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DFS1/DFS2 Power Installation Guide
Issue Number: 2
4.15
Ground leakage
Suitable measures include either a fixed ground connection or automatic disconnection of the supply
in case of discontinuity of the protective earthing conductor.
4.16
Use of a residual current device (RCD)
There are three common types of ELCB / RCD:
•
AC - detects AC fault currents
•
A - detects AC and pulsating DC fault currents (provided the DC current reaches zero at least
once every half cycle)
•
B - detects AC, pulsating DC and smooth DC fault currents
Type AC should not be used with variable speed drives.
Type A can only be used with single phase drives
Type B is the only type suitable for use with three phase, variable speed drives
If an external EMC filter is used, a delay of at least 50 ms should be incorporated to prevent spurious
tripping. The leakage current is likely to exceed the trip level if all phases are not energized
simultaneously.
4.17
Starts per hour
The number of starts per hour under electronic control is unlimited.
The number of starts per hour caused by interrupting the AC supply is limited to 20 per hour equally
spaced (A minimum interval of 3 minutes between successive starts).
4.18
Start-up time
The time from the instant that power is applied to the drive being ready to run the motor is a
maximum of 5 seconds
4.19
Motor winding voltage
The drive output voltage can adversely affect the inter-turn insulation in the motor. This is because of
the high rate of change of voltage, in conjunction with the impedance of the motor cable and the
distributed nature of the motor winding.
For normal operation with AC supplies up to 500 Vac and a standard motor with a good quality
insulation system, there is no need for any special precautions. In case of doubt, the motor supplier
should be consulted.
Ground leakage
The ground leakage current is > 3.5 mA AC (10 mA DC).
A permanent fixed ground connection must be provided, or other suitable measures taken
to prevent a safety hazard occurring if the connection is lost.
RCD types
Only type B ELCB / RCD are suitable for use with 3 phase inverter drives.
WARNING
NOTE
WARNING
NOTE
Summary of Contents for DFS 1
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