Introduction to the key components of motor controllers
As a core component of the electric vehicle powertrain, the design and function of the motor controller rely on the coordinated work of a series of key components.
The following are the main components in the motor controller and their functions:
1. DC busbar: The DC busbar is a conductor with high conductivity, low resistance and good heat dissipation characteristics that connects the battery pack and the motor controller. It ensures that DC power is transmitted from the battery pack to the motor controller without loss or with low loss.
2. Inverter structure: The core of the motor controller is a three-phase full-bridge inverter, which is responsible for converting DC power into three-phase AC power to drive the AC motor. The inverter consists of multiple power semiconductor switches, which can achieve precise control of the motor by precisely controlling the opening and closing of these switches.
3. Electromagnetic interference (EMI) suppression: The electromagnetic interference generated by the inverter during operation is reduced by filtering components such as X capacitors and Y capacitors. X capacitors and Y capacitors are used for filtering between power lines and between power lines and ground, respectively. Film capacitors or ceramic capacitors are usually used and must meet specific safety standards.
4. Control circuit: The control circuit is the brain of the motor controller, responsible for signal acquisition and control algorithm implementation. It usually includes a microcontroller or digital signal processor (DSP) and related support circuits, with the core being the power module, which is responsible for power conversion.
5. Drive circuit: The drive circuit provides drive signals to the switching devices in the power module to ensure that they can switch accurately and quickly.
6. Heat sink: The heat sink is used to dissipate the heat generated by the power module and keep key components running at a suitable operating temperature.
7. Signal acquisition: The motor controller needs to collect three-phase current signals and position signals at the motor end to achieve real-time monitoring of the motor status. This usually involves the use of hardware such as current sensors.
8. AC output copper bus: The connection between the motor controller and the motor may use an AC output copper bus to transmit three-phase AC power. The copper bus design needs to consider low resistance and high current carrying capacity.
9. Resolver sensor interface: The position signal of the motor is usually provided by the resolver sensor, which needs to be connected to the corresponding interface of the motor controller.
10. Current sensor integration: The current sensor is generally integrated inside the motor controller to measure the current of the motor. Hall effect sensors or hollow perforated sensors can be used.
The collaborative work of these components ensures that the motor controller can achieve precise control of the electric vehicle motor while ensuring the safety and reliability of the system.
MCU is mainly composed of the following modules:
1. Microcontroller: The core function of the microcontroller is to control the voltage source inverter (VSI) to convert the power received from the battery into the required form of power. It receives the driver's throttle signal as the main control input and controls the speed and torque by adjusting the duty cycle of the pulse width modulation (PWM) pulse. The field vector control (FOC) implemented in the microcontroller ensures efficient and fast motor control.
2. Voltage Source Inverter (VSI): VSI is responsible for converting DC power to AC power to drive the motor. Six MOSFETs are usually used to implement VSI, and sometimes parallel combinations of MOSFETs are used to increase current capacity.
3. Phase Current Sensing: Hall effect-based current sensors are used to sense the phase current of the motor to ensure precise control. Two current sensors are usually used to sense two phase currents, and the third phase current is derived from these two.
4. Power Supply: The MCU's built-in sensors require appropriate power supply. In addition, the microcontroller, motor temperature sensor, and position feedback sensor also require different levels of power supply. The power supply section converts the fixed DC voltage into the required different levels of voltage.
5. Gate Driver: The gate driver circuit is used to amplify the voltage level of the PWM pulses generated by the microcontroller to ensure effective signal transmission.
6. CAN Transceiver: The CAN transceiver is used to drive and detect data transmitted over the CAN bus. It converts the single-ended logic used by the controller into a differential signal transmitted on the CAN bus.
7. Position Feedback Sensor: These sensors provide position information of the motor rotor and are essential for achieving accurate vector control. Encoders or resolver sensors are usually used to provide these feedback signals.
8. Temperature Sensor: The temperature sensor is used to monitor the temperature of the motor and controller to ensure safe operation of the system and prevent overheating.
The collaborative work of these modules ensures that the motor controller can control the motor efficiently and accurately while ensuring the stability and safety of the system.
