The Hall sensors inside the motor are positioned 120° apart. As the magnetic rotor passes by these sensors, they are activated every 60° within one electrical cycle. This means there are six Hall transitions for each electrical cycle as the rotor follows the stator’s magnetic field.
Based on the arrangement of the Hall sensors in the motor, the following six states will occur:
| Hall A | Hall B | Hall C | Hall status |
| 1 | 0 | 0 | 1 |
| 1 | 1 | 0 | 3 |
| 0 | 1 | 0 | 2 |
| 0 | 1 | 1 | 6 |
| 0 | 0 | 1 | 4 |
| 1 | 0 | 1 | 5 |
The Hall status represents the binary-to-decimal conversion of the Hall sensor signals. For example, 001 equals 1, and 100 equals 4. In this scheme, Hall C is the most significant bit (MSB).
The following criteria should be checked to validate the proper operation of the Hall sensors:
- The duration of each Hall state is consistent.
- All Hall transitions from 1 to 6 are observed.
- Hall statuses 0 and 7 are absent, as they are invalid.
- The signal sequence is one of the following, depending on motor direction: 1-3-2-6-4-5 or 5-4-6-2-3-1.
Different sensor failure modes can have varying impacts on motor rotation. For example, if the sensors are misaligned—resulting in unequal Hall state durations—the motor current may become unstable. If one of the Hall signals is missing, the Hall status will not cycle through all states from 1 to 6, and the motor will likely be unable to rotate at all.
example of misaligned Hall sensors
Example of Hall B signal missing
The Hall state can be monitored in the Diagnostics tab during motor/sensor setup.
If one or more sensor signals are missing, it is necessary to determine whether the failure lies in the sensor or in the motor drive itself.
To verify the motor drive inputs, perform the following:
Disconnect the sensor and use a wire to connect each sensor input (A, B, and C) to the ground pin of the sensor terminal. Each time an input is connected to ground, its state should change from 1 to 0. The reason the idle state of the input is reported as 1 is due to the motor drive’s internal pull-up resistor.
If the state of all inputs is changing as expected, then the motor drive inputs are functional and the failure lies withiin the sensor.
