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78
Affinity User Guide
www.controltechniques.com Issue Number: 5
4.9.3 Braking resistor software overload protection
The drive software contains an overload protection function for a braking
resistor. In order to enable and set-up this function, it is necessary to
enter two values into the drive:
•
Resistor short-time overload time (Pr
10.30
)
•
Resistor minimum time between repeated short-time overloads
(Pr
10.31
)
This data should be obtained from the manufacturer of the braking
resistors.
Pr
10.39
gives an indication of braking resistor temperature based on a
simple thermal model. Zero indicates the resistor is close to ambient and
100% is the maximum temperature the resistor can withstand. A br.rS
alarm is given if this parameter is above 75% and the braking IGBT is
active. An It.br trip will occur if Pr
10.39
reaches 100%, when Pr
10.37
is
set to 0 (default value) or 1.
If Pr
10.37
is equal to 2 or 3 an It.br trip will not occur when Pr
10.39
reaches 100%, but instead the braking IGBT will be disabled until
Pr
10.39
falls below 95%. This option is intended for applications with
parallel connected DC buses where there are several braking resistors,
each of which cannot withstand full DC bus voltage continuously. With
this type of application it is unlikely the braking energy will be shared
equally between the resistors because of voltage measurement
tolerances within the individual drives. Therefore with Pr
10.37
set to 2 or
3, then as soon as a resistor has reached its maximum temperature the
drive will disable the braking IGBT, and another resistor on another drive
will take up the braking energy. Once Pr
10.39
has fallen below 95% the
drive will allow the braking IGBT to operate again.
See the
Advanced User Guide
for more information on Pr
10.30
, Pr
10.31
, Pr
10.37
and Pr
10.39
.
This software overload protection should be used in addition to an
external overload protection device.
4.10 Ground leakage
The ground leakage current depends upon whether the internal EMC
filter is installed. The drive is supplied with the filter installed. Instructions
for removing the internal filter are given in Figure 4-20
internal EMC filter (size 1 to 3)
With internal filter installed:
Size 1 to 3:
28mA* AC at 400V 50Hz
30µA DC with a 600V DC bus (10M
Ω
)
Size 4 to 6:
56mA* AC at 400V 50Hz
18µA DC with a 600V DC bus (33M
Ω
)
* Proportional to the supply voltage and frequency.
With internal filter removed:
<1mA
Note that in both cases there is an internal voltage surge protection
device connected to ground. Under normal circumstances this carries
negligible current.
4.10.1 Use of residual current device (RCD)
There are three common types of ELCB / RCD:
1. AC - detects AC fault currents
2. A - detects AC and pulsating DC fault currents (provided the DC
current reaches zero at least once every half cycle)
3. B - detects AC, pulsating DC and smooth DC fault currents
•
Type AC should never be used with drives.
•
Type A can only be used with single phase drives
•
Type B must be used with three phase drives
If an external EMC filter is used, a delay of at least 50ms should be
incorporated to ensure spurious trips are not seen. The leakage current
is likely to exceed the trip level if all of the phases are not energized
simultaneously.
4.11 EMC (Electromagnetic compatibility)
The requirements for EMC are divided into three levels in the following
three sections:
Section 4.11.3, General requirements
for all applications, to ensure
reliable operation of the drive and minimize the risk of disturbing nearby
equipment. The immunity standards specified in section 11 will be met,
but no specific emission standards. Note also the special requirements
given in
Surge immunity of control circuits - long cables and connections
on page 86 for increased surge immunity of control
circuits where control wiring is extended.
Section 4.11.4, Requirements for meeting the EMC standard for
power drive systems, IEC61800-3 (EN 61800-3:2004)
.
Section 4.11.5, Requirements for meeting the generic emission
standards
for the industrial environment, IEC61000-6-4, EN 61000-6-
4:2007.
The recommendations of section 4.11.3 will usually be sufficient to avoid
causing disturbance to adjacent equipment of industrial quality. If
particularly sensitive equipment is to be used nearby, or in a non-
industrial environment, then the recommendations of section 4.11.4 or
section 4.11.5 should be followed to give reduced radio-frequency
emission.
Fire Mode - Important Warning
When Fire Mode is active the motor overload and thermal
protection are disabled, as well as a number of drive
protection functions. Fire Mode is provided for use only in
emergency situations where the safety risk from disabling
protection is less than the risk from the drive tripping -
typically in smoke extraction operation to permit evacuation
of a building. The use of Fire Mode itself causes a risk of fire
from overloading of the motor or drive, so it must only be
used after careful consideration of the balance of risks.
Care must be taken to prevent inadvertent activation or de-
activation of Fire Mode. Fire Mode is indicated by a flashing
display text warning "Fire mode active".
Care must be taken to ensure that parameters Pr
1.53
or
Pr
1.54
are not inadvertently re-allocated to different inputs or
variables. It should be noted that, by default, Pr
1.54
is
controlled from digital input 4 and changing Pr
6.04
or Pr
8.24
can re-allocate this digital input to another parameter. These
parameters are at access level 2 in order to minimize the risk
of inadvertent or unauthorized changes. It is recommended
that User Security be applied to further reduce the risk (see
section 5.10
Parameter access level and security
page 97). These parameters may also be changed via serial
communications so adequate precautions should be taken if
this functionality is utilized.
WARNING
When the internal filter is installed the leakage current is
high. In this case a permanent fixed ground connection must
be provided, or other suitable measures taken to prevent a
safety hazard occurring if the connection is lost.
Only type B ELCB / RCD are suitable for use with 3 phase
inverter drives.
WARNING
WARNING
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