For applications where a reverse spin is not acceptable, the Initial Position Detection algorithm (IPD) function is an alternative way to initialize the motor. With the proper IPD setting, the motor startup is also faster. While this function is suitable for motors with high inertia, such as heavy blades (for example: a ceiling or appliance fan), it is not suitable for motors with low inertia, such as small blades (for example: a computer fan), because the current injection will cause the motor to shake, resulting in the IPD not being accurate.

In applications where the acoustic noise generated by IPD is not acceptable during startup, it is recommended to select Slow first cycle as the startup method.

Option 1: IPD

Step 1: If IPD is chosen as startup method, select IPD in the Motor startup option [MTR_STARTUP] in “Control Configuration – Motor Startup Stationary” tab in the GUI.

Step 2: Select the IPD Current threshold [IPD_CURR_THR]. IPD current threshold is selected based on the inductance saturation point of the motor. A higher current has better chance to accurately detect the initial position. However, higher current might result in rotor movement, vibration and noise. It is recommended to start with 50% of the rated current of the motor. If the motor startup is unsuccessful, then we recommend increasing the threshold till the motor starts up successfully. Note that the IPD current threshold should not be higher than the rated current of the motor. Use Equation 3 to choose the correct IPD_CURR_THR.

Step 3: Select IPD clock value [IPD_CLK_FREQ]. The IPD clock defines how fast the IPD pulses are applied. Higher inductance motors and higher current thresholds need a longer time to settle the current down, so we need set the clock at a slower time. However, a slower clock makes the IPD noise louder and last longer, so we suggest setting the clock as fast as possible as long as IPD current is able to settle down completely.

Looking at Figure 8, the current does not settle completely, which means the clock is too fast for this motor. This will result in IPD not being able to reliably identify the initial position of the motor.

Step 4: Select IPD Advance angle [IPD_ADV_ANGLE]. This decides how much angle to be added to IPD vector. To start with, choose smaller value to get smoother spin-up. Highest start up torque is achieved with 90-degree advance input.

Step 5: Select IPD Advance Angle [IPD_ADV_ANGLE]. It is recommended to Start with 90⁰ to get maximum startup torque. If there is sudden jerk observed during startup, then it is recommended to reduce the angle to 60⁰ or 30⁰ for a smoother startup.

Option 2: Slow first cycle

Follow below steps if Slow first cycle is chosen as the startup method.

Step 1: Select Slow first cycle in the Motor startup option [MTR_STARTUP] in “Control Configuration – Motor Startup Stationary” tab in the GUI.

Step 2: Select Align current threshold [ALIGN_CURR_THR]. Lower current threshold may lose synchronization of motor. Higher current may lead to sustained oscillations for high inertia motors, or sudden jerky motion for low inertia motors. It is recommended to start with 50% of the rated current of the motor. In applications where the startup torque is high, the motor might lose synchronization. In such applications, it is recommended to increase the current reference. In applications where, sustained oscillations or sudden jerks are observed, it is recommended to decrease the current threshold.

Step 3: Select Align current ramp rate [ALIGN_RAMP_RATE]. Current reference is ramped to avoid reverse rotation of the motor. Lower current ramp rate may lose synchronization of motor. A higher current ramp rate may lead to sustained oscillations for high inertia motors, or sudden jerking motion for low inertia motors. It is recommended to start with setting up the ramp time to 0.5 sec to ramp to rated current of the motor. In applications where the startup torque is high, the motor might lose synchronization. In such applications, it is recommended to increase the current ramp rate. In applications where, sustained oscillations or sudden jerks are observed, it is recommended to decrease the current ramp rate.

Step 4: Select Frequency of first cycle [SLOW_FIRST_CYC_FREQ]. Lower frequency may give a jerky motion at startup. Higher frequency may not be able to synchronize the motor. It is recommended to start with 20% of the maximum speed of the motor. In applications where the startup torque is high, the motor might lose synchronization. In such applications, it is recommended to decrease the frequency. In applications where jerky motions are observed, it is recommended to increase the frequency.