Board application setup PMSM

The board application setup for the 3-phase PMSM FOC example incorporates the following:

Table 1: Hardware components list with parts order number

_{Note 1: Please note that one NXHX-DH adapter is included in each NXHX 90-MC board delivery box.}

^{Note 2: Alternative to the ECl-42.20-K1-B00 with IQ-Encoder.}

As illustrated in Figure 1, the motor supply is at the same time the power supply for the NXHX 90-MC board. The integrated DC/DC converter of the 3-phase gate driver, with a wide voltage input range, generates the 3.3V single supply for the netX 90. Depending on the motor of choice, the power inverter is designed to enable a DC board supply for a 3-phase BLDC/PMSM of +12V, 24V or 36V.

Hilscher uses as reference in this particular case a 24V/2.5A servomotor from ebm-past, which serves as example for a specific PMSM with integrated digital hall sensors and optional quadrature encoder. The NXHX-DH adapter as depicted provides the power supply for integrated motor electronics and converts the position and speed feedback signals to 3.3V inputs for the netX 90.

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Figure 1: NXHX 90-MC board application with NXHX-DH adapter

The NXHX-DH adapter mirrors the connectors X901 (digital hall sensors), J3, J4 (quadrature encoder interface) and J7 (supply header) of the NXHX 90-MC board. Interconnect X901, J3, J4 and J7 of both boards by plugging the NXHX-DH adapter onto the NXHX 90-MC board. Interconnect the ECl-42.20-K1-B00 and the EC-i 30 Ø30 mm with the NXHX-DH adapter and the NXHX 90-MC board as follows:

Table 2: Interconnection of the halls and encoder wires

Table 3: Interconnection of the 3-phase PMSM winding wires

The netX 90 requires a hardware configuration, which is a binary file with the extension HWC that is stored on-chip and contains the user's pin assignment. This file is generated using the hardware configuration tool, which is integrated into the netX Studio CDT. Figure 2 shows the GUI of the hardware configuration tool with the configured pin assignment for the 3-phase PMSM FOC example with digital hall sensors and quadrature encoder (see Figure 1). The stored HWC file is processed by the internal ROM code and ensures that the pinout of the netX 90 is configured before any of the software is started.

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Figure 2: Pin assignment for the 3-phase PMSM FOC example

The inner loop of the FOC requires the assignment of the MPWM pins for the three half bridges and the MADC pins for the three current shunt amplifiers. The configuration interface of the 3-phase gate driver is connected to SPI1_APP. PIO_APP12 is the chip select line for the SPI and PIO_APP8 is the enable signal for the DRV8323R. The outer loop of the FOC requires the assignment of the GPIO[0:2] pins for digital hall sensors and the MENC0 pins for the quadrature encoder. The 3-phase PMSM FOC example enables determining the rotor angular position in either way.

Table 4: MADC unit and channel matrix of the NXHX 90-MC board

During braking, electrical energy is may fed back into the DC-link through the self-induction of the motor. Without a power supply capable of regenerative feedback, the braking power can cause the DC-link voltage to increase. To prevent damage from overvoltage, it may be necessary to dissipate excess energy as heat, depending on the level of braking power. The brake chopper dissipates this excess energy via a resistor into heat if an adjustable voltage value is exceeded.

The adjustable voltage for the brake chopper is monitored using VSENVM. The brake chopper is not active by default in the source code because the voltage value depends on the power supply, motor, etc. If required, an external braking resistor must be connected to J6. The transistor is controlled by the mpwm_bc or mpwm_bc_s. The shadow register value is automatically adopted in the grid of the MPWM frequency for the current control.