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What do the red, yellow and green wires mean?

Oct 08, 2018

1, according to the wire color marking circuit

Black - internal wiring of devices and equipment.

Brown - the positive pole of the DC circuit.

Red - phase C of a three-phase circuit;

a collector of a semiconductor transistor;

A cathode of a semiconductor diode, a rectifier diode, or a thyristor.

Yellow - phase A of a three-phase circuit;

The base of the semiconductor transistor;

The control pole of the thyristor and the triac.

Green - Phase B of a three-phase circuit.

Blue - the negative pole of the DC circuit;

The emitter of a semiconductor transistor;

The anode of a semiconductor diode, rectifier diode or thyristor.

Light blue - the neutral or neutral of a three-phase circuit; the grounded neutral of a DC circuit.


The main electrode of the triac; no semiconductor circuit of the specified color.

Yellow and green two colors (each color is about 15 to 100 mm alternately attached) - a safe grounding wire.

Red and black parallel—AC circuits connected by two-core wires or two twisted wires.

2. When selecting the color of the wire according to the circuit

AC three-phase circuit

Phase A: yellow; Phase B: Green; Phase C: Red;

Neutral or neutral: light blue; Safety ground wire: yellow and green.

AC circuit connected by double-core wire or double stranded wire

Red and black in parallel.

DC circuit

Positive: brown; negative: blue; grounded neutral: light blue.

Semiconductor circuit

Collector of semiconductor triode: red; base: yellow; emitter: blue. Anode of semiconductor diode and rectifier diode: blue; cathode: red.

Anode of thyristor tube: blue; control electrode: yellow; cathode: red.

Control electrode of the two-way thyristor: yellow; main electrode: white.

Internal wiring of the entire device and equipment is generally recommended: black; semiconductor circuit: white;

When there is confusion: allow the selection of other colors outside the color (such as: orange, purple, gray, green blue, rose, etc.).

 Specific color

On a wire, if there are two or more kinds of calibratable colors, depending on the specific condition of the circuit, the color is fixed according to a certain meaning that needs to be expressed in the circuit.

 Schedule: National three-phase wire color requirements standard

In addition, Xiao Bian added another sentence: countries have regional differences, specific analysis of specific situations, can not be dogmatic, pay special attention to the maintenance of imported equipment, the multimeter measurement is subject to actual. Some friends have repaired German, Swiss equipment, 24v positive and negative are blue control loop wires, there are orange positive, white negative, green ground; the United States is, blue is positive, blue and white are negative. So the above content provides a reference, everyone progress together!

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