1. What's on the Wiring Diagram? (5 Categories of Information)
| Information | Example | Function |
|---|---|---|
| Phase sequence | L1/L2/L3 | Defines the three-phase arrangement order |
| Neutral conductor | N | Neutral conductor, carries current |
| Protective conductor | PE | Protective grounding, no current under normal conditions |
| Terminal number | 1/2/3/4/5 | Corresponds to the terminal block |
| Cross-section | 2.5mm²/4mm² | Conductor size |
2. L1/L2/L3/N/PE Arrangement Rules (Horizontal and Vertical)
Terminal arrangement follows theleft to right, top to bottomrule:
| Arrangement | Order | Color coding |
|---|---|---|
| Horizontal, left to right | L1→L2→L3→N→PE | Yellow → Green → Red → Blue → Yellow-Green |
| Vertical, top to bottom | L1→L2→L3→N→PE | Yellow → Green → Red → Blue → Yellow-Green |
| Two tiers | Upper tier L1/L2/L3 | Lower tier N/PE |
3. Phase sequence color coding (GB/T 6995)
GB/T 6995 Cable phase colors are specified as:
L1 = ●Yellow
L2 = ●Green
L3 = ●Red
N = ●Blue
PE = ●Yellow-green striped
Wrong color coding leads to wrong phase sequence, and the motor runs in reverse.
4. How to read a terminal block (Top to Bottom)
Terminal numbering runs from top to bottom:Terminal 1 to L1, terminal 2 to L2, terminal 3 to L3, terminal 4 to N, terminal 5 to PE. Multi-tier terminal blocks: first tier L1/L2/L3, second tier N/PE. Crimp one wire per terminal — never two wires in one terminal.
5. Common Wiring Diagram Mistakes (3 red lines)
① N and PE tied together— current flows in the N conductor, so tying it to PE energizes the enclosure; ② Wrong phase sequence— L1/L2/L3 out of order, so the motor runs in reverse; ③ Multiple wires in one terminal— two or more wires crimped in a single terminal, causing poor contact and overheating.
FAQ FAQ
On a three-phase four-wire diagram, where is the PE conductor?
The PE conductor comes last — rightmost in a horizontal layout, bottom in a vertical layout. The PE bar and the N bar must be kept separate, and the PE bar bonds to the enclosure.
Can two wires be crimped in one terminal?
Not recommended. One wire per terminal is the most reliable; multiple wires in one terminal cause poor contact. Two-tier terminals can be used in special cases.
What if the phase sequence is wrong?
Check it with a phase sequence meter before energizing. If it is wrong, swap any two phase conductors to correct it.
Can the N conductor be left unconnected?
No. In a three-phase four-wire system the N conductor is the working conductor; leaving it unconnected shifts the voltage across single-phase loads and burns out equipment.
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