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Diagnostics Optimization CT MODBUS RTU Technical Data
110 Installation and System Design Guide
Issue Number: 1
Thermal protection circuit for the braking resistor
The thermal protection circuit must disconnect the AC supply from the drive if the resistor becomes overloaded due to a fault. Figure 4-23 shows a
typical circuit arrangement.
Figure 4-23 Typical protection circuit for a braking resistor
See section 4.3 Power connections on page 75 for the location of the +DC and braking resistor connections.
4.14 Ground leakage
The ground leakage current depends upon whether the internal EMC filter is installed or not. The drive is supplied with the internal EMC filter
installed. Instructions for removing the internal filter are given in section 4.16.1 Internal EMC filter on page 113.
With internal filter installed:
4.14.1 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.
Size 3 to 5: 28 mA* AC at 400 V 50 Hz
30 µA DC with a 600 V DC bus (10 M)
Size 7 to 11: 56 mA* AC at 400 V 50 Hz
18 µA DC with a 600 V DC bus (33 M)
* Proportional to the supply voltage and frequency.
With internal filter removed: <1 mA
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.
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