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Matching of Main Drive Motor Controller and Selection

Controller and drive motor and even the whole vehicle mainly includes power performance, cooling system, mechanical and electrical interface, control performance and software function matching.

1. Power performance matching The drive motor of pure electric vehicle requires torque to be generated at all speeds. The following picture shows the speed-torque curve of the vehicle drive motor. The drive motor requires constant torque characteristics at medium speeds below, and constant power characteristics at medium to high speeds. As shown in the following, the combination of torque and speed determines the operation of the motor, slope start, high-speed cruise and other different states, the driving state of the car will change greatly.

The outer characteristic curve shown is the maximum torque that the motor can output at that speed, and the driving motor operates over the entire area covered by the curve. The following picture shows an example of monitoring the actual driving status.

The peak torque of the drive motor can be set according to the climbing performance, the peak power can be determined according to the acceleration performance (the output power time can be determined according to the vehicle acceleration time target value, generally set to 10 to 60s), the rated power can be set by high-speed cruising speed and continuous climbing performance.

When matching the main drive motor controller to the drive motor, it is important to ensure that the power performance of the drive motor is matched. The matching of the main drive motor controller with the main performance parameters of the drive motor can be referred to tables.

2. Cooling system matching The cooling system matching of the main drive motor controller needs to consider the cooling mode of the drive motor and the cooling system of the whole vehicle.

1) In order to simplify the vehicle cooling system, the main drive motor controller is cooled in the same way as the matching drive motor. For example, when the motor is naturally cooled, the motor controller uses natural cooling or forced air cooling; When the motor is water-cooled, the motor controller also uses water-cooled; When the motor is oil-cooled, the controller is generally water-cooled because the cooling efficiency is higher.

2) Because the coolant path generally connects the drive motor in series with the motor controller, the diameter of the water port between the controller and the motor must be the same. 3) Because the temperature resistance of the controller is lower than that of the drive motor, the coolant passes through the controller and then through the drive motor.

4) In addition to the relevant dimensions of the controller coolant channel, the pressure flow characteristics of the coolant channel (Figure 1 ) need to be provided for the design of the vehicle cooling system. 5) For a more detailed vehicle cooling system design, it is also necessary to provide loss data for the drive motor and motor controller at various operating points, which can be calculated from the efficiency MAP diagram.

Figure 1

3. The mechanical and electrical interfaces match

The mechanical installation and electrical connection of the main drive motor controller need to take into account the characteristics and requirements of the vehicle and other components connected to it.

4. Control performance matching

In general, the basic control performance requirements of the main drive motor controller are shown in the following Table.

5. Software features match

As a common requirement for the controller, the main drive motor controller also needs to have software-related functions such as diagnostics (UDS), bootloader, calibration, etc.

For different vehicle design requirements, there may be more functional requirements for the main drive motor controller, such as high-voltage interlocking function, CAN wake-up function, anti-slip slope function, active damping function, active short-circuit function, etc.

1. Power Semiconductor Device Selection The main drive motor controller of an electric vehicle is based on the full bridge.

2. Support capacitor selection

Support capacitors are important components of the power circuit in the main drive motor controller, and also occupy a larger volume, whose function is filtering and energy storage. There are two main types of support capacitors in the main drive motor controller, electrolytic capacitors and thin film capacitors.

The selection of support capacitors mainly considers the following aspects

1. Rated voltage

2. Nominal power capacity

3. Ripple current

4. life span

3. Microcontroller selection

Microcontroller is the center of the whole main drive motor controller, based on the detection of the status information of external hardware platform and control object (motor), through various algorithms to make decisions, drive power semiconductor devices and the entire hardware platform, and then realize the control object fast, accurate and stable control.

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