3-Phase Plug Wiring Diagram

3-Phase Plug Wiring Diagram — interactive diagram. Open it in the editor to customise components and wiring.

This is a free printable 3 phase plug wiring diagram: download the diagram as SVG or open it and print to paper or PDF.

A 3-phase plug wiring diagram shows how to connect the three line conductors, neutral, and earth to the correct pins of an IEC 60309 (CEE) industrial plug — with pin position, colour coding, and clock-face hour key varying by voltage, current, and frequency rating.

IEC 60309 plugs (commonly called CEE plugs, Commando plugs, or Ceeform connectors in industry) are the global standard for industrial and commercial 3-phase connections. They are circular, keyed, and weatherproof — designed to be unambiguous and safe in harsh environments.

Key identification system: IEC 60309 plugs are identified by colour, diameter, and a clock-face position of the earth pin. The clock-face hour (3h, 6h, 9h, etc.) indicates voltage and frequency range, preventing the connection of equipment to the wrong supply. - Red body: 380–415 V AC 3-phase (50 Hz at 6h position) - Blue body: 200–250 V AC single-phase or 3-phase (50 Hz at 6h) - Yellow body: 20–25 V AC - Black body: additional DC and special-frequency ratings

Common 3-phase red plug pin layout (5-pin, 16 A or 32 A): - PE (Earth): the pin at the very top of the plug face (the key pin, at the 12 o'clock position for the earth groove) - N (Neutral): pin designated N, offset from earth - L1, L2, L3 (Line conductors): the three phase pins, evenly spaced

Exact pin positions in the plug body are standardised — each pin socket is at a fixed angular position, and the earth pin profile is unique to prevent incorrect insertion. The plug body itself is keyed so it can only engage the socket at the correct rotational position.

Conductor colour coding (IEC/European standard, IEC 60446): - L1: Brown - L2: Black (note: in older UK wiring, Red) - L3: Grey (note: in older UK wiring, Yellow) - N: Blue (note: in older UK wiring, Black) - PE: Green/Yellow striped

For North American connections, NEMA configurations are used instead of IEC 60309. No direct colour-to-pin equivalence should be assumed between the two systems.

Always check whether the connected equipment requires a neutral conductor. Some 3-phase loads (motors, heaters) use only L1/L2/L3 and PE (4-pin plugs). Others require neutral for control circuits or single-phase loads within a 3-phase system (5-pin plugs).

How to wire 3 phase plug wiring diagram

Confirm the supply voltage, current, and frequency, and select the correct plug Match the plug colour (red = 380–415 V, blue = 200–250 V), current rating (16 A, 32 A, 63 A, 125 A), and hour position (6h for 50 Hz) to the supply and equipment specifications before purchasing the plug.
Isolate and lock out the supply circuit Switch off and lock the circuit breaker or isolator feeding the socket. Verify dead with a calibrated voltage tester at the socket pins before opening any plug or socket bodies.
Open the plug body and identify each terminal Unscrew the plug body halves. Inside, each terminal is marked: PE (earth), N (neutral if 5-pin), L1, L2, L3. Note the colour of each cable grip position and map to the cable cores before inserting conductors.
Prepare the cable conductors Strip the cable outer sheath to the correct length for the plug's cable clamp. Strip individual conductors to expose 8–12 mm of copper (or per the plug's terminal specification). Do not nick the conductor strands.
Insert and torque each conductor to the correct terminal PE (green/yellow) to the PE terminal, blue to N, brown to L1, black to L2, grey to L3. Torque the terminal screws to the plug manufacturer's specification using a calibrated torque screwdriver. Under-torqued terminals arc and overheat under load.
Secure the cable in the strain relief clamp Tighten the cable gland or clamp so that mechanical force on the cord is transferred to the plug body, not to the terminal connections. The outer sheath of the cable must be clamped, not the individual cores.
Close the plug and test continuity and insulation resistance Reassemble the plug body. Before energising, test that the PE terminal has continuity to the cable earth core, and that insulation resistance between conductors and earth is acceptable (typically >1 MΩ). Then restore supply and test under load.

