Step 6: Set bus current limit during active braking [ACTIVE_BRAKE_CURRENT_LIMIT]
Note
Follow the below recommendations if the motor fails to resynchronize in reverse direction.
1. Increase the reverse deceleration speed threshold to transition to open loop
2. Enable Open loop reverse drive configuration [REV_DRV_CONFIG]
3. Increase the Reverse Drive Open Loop Current Reference
[REV_DRV_OPEN_LOOP_CURRENT]
4. Decrease open loop acceleration coefficient A1 and A2 during reverse drive
5. If the device triggers Lock current limit [LOCK_LIMIT], then increase the open loop current limit
during speed reversal [REV_DRV_OPEN_LOOP_CURRENT]
4.3.4 Preventing Back Spin of Rotor During Startup
For applications where a reverse spin is not acceptable, the Initial Position Detection algorithm (IPD) function is
an alternative way to start up the motor. With the proper IPD setting, the motor startup can be faster than using
align. 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 (“chirp”) 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.
Step 3: Select IPD clock value [IPD_CLK_FREQ]. 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 it lasts longer, so we
suggest setting the clock as fast as possible as long as IPD current is able to settle down completely.
Note
Device triggers IPD timeout faults [IPD_T1_FAULT] and [IPD_T2_FAULT] for motors with very high
inductance, or if the motor is not connected. If this fault gets triggered, it is recommended to check if
motor is connected to the device. If the fault still persists, it is recommended to set the IPD release
mode [IPD_RLS_MODE] to Tri-state if any overshoot in DC bus voltage is acceptable.
Device triggers IPD Frequency fault [IPD_FREQ_FAULT] if the IPD clock frequency is set too high. If
this fault gets triggered, it is recommended to decrease the IPD Clock value [IPD_CLK_FREQ].
Step 4: 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.
Basic Controls
SLLU335A – AUGUST 2021 – REVISED JANUARY 2022
MCF8316A Tuning Guide
17
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