Think of the controller as the power supply, the motor as the load, the motor as the actuator, and the controller needs to serve the motor. From a parameter perspective, the phase angle, current, power and voltage of the controller need to meet the requirements of the motor. For example, the power of the controller must be greater than or at least equal to the power of the motor, and the controller also has brushless and brushed controllers. If it is an electric vehicle, there are also options for asynchronous and synchronous motor control.
1. Parameters such as power and current must match
At present, DC motors are basically used to power electric vehicles on the market. DC motors are divided into brushed and brushless. If the motor is brushed, it relies on mechanical commutation. As long as the maximum voltage output by the controller and The maximum current should be greater than or equal to the rated voltage and rated current of the motor. Brushless motors are electronically commutated. The parameters of voltage and current must also be greater than or equal to the rated value of the motor, and the Hall signal configuration issue must be considered. The withstand voltage of the controller must of course be higher than the maximum voltage of the battery. The nominal voltage of the battery is not the maximum voltage. This should be noted. Generally, the maximum voltage is about 1.2 times the nominal voltage. For example, a 60-volt battery will be fully charged. The electricity may have gone to 72 volts. The power of the motor depends on the load and speed requirements of the load. These are not easy to calculate. Generally, the selection needs to be based on some empirical values. In some cases,
Consider that the national standard limit for electric bicycles is up to 400W and the maximum voltage is 48 volts.
The greater the power of the motor, the better the power of the car, but the faster the battery consumption, so the battery capacity must be increased to meet the requirements, and the specifications of the corresponding controller must also increase.
The higher the voltage of the motor, the higher the efficiency of the motor. However, if the voltage is too high, the insulation requirements for the wires and the controller are stricter. Battery management is also difficult, and safety problems are prone to occur. Generally, the control of two wheels is within It is relatively safe within 72 volts. As for those four-wheel electric vehicles, many are similar to industrial grade. The DC bus reaches more than 500 volts and the motor voltage is 380 volts. They often need to meet the IP67 design standard, otherwise they will be too dangerous to use.
2. Brushless motors need to consider the phase angle
The brushless motor commutates completely by sensing the rotor magnetic pole position through Hall signals. The three-position Hall will output two levels of 01, high and low. For example, 100 is a position of the stator and rotor time, and 000 is Another kind, after the three Halls are arranged and combined, there will be 36 signal states. The microcontroller needs to output different pulse voltages based on these signals to allow the controller to control the motor.
Among the 36 groups of signals, the actual values need to use the correct two groups, one is forward rotation and the other is reverse rotation. When the Hall is installed, the front and back are different, resulting in the so-called electrical vector difference of 60 degrees and 120 degrees. In this way, when selecting a controller, you need to choose the appropriate one based on this difference in angle. Of course, there are many controllers that can learn and judge by themselves. This phase sequence, but when you buy and use it, you should also pay attention to whether it is suitable.
In fact, there will be no difference between 60 degrees and 120 degrees in terms of control and use, as long as the software and hardware are designed in place. However, there may be differences because of production habits and maintenance.
Early controllers were often 60°, with three Halls placed in the same direction. This made production easier and would not cause errors. Nowadays, many small factories and low-power products still use 60%.
However, the 60-degree output signal has two special angle signals: 111 and 000. If the motor power is relatively large and the conduction speed is required to be fast, a conduction dead zone in the control may occur, causing damage to the driver. Therefore, in terms of reliability and safety design, 120° seems to be a little stronger, so many factories now use 120.
3. Consider economy and reliability
Of course, the greater the power of the controller, the better. However, if the motor power is relatively small and the battery capacity is insufficient, the larger the controller you buy, it will be a waste, resulting in a big horse and a small car. Moreover, electric cars should be as light as possible. , a controller that is too big may not be a good thing, generally 20% more power than the motor is enough.
The controller has overvoltage and undervoltage protection functions, which need to be configured taking into account the highest and lowest voltage values of the battery. Otherwise, the protection may occur before the battery is fully discharged, or the battery voltage may be too high, causing no output.
Reliability is of course crucial, and no one likes to have their bike abandoned halfway. If you have the conditions, of course you need to use water cooling. If you don't have the conditions, you should also consider the installation location to ensure the rationality of heat dissipation, or add some fans to cool down.