# Separate excitation device

Canonical URL: https://eloragrid.ai/protection-functions/31-separate-excitation-device
Publisher: Elora Grid
Updated: 2026-10-13
Lookup label: 31
Drawing use: SLD, Schematic
Reference families: IEEE / ANSI

Connects or controls a separately supplied excitation arrangement for a machine.

## What it represents

Connects or controls a separately supplied excitation arrangement for a machine.
In a drafting package, connect this reference to the separate excitation supply and machine field connection. The associated drawing should trace the excitation switching command and sequence references; the number identifies the role and does not specify the terminal arrangement, ratings or operating settings.
This designation is useful when reading machine and legacy control drawings. Retain the documented function on an existing drawing and consult the original equipment manual before assigning it to a new design.

## How to read it

- Identify the separate excitation supply and machine field connection.
- Trace the excitation switching command and sequence references.

## Information to show or reference

- Label the separate excitation supply and machine field connection.
- Cross-reference the excitation switching command and sequence references.
- Identify the device tag, manual revision and logic drawing that define this implementation.

## Important distinction

This specialist machine-control reference should be interpreted with the excitation drawing; device 41 identifies a field breaker.

## Facts

- ANSI / IEEE function number: 31
- Drawing context: The separate excitation supply and machine field connection
- Application scope: Specialist or legacy machine-control use; interpret with the equipment legend.

## Public references

- [ANSI device-number and suffix reference table](https://selinc.com/pt/products/tables/ansi/) — Schweitzer Engineering Laboratories. Public manufacturer number/name association. Drafting explanations are independently written.
- [IEEE C37.2-2022: power-system device function numbers](https://ieeexplore.ieee.org/document/9984140) — IEEE. Normative device-number publication; exact edition wording and compliance require the licensed standard.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.