SLLU335A August   2021  – January 2022 MCF8316A

 

  1. 1Revision History
    1.     Trademarks
  2. 2Introduction
    1. 2.1 Hardware and GUI Setup
      1. 2.1.1 Jumper Configuration
      2. 2.1.2 External Connections
      3. 2.1.3 Connecting to the GUI
        1. 2.1.3.1 Connect to computer
        2. 2.1.3.2 Connect to the GUI
        3. 2.1.3.3 Verify Hardware Connection
  3. 3Essential Controls
    1. 3.1 Recommended Default Values
    2. 3.2 Device and Pin Configuration
      1. 3.2.1 Speed Input Mode
    3. 3.3 Control Configuration - Motor Parameters
      1. 3.3.1 Maximum Motor Electrical Speed (Hz)
    4. 3.4 Control configuration - Closed Loop
      1. 3.4.1 Current Limit for Torque PI Loop
    5. 3.5 Testing for Successful Startup into Closed Loop
    6. 3.6 Fault Handling
      1. 3.6.1 MPET IPD Fault [MPET_IPD_Fault]
      2. 3.6.2 MPET BEMF Fault [MPET_BEMF_Fault]
      3. 3.6.3 Abnormal BEMF Fault [ABN_BEMF]
      4. 3.6.4 Lock Current Limit [LOCK_LIMIT]
      5. 3.6.5 Hardware lock Current Limit [HW_LOCK_LIMIT]
      6. 3.6.6 No Motor Fault [NO_MTR]
  4. 4Basic Controls
    1. 4.1 Device and Pin Configuration
      1. 4.1.1 Power Saver or Sleep Mode for Battery Operated Applications
      2. 4.1.2 Direction and Brake Pin Override
    2. 4.2 System Level Configuration
      1. 4.2.1 Tracking Motor Speed Feedback in Real Time
      2. 4.2.2 Improving Acoustic Performance
      3. 4.2.3 Protecting the Power supply
      4. 4.2.4 Monitoring Power Supply Voltage Fluctuations for Normal Motor Operation
    3. 4.3 Control Configurations
      1. 4.3.1  Motor Parameter Estimation to Minimize Motor Parameter Variation Effects
      2. 4.3.2  Initial Speed Detection of the Motor for Reliable Motor Resynchronization
      3. 4.3.3  Unidirectional Motor Drive Detecting Backward Spin
      4. 4.3.4  Preventing Back Spin of Rotor During Startup
      5. 4.3.5  Faster Startup Timing
      6. 4.3.6  Gradual and Smooth Start up Motion
      7. 4.3.7  Improving Speed Regulation
      8. 4.3.8  Stopping Motor Quickly
      9. 4.3.9  Preventing Supply Voltage Overshoot During Motor Stop.
      10. 4.3.10 Protecting Against Rotor Lock or Stall Condition
      11. 4.3.11 Maximizing Thermal Efficiency and Increasing Thermal Performance
      12. 4.3.12 Mitigating Electromagnetic Interference (EMI)
      13. 4.3.13 Faster deceleration

4.2.2 Improving Acoustic Performance

Acoustics is audible noise contributed by motor commutation and harmonic frequencies in motor drives. Stator excitation in motor drivers can generate mechanical resonance at audible frequency ranges leading to audible noise. Improving acoustic performance is important for applications that require quiet operation. Any distortion in phase current can translate to audible noise. Phase current distortion can be due to dead time, PWM modulation scheme or low MOSFET slew rate.

Step 1: Configure PWM Modulation scheme [PWM_MOD] to “Continuous Space Vector Modulation”.

Note:

  1. In Continuous Space vector modulation, phase current waveform shaping will be better but the MOSFET switching losses will be higher.

  2. In Discontinuous Space vector modulation, MOSFET switching losses will be lower. However, we can expect phase current distortion for low inductance motors.

Step 2: Enable Dead time compensation [DEADTIME_COMP_EN]

For speeds above 125 Hz, decrease MCC dead time [MCC_DEAD_TIME] till the phase current distortion gets better.

Note:

Decreasing the dead time might trigger Hardware lock detection current limit fault [HW_LOCK_ILIMIT]. If this fault gets triggered, increase the dead time.

Figure 4-1 shows the phase current waveform when dead time compensation is disabled. Fundamental frequency of phase current is 40 Hz. Fast Fourier transform (FFT) of phase current plot shows harmonics at 160 Hz and 220 Hz. Figure 4-2 shows the phase current waveform when dead time compensation is enabled. Phase current looks more sinusoidal and the FFT of phase current plot does not have any harmonics.
Figure 4-1 Phase current and FFT - Dead time compensation disabled
Figure 4-2 Phase current and FFT - Dead time compensation enabled