68
Unidrive M702 User Guide
Issue Number: 3
Figure 4-18 Typical protection circuit for a braking resistor
See Figure 4-1 on page 51 and Figure 4-4 on page 53 for the location of
the +DC and braking resistor connections.
4.10.3 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 three values into the drive:
•
Braking Resistor Rated Power
(10.030)
•
Braking Resistor Thermal Time Constant
(10.031)
•
Braking Resistor Resistance
(10.061)
This data should be obtained from the manufacturer of the braking
resistors.
Pr
10.039
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 ‘Brake
Resistor’ alarm is given if this parameter is above 75 % and the braking
IGBT is active. A Brake R Too Hot trip will occur if Pr
10.039
reaches
100 %, when Pr
10.037
is set to 0 (default value) or 1.
If Pr
10.037
is equal to 2 or 3, a Brake R Too Hot trip will not occur when
Pr
10.039
reaches 100 %, but instead the braking IGBT will be disabled
until Pr
10.039
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
10.037
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
10.039
has fallen below 95 % the drive will allow the braking IGBT to
operate again.
See the
Parameter Reference Guide
for more information on Pr
10.030
,
Pr
10.031
, Pr
10.037
and Pr
10.039
.
This software overload protection should be used in addition to an
external overload protection device.
4.11 Ground leakage
The ground leakage current depends upon whether the internal EMC
filter is installed or not. The drive is supplied with the filter installed.
Instructions for removing the internal filter are given in section
4.12.2
With internal filter installed:
Size 3:
28 mA* AC at 400 V 50 Hz
30 µA DC with a 600 V DC bus (10 M
Ω
)
Size 4:
9.5 mA* AC at 400 V 50 Hz
36 µA DC with a 600 V DC bus (10 M
Ω
)
Size 6:
* Proportional to the supply voltage and frequency.
With internal filter removed:
Size 3:
<1 mA
4.11.1 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 50 ms 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.
4.12 EMC (Electromagnetic compatibility)
The requirements for EMC are divided into three levels in the following
three sections:
Section 4.12.3, General requirements
for all applications, to ensure
reliable operation of the drive and minimise the risk of disturbing nearby
equipment. The immunity standards specified in Chapter 12
on page 227 will be met, but no specific emission standards are
applied. Note also the special requirements given in
control circuits - long cables and connections outside a building
page 76 for increased surge immunity of control circuits where control
wiring is extended.
Section 4.12.4, Requirements for meeting the EMC standard for
power drive systems, IEC61800-3 (EN 61800-3:2004)
.
Section 4.12.5, Requirements for meeting the generic emission
standards
for the industrial environment, IEC61000-6-4, EN 61000-6-
4:2007.
The recommendations of section 4.12.3 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 4.12.4 or
section 4.12.5 should be followed to give reduced radio-frequency
emission.
In order to ensure the installation meets the various emission standards
described in:
•
The EMC data sheet available from the supplier of the drive
•
The Declaration of Conformity at the front of this manual
•
The correct external EMC filter must be used and all of the guidelines in
section 4.12.3
Compliance with generic emission standards
followed.
Optional
EMC
filter
Stop
Start /
Reset
Thermal
protection
device
Braking resistor
Drive
Main contactor
power supply
+DC
BR
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
Summary of Contents for Unidrive M702
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