Special Installation Instructions For Floating Neutral (It) Systems; Definition Of Floating Neutral Systems - GE 90-30 PLC Series Installation And Hardware Manual

Special Installation Instructions for Floating Neutral (IT) Systems

When the AC input power supplies listed below are installed in a system where the Neutral line is
not referenced to Protective Earth Ground, these special installation instructions must be followed
to prevent damage to the power supply.

Definition of Floating Neutral Systems

A Floating Neutral System is a system of power distribution wiring where Neutral and Protective
Earth Ground are not tied together by a negligible impedance. In Europe this is referred to as an
IT system (see IEC950). In a Floating Neutral System, voltages measured from input terminals to
protective earth ground may exceed the 264 Volts AC maximum input voltage specified in the
power supply specifications in Chapter 24in this manual.
Example of Floating Neutral System
This system must be installed using the special installation instructions on the following page.
Systems in which one leg of the power distribution wiring is tied to Protective Earth or a tap
between two legs of the power distribution wiring is tied to Protective Earth are not Floating
Neutral Systems.
Examples of Non-Floating Neutral System
These non-floating neutral systems do not require these special installation instructions.
GFK-0356Q Chapter 2 Installation
IC693PWR321S (or later version)
IC693PWR330A (or later version)
L1
N
PE
L1
N
PE
L
N/PE
2
L1
L2
PE
2-25