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The STB NIB 1010 Basic NIM Module
890USE19600 April 2004 27
Selecting a Source Power Supply for the Island’s Logic Power Bus
Logic Power
Requirements
An external 24 VDC power supply is needed as the source for logic power to the
island bus. The external power supply connects to the island’s NIM. This external
supply provides the 24 V input to the built-in 5 V power supply in the NIM.
Characteristics
of the External
Power Supply
The external power supply needs to deliver 24 VDC source power to the island. The
supply that you select can have a low range limit of 19.2 VDC and a high range limit
of 30 VDC. The external supply must be rated safety extra low voltage (SELV-rated).
The SELV-rating means that SELV isolation is provided between the power supply’s
inputs and outputs, the power bus, and the devices connected to the island bus.
Under normal or single-fault conditions the voltage between any two accessible
parts, or between an accessible part and the protective earth (PE) terminal for Class
1 equipment, will not exceed a safe value (60 VDC max.).
Calculating the
Wattage
Requirement
The external supply needs to provide 13 W of power to the NIM.
Suggested
Devices
The external power supply is generally enclosed in the same cabinet as the island.
Usually the external power supply is a DIN rail-mountable unit.
For installations that require 72 W or less from a 24 VDC source power supply, we
recommend a device such as the ABL7 RE2403 Phaseo power supply from
Telemecanique, distributed in the United States by Square D. This supply is DIN rail-
mountable and has a form factor similar to that of the island modules.
If you have room in your cabinet and your 24 VDC power requirements are greater
than 72 W, summable power supply options such as Schneider’s Premium
TSX SUP 1011 (26 W), TSX SUP 1021 (53 W), TSX SUP 1051 (120 W), or
TSX SUP 1101 (240 W) can be considered. These modules are also available from
Telemecanique and, in the United States, from Square D.
CAUTION
IMPROPER GALVANIC ISOLATION
The power components are not galvanically isolated. They are intended for use only
in systems designed to provide SELV isolation between the supply inputs or outputs
and the load devices or system power bus. You must use SELV-rated supplies to
provide 24 VDC source power to the island.
Failure to follow this precaution can result in injury or equipment damage.