Danfoss VLT HVAC Drive FC 102 Application guide
VLT® HVAC Drive FC 102 Application Note 1 Temperature Derating Guide
1 Temperature Derating Guide
1.1.1 Abstract
This paper provides detailed data regarding the operation of the VLT HVAC Drive FC102 at varying
ambient temperature and load. There is given application specific guidelines, and the influence
on the switching frequency is documented.
1.1.2 Introduction
This paper provides detailed information regarding the operation of the VLT HVAC Drive FC102 at
different ambient temperature and load conditions. Application specific guidelines are given and
the influence of the switching frequency is detailed.
VLT HVAC Drive FC102 General Specifications
The VLT HVAC Drive FC102 has a specified continuous output current to be able to supply a wide
range of motors with different efficiencies. Full continuous rated output current can be supplied
in ambient temperatures up to 45°C. With a typical full load current of EFF2 motors (see
Efficiency
in ambient temperatures up to 50°C.
Frequency Converter Selection and Derating
The sizing of the frequency converter is generally dependant on a number of factors including:
), full output shaft power can be maintained with the VLT HVAC Drive FC102 operating
• Motor efficiency and full load current
• Ambient temperature
• Mains supply voltage
• Motor cable length and type (e.g. screened or unscreened)
• Number of options installed (impacts the internal temperature within the frequency converter)
• Switching frequency and/or switching pattern (impacts the heat generation within the
frequency converter)
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Motor
Motor Efficiency
EFF classification of motors is predominantly relevant in European Union countries although it is
also adopted or being considered to be adopted in other countries. It is applicable to specific motor
types (e.g. totally enclosed fan ventilated, three phase AC squirrel cage induction motors in the
range 1.1 to 90kW, having 2 or 4 poles, rated for 400V, 50Hz, S1 duty class).
Other motor efficiency classifications or Minimum Efficiency Performance Standards (MEPS) exist
elsewhere in the world. For example in North America NEMA MG1 defines motor efficiency levels
for “energy efficient” and “premium efficiency” motors for a wider range of motors than those
under the EFF classification (e.g. 1 to 500HP, 2, 4 and 6 pole) and in Australia and New Zealand
AS/NZS 1359.5-2004, applicable to three phase, 2, 4, 6 and 8 pole motors from 0.73kW to
<185kW, defines minimum efficiency levels approximately equivalent to those of the European
EFF1 level and high efficiency motors as having an even higher efficiency. Some of these efficiency
requirements are voluntary and others are legally enforceable.
The efficiency of a motor is one factor that affects the full load current rating of a motor and
therefore has an impact on the ambient temperature rating of the frequency converter for use
with that motor when operating at full load. For example the frequency converter may be rated
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1 Temperature Derating Guide VLT® HVAC Drive FC 102 Application Note
for operation in an ambient temperature of say 50 °C when operating at full load current of a
15kW EFF2 motor but it may be rated for operation in say 54 °C when operating at full load current
of a 15kW high efficient motor according to AS/NZS 1359.5-2004 or rated for operation in say 52
°C when operating at full load current of a 20HP premium efficiency motor according to NEMA
MG1.
Ambient Temperature
If the maximum ambient temperature in which the frequency converter will be installed is equal
to or below the limit defined for full continuous FC output current in the
the
Operating Instructions
Guide
and if the factory default switching frequency will be used, there is no need to consider
derating of the output current.
However if the maximum ambient temperature is higher than that defined, this guide should be
used to ensure the derated continuous output current of the frequency converter at this higher
maximum ambient temperature is higher than the full load current of the motor or at least higher
than the maximum running current of the motor for the application.