Specifications

Standard	IEC 60309 / EN 60309
Plug body colour (3-phase 380–415 V)	Red
Earth pin hour position (50 Hz, 380–415 V)	6h
Common current ratings	16 A, 32 A, 63 A, 125 A
L1 conductor colour (IEC 60446)	Brown
L2 conductor colour (IEC 60446)	Black
L3 conductor colour (IEC 60446)	Grey
N conductor colour	Blue
PE conductor colour	Green/Yellow striped

Safety warnings

All fixed installation work on 3-phase systems must be carried out by a licensed electrician and must comply with IEC 60364, BS 7671, NEC/NFPA 70, AS/NZS 3000, or the applicable national standard. Three-phase voltages (380–415 V and above) are lethal.
Always isolate, lock out, and verify dead before opening any plug, socket, or enclosure. The voltage between line conductors on a 400 V system is 400 V — far above the 230 V line-to-neutral value.
Never use a plug in a socket of a different colour or hour rating, even if it physically fits with force. The keying system exists to prevent dangerous incorrect connections.
Ensure the PE (earth) conductor is the last to be disconnected and the first to be reconnected in any plug or socket work. Loss of earth protection creates a lethal shock hazard.
This diagram is illustrative and reference-only. Verify all terminal assignments against the specific plug and socket manufacturer's documentation before wiring.

Tools needed

Calibrated voltage tester (CAT III or CAT IV)
Lockout/tagout kit
Insulated screwdrivers (flathead and Phillips)
Torque screwdriver (calibrated to plug terminal spec)
Wire strippers
Phase rotation meter or indicator
Insulation resistance tester (megohmmeter)

Common mistakes

Connecting L1, L2, L3 to incorrect terminals, causing motors to run in the wrong direction or creating phase-to-phase voltage imbalances.
Under-torquing terminal screws, which causes high-resistance arcing at the joint, overheating, and eventual terminal failure.
Clamping individual cores in the strain relief instead of the outer cable sheath, so mechanical stress is transferred directly to the terminal connections.
Using a 4-pin plug (without neutral) on equipment that requires neutral for control circuits, causing malfunction or damage.
Mixing old (red/yellow/blue) and new (brown/black/grey) colour-coded cables without clearly marking the interface — this has caused serious accidents during maintenance.

Troubleshooting

Motor runs in the wrong direction after wiring: Cause: Phase rotation L1-L2-L3 is reversed relative to what the motor requires. Fix: Isolate and lock out the circuit. Swap any two of the three line conductors (L1 and L2, or L2 and L3) at either the plug or the motor terminal box. Restore supply and verify rotation before coupling the load.
Plug or socket body runs hot: Cause: Terminal screws under-torqued, causing high contact resistance; conductor strands not fully inserted; or load current exceeds plug rating. Fix: Isolate the circuit. Open the plug body and inspect terminals for heat discolouration or arcing marks. Re-terminate with correctly stripped conductors and torque to specification. Verify load current with a clamp meter does not exceed the plug rating.
Equipment trips earth leakage device (RCD/GFCI) on connection: Cause: Insulation fault in the cable or equipment, or a ground fault in the wiring. Fix: Disconnect the load. Test insulation resistance of the cable alone — should exceed 1 MΩ between each conductor and earth. Then test the equipment separately. The fault is in whichever section fails the insulation test.

Frequently asked questions

What do the colours of IEC 60309 plugs indicate?

The plug body colour indicates voltage range: red for 380–415 V 3-phase, blue for 200–250 V (single or 3-phase), yellow for extra-low voltage. The clock-face hour position of the earth pin indicates frequency — for example, a red 6h plug is 380–415 V at 50 Hz. Never connect equipment to a socket of the wrong colour or hour rating.

What is the difference between a 4-pin and 5-pin IEC 60309 3-phase plug?

A 4-pin plug carries L1, L2, L3, and PE (earth) only — for 3-phase loads like motors and heaters that do not need a neutral. A 5-pin plug adds a neutral conductor (N), allowing single-phase loads within the same system or equipment with neutral-referenced control circuits. Check the equipment rating plate for whether neutral is required.

What conductor colours are used in a 3-phase IEC 60309 cable?

Under IEC 60446 and current European practice: L1 = Brown, L2 = Black, L3 = Grey, N = Blue, PE = Green/Yellow. Older UK installations may use Red/Yellow/Blue for phases and Black for neutral. Always check colour coding against the cable markings and local wiring regulations, as older cables use the legacy scheme.

Can I wire a 32A IEC 60309 plug myself?

In most jurisdictions, connecting industrial plugs and sockets on fixed installations requires a licensed or competent electrician. Some regions permit a competent person to replace like-for-like plug tops on flexible cords. Check your national regulations (BS 7671, NEC, AS/NZS 3000) and, if in doubt, have the work certified by a qualified electrician.

How do I confirm the correct phase rotation after wiring?

Phase rotation (sequence L1-L2-L3) determines the direction three-phase motors rotate. Use a calibrated phase rotation meter or sequence indicator connected to the socket to verify L1-L2-L3 follows the correct rotation for the connected equipment. Reversed phase sequence runs motors backwards, which can damage driven equipment.