Hello everyone,
I am using the MP6532 (TSSOP) with Hall sensors and a 20 kHz PWM frequency. The PWM signal is generated by an MCU, which sends PWM and DIR signals to my board.
The MOSFETs I am using are 045N10N3, and each Rsense resistor has a value of 0.1 Ω (0R1).
The MCU firmware operates as follows: it starts by sending a 0% PWM duty cycle, then gradually increases the duty cycle with a ramp-up until reaching 100% speed. After that, the speed decreases with a ramp-down until the motor stops. The system then waits 2 seconds and repeats the cycle.
The motor rotates correctly, but a problem arises.
When the motor is stopped (while waiting to start rotating), I hold the shaft with my fingers. As soon as the motor begins to draw current, the motor does not rotate. I can easily prevent it from turning, which means the rotational force (mechanical torque) is extremely low.
I measured the current consumption by connecting a multimeter in series with the 48 V supply. When the motor reaches maximum speed, the multimeter reads 0.300 A.
I also connected a 100 µF / 63 V electrolytic capacitor in parallel with the 48 V supply.
The OCREF pin is connected to the VREG pin through a 100 kΩ resistor in order to disable the protection function.
Below are some technical specifications of the system:
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Supply voltage (power supply and motor): 48 VDC
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Motor power: 315 W
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Motor current (no load): 0.8 A
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Motor current (with load): 6 A
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Number of poles: 4
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Hall sensor pull-up resistors: 4.7 kΩ
Please help me understand why the torque is so low when the motor starts from standstill.
Also, please advise how to increase the starting torque.
Thank you in advance for your responses.