Mains supply voltage
The mains supply voltage has a minimal affect for low powers and therefore the ambient temperature rating, current rating and derating curves are shown for the worst case situation (i.e.
highest mains voltage). For higher powers (enclosure size D and above), different derating curves
dependant on the mains supply voltage are shown.
or the
General Specifications and Troubleshooting section
Specifications section
of the
Design
of
Motor cable length and type
The motor cable length and type has an affect because due to the high switching frequency of
the frequency converter it not only has to supply the full load current of the motor but also
“charging” currents in the motor cable. The longer the motor cable or if the cable is screened
instead of unscreened, the higher these charging currents. The motor cable length and type has
more affect at low powers and much less at higher powers. For all powers the ambient temperature, current rating and derating curves are given for the worst case situation (150m screened/
300m unscreened motor cable).
Number of options installed
The frequency converter can have up to three options installed (Option A (BMS high level interface
communication options), Option B (I/O extension options) and Option C (application options) ).
The number of options installed can affect the internal temperature of the frequency converter
(depending on enclosure size). Therefore for some enclosure sizes different derating curves are
shown depending on the number of options installed.
Switching frequency, switching pattern and automatic adaptation
The frequency converter can be programmed to use a different switching pattern (60 AVM or
SFAVM (parameter 14-00)) or switching frequency (1kHz to 16kHz (depending on size) (parameter
14-01)).
For most applications the default settings (60 AVM and 4kHz (depending on size)) will be adequate
because the frequency converter automatically adapts these to ensure performance if necessary.
The frequency converter constantly checks for critical levels of internal temperature, load current,
high voltage on the intermediate circuit and low motor speeds. As a response to a critical level,
the frequency converter can adjust the switching frequency and/or change the switching pattern
in order to ensure the performance of the frequency converter. The capability to automatically
reduce the output current (i.e. automatically derate the output current) extends the acceptable
operating conditions even further. This automatic ad aptation function ensures continued operation
of the fan, pump or compressor even in extreme operating conditions. It also helps to minimize
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VLT® HVAC Drive FC 102 Application Note 1 Temperature Derating Guide
the acoustic noise from the motor resulting from the frequency converter when operating at low
speeds, which is the most critical area of operation for acoustic noise because at low speeds the
acoustic noise from the motor and fan themselves is low.
The graphs that follow provide information about the mutual influence on load, ambient temperature, switching frequency, and switching pattern.
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1.1.3 Motor Acoustic Noise Optimization
Additional acoustic noise from a motor when using a frequency converter can be a concern on
some applications. On pump or compressor applications it is typically not a concern but on fan
applications it may be. Typically it is a concern when the fan is operating at mid to low speeds.
At high speeds any additional noise as a result of the frequency converter, is drowned out by the
noise from the motor and fan themselves but at mid to low speeds it may be noticeable.
Changing the switching frequency to a higher value can help to reduce acoustic noise from the
motor and is the most common solution to this.
Changing the switching pattern from the default setting is not often done. However, the acoustic
noise from a motor will typically be less when using SFAVM than 60 AVM for the same switching
frequency, although the internal frequency converter losses will be higher. The automatic adaptation function described above sets the switching pattern to SFAVM when operating at low output
frequencies (approximately <30% nominal motor frequency) to help minimize acoustic motor
noise. It also sets the switching pattern to 60 AVM when operating at high output frequencies
(approximately >80% of nominal motor frequency) to help minimize internal losses when the
frequency converter load is at its highest (particularly applicable to fans, centrifugal pumps and
centrifugal chiller compressors.) To minimize acoustic motor noise in the operating range between
approximately 30% and 80% motor nominal frequency a combination of changing the switching
pattern and/or switching frequency can give the best results.
However, if the switching frequency is increased and depending on the application, if t he switching
pattern is changed from default, this can result in increased full load losses in the frequency converter and therefore the continuous current rating of the frequency converter should be derated
in accordance with the graphs that follow.
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1 Temperature Derating Guide VLT® HVAC Drive FC 102 Application Note
1.1.4 Application Dependant Derating
Fans, centrifugal pumps and centrifugal chiller compressors
Due to the nature of these loads the maximum load (i.e. output current) occurs at nominal/maximum output frequency. The automatic adaptation function described above, ensures that when
the frequency converter is operating at its highest load and therefore when its internal losses are
greatest, it is operating with 60 AVM switching pattern irrespective of what the switching pattern
(parameter 14-00) is programmed to. Therefore for these applications it is only necessary to refer
to the graphs that follow in illustration 1.1 - 1.9 even if the switching pattern parameter is changed
from default to minimize motor audible noise at mid to low output frequencies.
