Ground Leakage - Emerson Unidrive M700 Installation Manual

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 resistor. The braking resistor
thermal time constant can be calculated from resistor data sheet values using the following equation:
Resistor pulse power rating x Braking time
Pr 10.031
------------------------------------------------------------------------------------------------------------------------- -
=
Resistor continuous power rating
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 Internal EMC filter on page 65.
With internal filter installed:
Size 3 to 4:
28 mA* AC at 400 V 50 Hz
30 µA DC with a 600 V DC bus (10 MΩ)
* Proportional to the supply voltage and frequency.
With internal filter removed:
<1 mA
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.
WARNING
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Unidrive M/HS Frame 3 and 4 Power Installation Guide
Issue Number: 3