3-Phase Motor Symbol

The 3-Phase Motor schematic symbol. Standard-specific details are listed below where available.

Definition: The 3-Phase Motor symbol represents a three-phase AC induction or synchronous motor, depicted in IEC 60617-06 as a circle containing the letter M annotated '3~', with three supply terminals labelled U, V, and W, used in industrial wiring diagrams for pumps, compressors, conveyors, and other three-phase motor-driven loads.

Also known as: three-phase motor, 3-phase AC motor, three-phase induction motor, squirrel cage motor symbol, M 3~ symbol, asynchronous motor.

What the 3-Phase Motor symbol means

The 3-Phase Motor symbol in a wiring diagram indicates that the load is a three-phase electric motor requiring three AC line conductors (U, V, W) and typically a separate earth/ground connection. Three-phase motors are the workhorses of industrial and commercial power systems, offering higher efficiency, greater starting torque, and smoother operation than equivalent single-phase types.

The symbol communicates that the motor requires balanced three-phase power at the correct voltage and frequency, that it must be protected against overcurrent and phase-loss conditions, and that its direction of rotation can be reversed by swapping any two of the three supply phases. In motor control diagrams, the 3-Phase Motor symbol is always shown connected through a contactor and overload relay.

How to identify the 3-Phase Motor symbol

The 3-Phase Motor symbol is a circle with the letter M (and often '3~' or 'M3') inside. Three terminals emerge from the top of the circle, labelled U (left), V (centre), and W (right), representing the three AC phases. Some drawings include a fourth terminal for the earth/PE connection at the bottom of the circle. The annotation '3~' distinguishes this symbol from single-phase (1~) and DC motor symbols.

Function and usage boundary

A three-phase AC motor converts three-phase electrical energy into mechanical rotation. The three-phase supply creates a rotating magnetic field in the stator at synchronous speed (n_s = 120f/P, where f is frequency and P is number of poles), inducing currents in the rotor that produce torque. Squirrel-cage induction motors run slightly below synchronous speed (slip ≈ 2–5%); synchronous motors run at exactly synchronous speed. The motor is started direct-on-line (DOL), star-delta, or via a variable frequency drive (VFD) or soft starter to limit inrush current.

Standards: IEC vs ANSI

IEC 60617	IEC 60617-06 defines the three-phase motor as a circle with M inside, annotated '3~' for three-phase AC. IEC 60034-1 governs ratings and performance of rotating electrical machines; IEC 60034-5 defines degrees of protection (IP ratings). Terminal labelling U, V, W follows IEC 60034-8.
ANSI/IEEE 315	ANSI Y32.2 / IEEE 315-1975 uses the same circle-M symbol for a general motor. Three-phase type is indicated by labelling terminal connections with A1/A2/A3 or T1/T2/T3 (per NEMA MG 1 conventions) rather than U/V/W, and by the three-phase annotation in the title block.
Key difference	IEC 60617 uses terminal labels U, V, W and the '3~' annotation inside the circle. ANSI/NEMA uses terminal labels T1, T2, T3 (or L1, L2, L3 at the supply side) and does not use the '3~' annotation; both use the identical circle-M glyph.

The displayed SVG is the live editor implementation, not a licensed reproduction or certification of an IEC or IEEE database glyph. Verify the exact official entry and project edition before issuing work.

Logical terminals

Logical ID	Editor terminal name
u	U
v	V
w	W

Where the 3-Phase Motor symbol is used

Industrial pumps and compressors: three-phase motors drive centrifugal pumps, screw compressors, and vacuum pumps in process plants
Conveyor and material handling systems: motor control diagrams show three-phase motors driving conveyor belts, hoists, and cranes
HVAC chillers and large air handling units: three-phase induction motors power commercial chiller compressors and large fan coil units
Machine tools: CNC mills, lathes, and grinding machines use three-phase motors for spindle and axis drives
Star-delta and soft-start motor control circuits: the 3-phase motor symbol appears as the load in DOL, star-delta, and VFD drive diagrams
Water treatment facilities: three-phase motors drive aerators, mixers, and centrifuges in industrial water systems

Key facts

The 3-Phase Motor symbol is a circle with M and '3~' inside, with three supply terminals U, V, and W per IEC 60617-06 and IEC 60034-8.
The standard reference designator for any motor is M (e.g. M1); three-phase type is identified by the '3~' annotation or three terminal connections.
Motor rotation direction reverses when any two of the three phase connections (U, V, W) are swapped — a fundamental property shown by phase-reversal wiring in motor control diagrams.
IEC efficiency classes IE1 (standard) through IE5 (ultra-premium) are defined in IEC 60034-30-1; IE3 is mandatory for many motor applications in the EU under Regulation (EU) 2019/1781.
Synchronous speed is calculated as n_s = 120f/P (rpm), where f is the supply frequency in Hz and P is the number of motor poles; a 4-pole motor on 50 Hz runs at 1500 rpm synchronous speed.
Starting inrush current for a DOL-started three-phase induction motor is typically 5–8 times full-load current; star-delta starting reduces this to approximately one-third.
The 3-phase motor symbol always appears in wiring diagrams with a protection device: a motor protection circuit breaker (MPCB), a thermal overload relay, or a fuse set per IEC 60364-5-54.

Diagrams that use this symbol

Frequently asked questions

What does the 3-phase motor symbol look like?

The 3-phase motor symbol is a circle with the letter M inside, often annotated '3~'. Three terminals (U, V, W) emerge from the top of the circle representing the three AC supply phases. IEC drawings use U/V/W labelling; NEMA/ANSI drawings use T1/T2/T3.

What does the three-phase motor symbol mean in a wiring diagram?

The three-phase motor symbol means the circuit includes an AC motor powered by a balanced three-phase supply. It indicates the motor converts three-phase electrical energy into mechanical rotation and requires a contactor, overload relay, and appropriate cable sizing.

What is the difference between single-phase and three-phase motor symbols?

The single-phase motor symbol (circle-M) has two terminals (Line, Neutral) and is annotated '1~'. The three-phase motor symbol has three terminals (U, V, W) and is annotated '3~'. Both use a circle-M glyph; the terminal count and phase annotation distinguish them.

What are the terminal labels on a three-phase motor?

Per IEC 60034-8, three-phase motor terminals are labelled U, V, W (supply side) and U1/U2, V1/V2, W1/W2 for dual-voltage winding ends. NEMA/ANSI practice uses T1, T2, T3 for the motor terminals and L1, L2, L3 for the supply conductors.

How do you reverse a three-phase motor?

A three-phase motor's rotation reverses when any two of the three supply phase connections are swapped (e.g. swap U and W while leaving V connected). This is shown in wiring diagrams by a reversing contactor that swaps two phases when the reverse command is given.

What standard defines the three-phase motor symbol?

The three-phase motor symbol is defined in IEC 60617-06 for the general motor circle-M glyph and IEC 60034-8 for terminal labelling (U, V, W). The equivalent ANSI reference is ANSI Y32.2 / IEEE 315-1975.

What protection devices are used with a three-phase motor symbol?

In wiring diagrams, the three-phase motor symbol is always paired with a motor protection circuit breaker (MPCB) or motor protection combination (MPC) and a thermal overload relay or electronic motor protection relay, all shown upstream of the U, V, W terminals.

Related symbols

Physical breadboard, PCB, and panel mapping

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