Screw, scroll and reciprocating compressors
Due to the nature of these loads the maximum load (i.e. output current) could occur at all output
frequencies (e.g. the torque and current required to operate a screw compressor at 60% speed
will typically be similar to that at 100% speed.) Therefore for these applications it is necessary to
refer to either the graphs in illustration 1.1 - 1.9 (60 AVM) OR the graphs in illustration 1.10 - 1-18
(SFAVM), depending on the switching pattern programmed (parameter 14-00.) Typically this parameter will not be changed from default, so only the graphs in illustration 1.1 - 1.9 need be used,
but additional graphs are shown in illustration 1.10 - 1-18 for SFAVM switching pattern for completeness. (SFAVM results in higher internal losses than 60 AVM and therefore the derating factors
are different.)
1.1.5 How to Find the Derating Factor
1. Determine the application.
1a If it is a fan, centrifugal pump or centrifugal compressor use steps 2 to 4 to
determine which graph applies from illustration 1.1 - 1.9.
1b If it is a screw, scroll or reciprocating compressor and the switching pattern
(parameter 14-00) is not changed from default (60 AVM), use steps 2 to 4 to
determine which graph applies from illustration 1.1 - 1.9.
1c If it is a screw, scroll or reciprocating compressor and the switching pattern
(parameter 14-00) has been changed from default to SFAVM, use steps 2 to 4
to determine which graph applies from illustration 1.10 - 1-18.
2. Find the enclosure type from the tables below, e.g. a 7.5 kW with mains supply 3 x 380
– 480 V and IP 55 rating is enclosure type A5.
3. If the drive is enclosure type D or E then take note of the supply voltage for the drive.
4. Find the relevant derating curve based on the information found above: a pplicat ion and
switching pattern, enclosure type and supply voltage (if relevant).
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VLT® HVAC Drive FC 102 Application Note 1 Temperature Derating Guide
1.1.6 Enclosure Types
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3 x 200 – 240 Volt
IP 20 / chassis A2 A3 B3 B4 B4 C3 C4
IP 21 / NEMA 1 A2 A3 B1 B2 C1 C1 C2
IP 55 / NEMA 12 A5 A5 B1 B2 C1 C1 C2
IP 66 / NEMA 12
3 x 380 - 480 Volt
IP 00 - - - - - - D3 D4 E2
IP 20 / chassis A2 A3 B3 B4 C3 C4 - - IP 21 / NEMA - - B1 B2 C1 C2 D1 D2 E1
IP 54-55 / NEMA
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IP 66 / NEMA 12 A5 A5 B1 B2 C1 C2 - - -
3 x 525 - 600 Volt
IP 00 - - - - - - D3 D4 E2
IP 20 / chassis A2 A3 B3 B4 C3 C4 - - IP 21 / NEMA 1 A2 A3 B1 B2 C1 C2 D1 D2 E1
IP 54-55 / NEMA
12
IP 66 / NEMA 12 A5 A5 B1 B2 C1 C2 - - -
1,1-2,2 kW 3-3,7 kW 5 5-11 kW 15 kW 18,5 kW 22-30 kW 37-45 kW
A5 A5 B1 B2 C1 C1 C2
1,1-4kW5,5-7,5kW11-18,
5 kW
A5 A5 B1 B2 C1 C2 D1 D2 E1
1,1-4kW5,5-7,5kW11-18,
A5 A5 B1 B2 C1 C2 D1 D2 E1
22-37kW45-55kW75-90kW110-13
22-37kW45-55kW75-90kW110-13
5 kW
2 kW
2 kW
160-25
0 kW
160-31
5 kW
315-45
0 kW
355-56
0 kW
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