAVM
Switching pattern called Stator Flux-oriented Asynchronous Vector Modulation (par. 14-00).
Slip Compensation
The adjustable frequency drive compensates for the motor slip by giving the frequency a supple-
ment that follows the measured motor load, thus keeping the motor speed almost constant.
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.
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Thermistor:
A temperature-dependent resistor placed where the temperature is to be monitored (adjustable
frequency drive or motor).
Trip
A state entered in fault situations, such as when the adjustable frequency drive is subject to an
overtemperature, or when the adjustable frequency drive is protecting the motor, process or
mechanism. Restart is prevented until the cause of the fault has rectified and the trip state is
cancelled by activating reset, or, in some cases, by programming an automatic reset. Trip may
not be used as a personal safety measure.
Trip-Locked
A state entered in fault situations when the adjustable frequency drive is protecting itself and
requiring physical intervention, such as when the adjustable frequency drive is subject to a short
circuit on the output. A locked trip can only be cancelled by cutting off line power, removing the
cause of the fault and reconnecting the adjustable frequency drive. Restart is prevented until the
trip state is cancelled by activating reset or, in some cases, by being programmed to reset auto-
matically. The trip-lock function may not be used as a personal safety measure.
VT Characteristics
Variable torque characteristics used for pumps and fans.
VVCplus
Compared with standard voltage/frequency ratio control, voltage vector control (VVC
plus
) improves
the dynamics and the stability, both when the speed reference is changed and in relation to the
load torque.
60° AVM
Switching pattern called 60°Asynchronous Vector Modulation (par. 14-00).
1.1.7. Power Factor
The power factor is the relation between I
1
and I
RMS
.
Power factor =
3× U × I
1× COS ϕ
3× U × IRMS
The power factor for 3-phase control:
=
I
1×
cos ϕ1
IRMS
=
I
1
IRMS
since cos
ϕ1=1
The power factor indicates to which extent the
adjustable frequency drive imposes a load on
the line supply.
The lower the power factor, the higher the
I
RMS
for the same kW performance.
IRMS = I
2
1+
I
2
5+
I
2
7+..+
I
2
n
In addition, a high power factor indicates that the different harmonic currents are low.
The adjustable frequency drive's built-in DC coils produce a high power factor, which minimizes
the imposed load on the line power supply.
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2. Introduction to the VLT HVAC Drive
2.1. Safety
2.1.1. Safety note
The voltage of the adjustable frequency drive is dangerous whenever connected to
line power. Incorrect installation of the motor, adjustable frequency drive or serial
communication bus 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 followed.
Safety Regulations
1. The adjustable frequency drive must be disconnected from line power if repair work is to be
carried out. Make sure that the line supply has been disconnected and that the necessary time
has passed before removing motor and line plugs.
2. The [STOP/RESET] key on the control panel of the adjustable frequency drive does not dis-
connect the equipment from line power and is thus not to be used as a safety switch.
3. Correct protective grounding 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 ground leakage currents are higher than 3.5 mA.
5. Protection against motor overload is set by
par. 1-90 Motor Thermal Protection . If this function
is desired, set par. 1-90 to data value [ETR trip] (default value) or data value [ETR warning]. Note:
The function is initialized 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 line supply while the adjustable frequency drive is
connected to line power. Make sure that the line supply has been disconnected and that the
necessary time has passed before removing motor and line plugs.
7. Please note that the adjustable frequency drive 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.
Make sure that all voltage inputs have been disconnected and that the necessary time has passed
before commencing repair work.
Installation at High Altitudes
At altitudes higher than 6,600 feet [2 km], please contact Danfoss Drives 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 adjustable frequency drive is connected to line power. 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 adjustable fre-
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quency drive, or if a temporary overload or a fault in the supply line or the motor connection
ceases.
Warning:
Touching the electrical parts may be fatal - even after the equipment has been dis-
connected from line power.
