Motor Starting Currents; Coordinating The Components Of The Motor Circuit - Siemens NXAIR Operating Instructions Manual

Operating the contactor panel with panel width 435 mm

13.19 Motor starting currents

Due to the arising motor starting current, the instant when the motor starts represents the maximum stress
for the HV HRC fuse-link. Motor starting currents are dependent on the starting time and the starting
frequency.
The latest motor protection tables with HV HRC fuse-links type HHM are available in the download area of
the SIBA company: www.siba-fuses.com
These motor protection tables show the correspondence between the maximum permissible starting currents
of downstream HV motors (depending on the starting time and the starting frequency) and the associated
HV HRC fuse-links.

13.20 Coordinating the components of the motor circuit

The illustration given below shows the coordination of a HV HRC fuse-link characteristic with a motor
characteristic as an example:
Fig. 261: Example for the coordination of a HV HRC fuse-link characteristic 125 A with a motor characteristic
The latest time-current characteristics for HV HRC fuse-links type HHM are available in the download site of
the SIBA company: www.siba-fuses.com
Coordination
Rules for coordinating the components of the motor circuit:
•
The time-current characteristic must be located on the right of the motor starting current (point A).
•
The rated current of the HV HRC fuse-link must exceed the normal current of the motor.
•
The current corresponding to the intersection B of the HV HRC fuse-link characteristic and the
characteristic of the time-overcurrent protection must be higher than the minimum breaking current of
the HV HRC fuse-link.
•
If this is not feasible, it must be ensured that overload currents that are smaller than the minimum
breaking current of the HV HRC fuse-link are interrupted by the switching-device via the striker. This
prevents thermal overloading of the HV HRC fuse-link, which would otherwise be destroyed.
146
INFORMATION
Final procedure steps
Next, insert the contactor truck into the panel. After closing the high-
voltage door, the panel can be integrated into the course of operation
again.
NXAIR / ≤ 40 kA
Characteristic of the
(1)
HV HRC fuse-link
(2) Motor starting current
(3) Motor starting time
Characteristic of the
(4)
time-overcurrent protection
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