Terminal Identification

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The terminals on a single-phase motor have a standard identification method. The ends of the start and run windings are numbered to help one identify and locate them when one must install or troubleshoot the motors.

Terminal identification & color codes for single phase motors.
Above: Fig. 1: Terminal identification and color codes for single phase motors.

Fig. 1 shows the standard numbering method for a split-phase motor. In this figure two diagrams are presented to show an eight-lead and a four-lead motor.

In this figure the two windings are shown connected in parallel as they operate electrically. The run winding is shown in two sections. The numbering starts at the t of the diagram, with the terminals of the first section being numbered 1 and 2. The second section’s terminals are numbered 3 and 4. The start winding is also shown in two sections, with the terminals of the top section numbered 5 and 6, while the bottom terminals are marked 7 and 8.

The run and start winding terminals can also be identified by the amount of resistance each has. Since the start winding is made of many turns of very fine wire, its resistance will be much higher than that of the run winding. If the terminal identification is missing, one can use a continuity test to group the terminal leads into coils. Then by measuring their resistance, one can compare the readings. The highest readings will belong to the start windings, while the lower readings indicate that the winding is the run winding. This figure also shows a table with the color code for each of the motor terminal conductors for single-phase motors.

The color codes may be used if the terminal identification is not used. Note that some manufacturers identify their leads with terminal markers, so the colors of wires that are used in their motors have no meaning. It's also important to understand that some manufacturers don't adhere to the color codes so one must always confirm the terminal markings with an ohm test.

Single-Phase AC Motor: Stator

Rotor and End Plates