9 Leads Terminal Wiring Guide for Dual Voltage Star (Wye) Connected AC Induction Motor

It is of utmost importance to firstly understand the internal wiring configuration of a 9 leads AC induction motor before doing the actual wiring connection.  All 9 leads motors are most commonly made for dual voltage application, this means that the motor was manufactured specifically for dual voltage operation which can be connected in either 220 volts or 440 volts configuration.

There are two types of connection configuration for a 9 leads AC induction motor, they are either internally connected for star (wye) or delta configuration. To prevent burning the motor, make sure to firstly identify if the 9 leads motor is factory pre-configured in the star (wye) or delta configuration before attempting any wiring connection and installing power to run the motor.

To determine the internal wiring configuration of the motor, the best approach is to make use of an ohm meter to measure the continuity of the motor's internal coil winding through the wiring terminals accessible from the motor's terminal box. Before measuring the continuity of the motor's internal connection, make sure that all external wiring terminal of the motor is disconnected first to ensure accurate continuity readings.

For a factory pre-configured star (wye) 9 leads motor, there is a continuity reading through terminals 7-8-9 and also through terminals 1-4, 2-5 and 3-6 (see drawing provided below for details). Obtaining these continuity readings confirms that the motor is internally configured for a star (wye) connection.

The dual operational voltage rating values of the motor is determined from the motor's nameplate. A most commonly used example is a 9 leads motor intended for 220 and 440 volts operation. Each of these designated voltages requires different methodology of wiring connection in order to run the motor in either 220 or 440 volts operation.

Fig-1:  9 Leads 3 Phase High Volts Star (Wye) Connected Motor Configuration

To connect the motor to its rated high voltage configuration, Fig-1 above shows an electrical schematic diagram of a star (wye) configured 9 leads motor so connected for a 440 volts AC power supply. The 3 phase AC source line voltage L1 is connected to the motor terminal 1, line voltage L2 to motor terminal 2 and line voltage L3 to motor terminal 3, while also individually joining together motor terminals 4-7, 5-8 and 6-9 respectively (refer to above drawing).

Fig-2:  9 Leads 3 Phase Low Volts Star (Wye) Connected Motor Configuration

To connect the motor to its rated low voltage configuration, Fig-2 above shows an electrical schematic diagram of a star (wye) configured 9 leads motor so connected for a 220 volts AC power supply. The 3 phase AC source line voltage L1 is connected to the motor terminal 1 and 7, line voltage L2 to motor terminal 2 and 8, and line voltage L3 to motor terminal 3 and 9, while also joining together motor terminals 4-5-6 (refer to above drawing).

Another variation of wiring configuration for a 9 leads motor connection apart from the 9 leads star (wye) connection is the 9 leads delta wiring configuration.