# Thyristor-controlled reactor

Canonical URL: https://eloragrid.ai/symbols/thyristor-controlled-reactor
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: TCR
Drawing use: SLD, Schematic
Reference families: IEC, IEEE / ANSI

A shunt reactor in series with anti-parallel thyristors whose firing angle sets the reactive power absorbed.

## In plain English

### What does Thyristor-controlled reactor mean?

A thyristor-controlled reactor is an air-core reactor in series with a pair of anti-parallel thyristor valves. Delaying the firing angle reduces the current conduction period, so the reactor absorbs a continuously adjustable amount of reactive power from zero to its full rating.

### A simple example

Drawings show the reactor symbol with the thyristor pair below it, usually in a delta connection with the reactor split into two halves on either side of the valve. It is the inductive branch of a static var compensator and also appears in some arc furnace compensation schemes.

### What the drawings help you do

Partial conduction generates harmonic currents, mainly odd orders, so the TCR is almost always accompanied by filters. The symbol does not show the filter arrangement or the valve cooling, which is a significant part of the installation.

### This particular reference

A shunt reactor in series with anti-parallel thyristors whose firing angle sets the reactive power absorbed. A TCR varies its absorption continuously; a thyristor-switched reactor is only fully on or fully off.

### Terms

- Terminal: An identified point where a conductor connects.
- Rating: A value stating the conditions for which equipment is specified.
- Schematic: A drawing showing function and connections rather than physical appearance.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [Static Var Compensators (SVC)](https://www.hitachienergy.com/products-and-solutions/facts/static-var-compensation-svc)
- [AutoCAD Electrical: Reactors and inductors](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-BAD50DBF-0951-44A0-BB4C-A57B4A4ED895.htm)


## What it represents

A thyristor-controlled reactor is an air-core reactor in series with a pair of anti-parallel thyristor valves. Delaying the firing angle reduces the current conduction period, so the reactor absorbs a continuously adjustable amount of reactive power from zero to its full rating.
Drawings show the reactor symbol with the thyristor pair below it, usually in a delta connection with the reactor split into two halves on either side of the valve. It is the inductive branch of a static var compensator and also appears in some arc furnace compensation schemes.
Partial conduction generates harmonic currents, mainly odd orders, so the TCR is almost always accompanied by filters. The symbol does not show the filter arrangement or the valve cooling, which is a significant part of the installation.

## How to read it

- The reactor is often drawn in two halves with the valve between them.
- Delta connection cancels triplen harmonics under balanced conditions.

## Information to show or reference

- State reactor rating and firing range.
- Show valve and connection.
- Reference associated filters.

## Important distinction

A TCR varies its absorption continuously; a thyristor-switched reactor is only fully on or fully off.

## Facts

- Control: Firing angle
- Output: Variable inductive Mvar
- Harmonics: Generated during partial conduction
- Preview: Independent educational illustration; consult the applicable standard and project legend for the exact graphic

## Public references

- [Static Var Compensators (SVC)](https://www.hitachienergy.com/products-and-solutions/facts/static-var-compensation-svc) — Hitachi Energy. Public SVC page naming the thyristor-controlled reactor branch.
- [AutoCAD Electrical: Reactors and inductors](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-BAD50DBF-0951-44A0-BB4C-A57B4A4ED895.htm) — Autodesk. Public reactor symbol family context.

## 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.