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 backup.
Refer to
VLT® HVAC Drive Instruction Manual MG.11.Ax.yy for further safety guidelines.
2.1.2. Caution
Caution
The adjustable frequency drive DC link capacitors remain charged after power has been dis-
connected. To avoid the risk of electrical shock, disconnect the adjustable frequency drive
from line power before performing maintenance procedures. Wait at least as long as follows
before servicing the adjustable frequency drive:
Voltage Min. Waiting Time
4 min. 15 min.
200 - 240 V 1.5-5 hp [1.1-3.7 kW] 7.5-60 hp [5.5-45 kW]
380 - 480 V 1.5-10 hp [1.1-7.5 kW] 15-125 hp [11-90 kW]
525 - 600 V 1.5-10 hp [1.1-7.5 kW]
Be aware that there may be high voltage on the DC link even when the LEDs are turned off.
2.1.3. Disposal Instructions
Equipment containing electrical components may not be disposed of
together with domestic waste.
It must be collected separately as electrical and electronic waste in
accordance with local and currently valid legislation.
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VLT HVAC Drive
Design Guide
Software version: 2.0x
These instructions can be used for all VLT HVAC adjustable frequency drives with software
version 2.0x
The software version number can be found in parameter 15-43.
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2.2. CE labeling
2.2.1. CE Conformity and Labeling
What is CE Conformity and Labeling?
The purpose of CE labeling is to avoid technical trade obstacles within the 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.
Adjustable frequency drives 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 an adjustable frequency drive is largely electrical, it does not fall under the Machinery Di-
rective. However, if an adjustable frequency drive is supplied for use in a machine, we provide
information on its safety aspects in the manufacturer's declaration.
The low-voltage directive (73/23/EEC)
Adjustable frequency drives must be CE-labeled 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 uses CE labels in accordance with
the directive and will issue 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 uses CE labels in accordance with
the directive and will issue a declaration of conformity upon request. To carry out EMC-correct
installation, see the instructions in this Design Guide. In addition, we specify the standards with
which our products comply. We offer the filters presented in the specifications and provide other
types of assistance to ensure the optimum EMC result.
The adjustable frequency drive 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.
2.2.2. What Is Covered
The EU " Guidelines on the Application of Council Directive 89/336/EEC " outline three typical sit-
uations of using an adjustable frequency drive. See below for EMC coverage and CE labeling.
1. The adjustable frequency drive is sold directly to the end-consumer. For example, it may
be sold to a DIY market. The end-consumer is a layman. He installs the adjustable fre-
quency drive himself for use with a hobby machine, a kitchen appliance, etc. For such
applications, the adjustable frequency drive must be CE-labeled in accordance with the
EMC directive.
2. The adjustable frequency drive 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 adjustable frequency
drive nor the finished plant must be CE-labeled under the EMC directive. However, the
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unit must comply with the basic EMC requirements of the directive. This is ensured by
using components, appliances and systems that are CE-labeled under the EMC directive.
3. The adjustable frequency drive is sold as part of a complete system. The system is being
marketed as complete and could, for example, be an air-conditioning system. The com-
plete system must be CE-labeled in accordance with the EMC directive. The manufacturer
can ensure CE-labeling under the EMC directive either by using CE-labeled components
or by testing the EMC of the system. If he chooses to use only CE-labeled components,
he does not have to test the entire system.
2.2.3. Danfoss VLT Adjustable Frequency Drive and CE Labeling
CE labeling is a positive feature when used for its original purpose, i.e. to facilitate trade within
the EU and EFTA.
However, CE labeling may cover many different specifications. Thus, you must 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 sense of security when using an adjustable frequency drive as a component in a system or
an appliance.
Danfoss CE labels the adjustable frequency drives in accordance with the low-voltage directive.
This means that if the adjustable frequency drive is installed correctly, we guarantee compliance
with the low-voltage directive. Danfoss issues a declaration of conformity that confirms our CE
labeling in accordance with the low-voltage directive.
