Hi team,
Here's some issue from the customer may need your help:
Issue 1: The MCT8316ZT has a Hall sensor interface, how fast can they detect a Hall model? Or how fast can the MCT8316ZT control BLDC motors?
The customer intends to control a MAXON BLDC motor bank, please see attached:
The component consists of BLDC motor + decelerator + photoencoder with a 57:1 deceleration ratio.
As shown above, the maximum continuous operating speed of the component is 191 RPM at the operating point indicated in the figure, so the motor speed is 191 x 57 = 10887 RPM The motor is a 1-pair motor, At 10887 RPM, there will be ( 10887 / 60 ) x 6 = 1088.7 per second equal to approximately 1089 Hall states. That is, the phase change interval (duration of each Hall state) is 1 / 1089 = 0.000918S = 918uS.
According to the section 8.3.15 in the MCT8316Z Data Manual:
The 0-to-t1 time is 918 uS and the t1-to-t2 time is 918 uS, which means the period of the FGOUT signal is 918 uS x 2. The frequency is approximately 545 Mz The frequency of the Hall signal is one-third of the frequency of the FGOUT signal, that is, 545 / 3 is approximately 182 Hz.
Are the above process correct?
Issue 2: How does the MCT8316ZT control the motor speed?
According to the data sheet, the PWM signal frequency of the hardware interface can be up to 200 KHz, which is the PWM switching frequency of the three-phase bridge.
Can the motor speed be controlled without adjusting the PWM signal duty cycle of the hardware interface? The output motor speed can be calculated from the FGOUT signal, a PI controller is created on software, and the PWM signal duty cycle of the hardware interface is dynamically adjusted with given and feedback speed calculated from FGOUT to achieve closed loop control of the speed?
So the MCT8316ZT can only do speed closed loop control? Because the bus current, the phase current, is not derived, and the chip can only do current limiting protection through ILIM.
Could you help check this case? Thanks.
Best Regards,
Cherry
