3.5.3 Power supply system requirements
Definition of the power supply system
IEC 60364 defines three different types of mains grounding using the two-letter
codes. These are TN, TT, and IT.
Type of ground connectionFirst letter
Direct connection of one point to ground.T
Not connected to ground or connected to ground via a high impedance.I
Connection between ground and the device being suppliedSecond letter
Direct connection of one point to ground.T
Direct connection to neutral at the origin of installation, which is connec-
ted to the ground
N
In the following section the transformer configuration refers to the transformer
secondary side. Configuration of the transformer primary side is not discussed in
this context.
Allowed power supply systems
Only the following systems are allowed by ABB:
TN−C systemTN−S system
A combined PEN conductor is used as both
a PE and an N conductor.
PE and N are separate conductors that are
connected together only near the transformer.
xx1700001311
xx1700001310
Note
The networks must be symmetrical with respect to protective earth.
Isolation transformer
A three-phase isolation transformer between the mains supply and the control
cabinet is required for any of the below conditions:
• If the available grid do not comply with the above described allowed power
systems, as mentioned in Allowed power supply systems on page 79.
• When the mains supply is shared with a pressing machine, frequency
converter, or other large industry equipment that may cause the power supply
Continues on next page
Product manual - OmniCore V250XT Type B 79
3HAC087112-001 Revision: A
© Copyright 2023-2023 ABB. All rights reserved.
3 Installation and commissioning
3.5.3 Power supply system requirements
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