The CE label also applies to the EMC directive provided that the instructions for EMC-correct in-
stallation 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 products 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 adjustable frequency drive 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. To assist 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
Electrical Installation .
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2.3. Air humidity
The adjustable frequency drive has been designed to meet the IEC/EN 60068-2-3 standard, EN
50178 pkt. 9.4.2.2 at 122° F [50° C].
2.4. Aggressive Environments
An adjustable frequency drive contains a large number of mechanical and electronic components.
All are vulnerable to environmental effects to some extent.
The adjustable frequency drive should not be installed in environments with airborne
liquids, particles or gases capable of affecting and damaging the electronic compo-
nents. Failure to take the necessary protective measures increases the risk of
stoppages, thus reducing the life of the adjustable frequency drive.
Liquids can be carried through the air and condense in the adjustable frequency drive 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
55. As an extra protection, coated printet circuit boards can be ordered as an option.
Airborne particles such as dust may cause mechanical, electrical or thermal failure in the adjustable
frequency drive. A typical indicator of excessive levels of airborne particles is the presence of dust
particles around the adjustable frequency drive fan. In very dusty environments, use equipment
with enclosure rating IP 55 or a cabinet for IP 00/IP 20/TYPE 1 equipment.
In environments with high temperatures and humidity, corrosive gases such as sulfur, nitrogen
and chlorine compounds will cause chemical processes on the adjustable frequency drive com-
ponents.
Such chemical reactions will rapidly affect and damage the electronic components. In such envi-
ronments, mount the equipment in a cabinet with fresh air ventilation, keeping aggressive gases
away from the adjustable frequency drive.
An extra protection in such areas is a coating of the printed circuit boards, which can be ordered
as an option.
NOTE
Mounting adjustable frequency drives in aggressive environments increases the risk
of stoppages and considerably reduces the life of the drive.
Before installing the adjustable frequency drive, check the ambient air for liquids, particles and
gases. This is done by observing existing installations in this environment. A typical indicator of
harmful airborne liquids is the presence of water or oil on metal parts, or the corrosion of metal
parts.
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Excessive dust particle levels are often found on installation cabinets and existing electrical in-
stallations. One indicator of aggressive airborne gases is the blackening of copper rails and cable
ends on existing installations.
2.5. Vibration and shock
The adjustable frequency drive has been tested according to the procedure based on the shown
standards:
The adjustable frequency drive 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
2.6. Advantages
2.6.1. Why use an adjustable frequency drive for controlling fans and
pumps?
An adjustable frequency drive 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 Laws of
Proportionality
text.
2.6.2. The clear advantage - energy savings
The very clear advantage of using an adjustable frequency drive for controlling the speed of fans
or pumps lies in the electricity savings.
Compared to alternative control systems and technologies, an adjustable frequency drive is the
optimum energy control system for controlling fan and pump systems.
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 rated speed by only 20%, 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 corresponding to 100% a few
days each year, while the average is below 80% of the rated flow for the remainder of the year,
the amount of energy saved is even greater than 50%.
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The laws of proportionality
This figure describes the dependence of flow, pressure and power consumption on rpm.
Q = Flow P = Power
Q
1
= Rated flow P
1
= Rated power
Q
2
= Reduced flow P
2
= Reduced power
H = Pressure n = Speed regulation
H
1
= Rated pressure n
1
= Rated speed
H
2
= Reduced pressure n
2
= Reduced speed
Flow :
Q
1
Q
2
=
n
1
n
2
Pressure :
H
1
H
2
=
(
n
1
n
2
)
2
Power :
P
1
P
2
=
(
n
1
n
2
)
3
2. Introduction to the VLT HVAC Drive VLT
®
HVAC Drive Design Guide
20 MG.11.B4.22 - VLT®is a registered Danfoss trademark.
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