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Testing BLDC motor's Phase Wiring - Hall Sensors and Wiring.

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    Testing BLDC motor's Phase Wiring - Hall Sensors and Wiring.

    Testing electrical components of a typical hub motor with a digital multi meter.

    Two major electrical systems need to be checked out in a typical BLDC hub motor. Take a few minuets and look over the wiring going into the motor for cuts, scrapes, missing insulation and other wiring issues that should be resolved first.

    1) The motor's 3 windings. (high voltage components)
    2) The motor's 3 hall sensors, (low voltage components) if present. If not, you will need a "sensor less" capable controller and skip these tests.

    Motor Winding Testing.

    With the 3 phase wire leads (heavy gauge wires) disconnected from everything, and not moving or turning the motor. Test resistance (ohms)between two phases at a time, and comparing all three phase combination's resistances.
    All three readings should match. Note that this is just a general check with a DMM. As the resistance readings are very low to be real accurate. It's not so much the reading, but if they all are comparable. Very easily can be much less than 1 ohm.
    Then check resistance between each phase wire at a time and a metal part of the motor. It should read infinity or open circuit. Nothing shorted or any resistance reading to ground. If so do not use motor until repairs (if possible) are made.

    Then tie two phase wires together in different combinations at a time for a total of three tests. At each combination, a similar magnetic resistance (also known a "cogging ') should be felt while trying to turn the wheel. With no resistance present when all wires are separated.
    Note: on a geared hub motor, wheel will have to be turned in reverse to engage the motor.

    And lastly, if your able to spin your motor with a drill at the same constant speed for all testing. Spin the motor up and first check for hot spots in the windings. Then compare the AC voltage outputs of all three combinations of phase wires. They should all be close to the same.

    Motor Hall Sensor Testing.

    In a BLDC motor that has hall sensors. The hall sensors are used to determine the position of the rotor for accurate sensor type controller operation. Each hall sensor has three wires and requires a voltage input (typically 5vdc) , 0vdc, (batt negative, or ground), with the last wire being output. This will bring the harness wires to a total of 5. (Typically, RED=5vdc+ ,BLACK=0vdc, and each of the last three are the outputs of there respective sensor.) When effected by the motor's magnet's gauss (positive and negative) passing by the sensor, it will switch output voltage from 5vdc to 0vdc. This voltage switching, at the correct time, and in the correct order is used by the controller.
    Note: Some motors may include a 6th wire in this bundle. Typically white in color and used to connect to an internal thermal sensor.

    For replacement a well known and often used hall sensor used in BLDC motors to determine rotor position would be the Honeywell SS41 series.
    Here is the data sheet for both the F & G models.

    1) Testing when connected to a working controller.

    See this tutorial...

    2) Bench testing not using a controller.

    As a controller provides a "pull up" resistor to the hall sensor circuit for proper switching between the two typical values. (5vdc and 0vdc) One will have to be supplied and added to the circuit when testing the motor by itself. And also providing an external 5vdc source. For this a USB type supply or rechargeable cell phone back-up battery works well. (3- 1.5vdc AA batteries is series... ETC.) Current or amperage requirements are low. (<25mAs...)

    See this tutorial...

    And this...

    After the motor's wiring and components have been verified as good. The motor's phase wiring to hall sensor locations need to be correctly identified and wired for the correct controller output.

    If you have a controller with "learning wires" or "auto configuration" by all means put it to use. As the controller will magically configure itself. If not, use this chart to successfully pair the hall sensors to their respective phase windings...

    Take it easy on the throttle till better results are obtained! (see Testing Recommendation box in the chart.)

    Last edited by Tommycat; 3 weeks ago.
    See my completed Magic Pie V5 rear hub motor E-Bike build HERE.