Pure electric tractor - ① Overview

In the past two years, the sales of pure electric heavy-duty trucks have rapidly increased, and their application scenarios are mainly focused on short distance fixed route transportation, such as steel mills, docks, and environmental sanitation. As the capacity of power batteries continues to increase, pure electric heavy-duty trucks will adapt to a wider range of operating conditions. Below is an introduction to the Auman pure electric tractor.

Power Chain:

The power chain composition of a pure electric heavy-duty truck is shown in the figure. The powertrain consisting of an electric motor and a gearbox replaces the engine and gearbox of a fuel powered vehicle, while the transmission shaft and drive axle behind the gearbox are not much different from those of a fuel powered vehicle. This power chain arrangement evolved from gasoline vehicles.

Power battery:

The power battery is the energy source of an electric car, acting like the fuel tank of a gasoline car. At present, the power battery has expanded from the initial single specification of 282kWh to a series of products such as 350kWh, 423kWh, and 512kWh. Pure electric heavy-duty trucks are equipped with DC high-voltage charging ports for battery replenishment. The power battery box of the battery swapping car can be easily lifted and replaced as a whole, saving charging waiting time and improving work efficiency.

The remaining state of charge (SOC) of a power battery is one of the important parameters of the battery. When the battery level is below 20%, the instrument panel will light up an alarm light to prompt the user to charge (replace) the battery; If the battery level is below 15%, the alarm light will light up and the instrument buzzer will sound, at which point the motor will begin to limit the output torque.

Another important parameter of power batteries is battery temperature. The most suitable temperature range for battery charging and discharging is 25 ℃~45 ℃. In order to maintain the battery in the appropriate temperature range, the battery box is equipped with an electric heating system and a water and refrigerant cooling system, which are collectively referred to as the battery thermal management system.

Battery energy recovery: The driving motor of the tram instantly becomes a generator during energy recovery, which is a magical process. When braking, the chassis reverse drag motor rotor shaft (gearbox shaft) rotates, and the motor stator coil outputs three-phase AC current, which is then rectified by IGBT and outputs high-voltage DC power to charge the power battery. During this process, mechanical energy is converted into electrical energy, while generating braking effect.

The right handle of the combination switch is the auxiliary brake switch, just like the hydraulic buffer switch of a gasoline truck, which also has five gears to choose from: constant speed, 1, 2, 3, and 4. The auxiliary braking energy recovery needs to meet the condition that the SOC is below 95% in order to start normally; If the power battery is fully charged, even if the auxiliary braking switch is turned on, the energy recovery braking will not work.

The EBI switch installed on the tram is related to energy recovery. When this switch is pressed, each time the foot brake is applied, the motor recovery brake will bear a portion of the braking load. As long as the wheels do not slip during braking, this switch can remain pressed (turned on) to improve energy recovery rate. In extreme road conditions such as icy and muddy roads, to prevent wheel slippage during braking, the EBI switch needs to be turned off; Be cautious when using the EBI function on rainy days. When braking with the EBI switch on, pay attention to whether the wheels have a tendency to slip. If a slip tendency is found, turn off the EBI switch.

electric machinery:

The driving motor is a three-phase synchronous motor, and the biggest feature of synchronous motors is the presence of a rotary sensor, which is used to determine the real-time position of the motor rotor to meet the requirements of synchronous control. After the rotary transformer malfunctions, the motor will not be able to work.

In addition, the motor is equipped with a temperature sensor to monitor the motor temperature. If the motor temperature exceeds a certain value (135 ℃), the motor will enter overheat protection mode and limit torque output.

In order to maintain a suitable working temperature for the motor, it has a specialized cooling system consisting of an electric water pump, fan, radiator, and pipeline, which dissipates excess heat into the atmosphere.

Motor controller:

The motor controller is responsible for motor control. The motor controller is located between the battery and the motor, and has an important electrical component IGBT inside, which plays a dual role as an inverter and rectifier. When the motor is driven, IGBT converts the DC power of the power battery into AC power to drive the motor operation; When the motor recovers the brake, IGBT rectifies the AC power generated by the motor into DC power to charge the power battery. Due to the high working current and heat load of IGBT, the cooling fluid of the motor cooling system also flows through the motor controller to dissipate heat.

The motor controller of the Ouman electric tractor is integrated into the multi in one controller PEU.