Three-Phase 75 kW Brushless Direct Current Motor for Electric Vehicles: Different Power Stage Design, Calculation of Losses, Cooling Techniques, and Comparison

1. Overview:

  • Title: Three-Phase 75 kW Brushless Direct Current Motor for Electric Vehicles: Different Power Stage Design, Calculation of Losses, Cooling Techniques, and Comparison
  • Authors: Ali Bahadir, Omer Aydogdu, Elif Bahadir
  • Year of Publication: 2024
  • Journal/Conference: Applied Sciences
  • Keywords: brushless DC motor, electric vehicles (EV), power stage, cooling system, losses

2. Research Background:

The increasing need to reduce CO2 and SO2 emissions due to climate change necessitates improvements in electric vehicle efficiency. While Brushless Direct Current (BLDC) motors are widely used in EVs due to their high power density, efficiency, and reliability, their operational lifespan is limited by high internal heat generation and inefficient heat dissipation. Therefore, research focusing on reducing electric motor losses and enhancing efficiency is crucial. Existing studies often focus solely on battery or motor cooling, neglecting the energy consumption of the cooling system itself.

3. Research Objectives and Questions:

  • Research Objective: To enhance the efficiency of electric vehicles by designing, calculating losses for, and comparing three different power stage designs and cooling systems (air cooling, fan-assisted air cooling, and liquid cooling) for a 75 kW BLDC motor.
  • Key Research Questions: How can the performance of three different power stage designs and cooling systems be compared? How can the efficiency and losses of each cooling system be quantified?
  • Research Hypothesis: The liquid cooling system will be more efficient than air cooling and fan-assisted air cooling systems.
Figure 16. DC-Bus IGBT heatsink and capacitance.
Figure 16. DC-Bus IGBT heatsink and capacitance.

4. Research Methodology:

  • Research Design: An electric vehicle model was built using MATLAB/Simulink. Three different power stage designs for a 75 kW BLDC motor were developed. Three different cooling systems were designed and their performance compared.
  • Data Collection Methods: Data was collected through simulation and experimentation. IGBT datasheets were used for loss calculations. Cooling system performance was evaluated through temperature measurements.
  • Analysis Methods: Loss calculations involved separately calculating switching and conduction losses and then summing them. Cooling system performance comparisons were based on temperature and efficiency.
  • Research Subjects and Scope: The study focused on three power stage designs and three cooling systems (air cooling, fan-assisted air cooling, and liquid cooling) for a 75 kW BLDC motor.

5. Main Research Findings:

  • Key Findings: The liquid cooling system proved to be the most efficient, followed by fan-assisted air cooling, and then air cooling. The spacing between IGBT modules significantly impacted thermal resistance.
  • Quantitative/Qualitative Analysis Results: Total losses for the three power systems were calculated to be approximately 2.3 kW, resulting in a system efficiency of about 97%. The liquid cooling system maintained an outlet temperature of 20.5 °C, removing 4.5 °C from the system. Without cooling, IGBT temperatures reached 96 °C, but with 20mm spacing, this reduced to 90 °C.
  • Data Interpretation: Efficient heat removal through the liquid cooling system lowered system temperatures and improved efficiency. IGBT module spacing significantly impacts heat transfer, necessitating optimization. The sandwich busbar design effectively reduced parasitic inductance and system size.
  • Figure List and Description: Figures in the paper visually represent the electric vehicle model, power stage designs, cooling system designs, loss calculations, and experimental results.
    • Here's a Figure List in English based on the provided text. Since the OCR was not perfect and some figure descriptions were incomplete, I've made educated guesses where necessary. You should verify this list against the original paper for complete accuracy.
    • Figure List
    • Figure 1: Force components acting on the vehicle.
    • Figure 2: Vehicle general model.
    • Figure 3: Internal structure block of the general vehicle model.
    • Figure 4: BLDC motor Simulink model.
    • Figure 5: Load model.
    • Figure 6: IGBT modules selected for BLDC motor driver.
    • Figure 7: Thermal resistance of the system with cooler.
    • Figure 8: Placement of IGBT modules in the heatsink.
    • Figure 9: Sample IGBT (20 mm) thermal distribution.
    • Figure 10: Sample IGBT (0 mm) thermal analysis.
    • Figure 11: Liquid cooler module top and profile view.
    • Figure 12: Liquid cooling module top view.
    • Figure 13: Liquid cooling module with IGBTs in place.
    • Figure 14: (a) Axial-flow fan; (b) Radial-flow fan; (c) Cross-flow fan.
    • Figure 15: Sandwich busbar design.
    • Figure 16: DC-Bus IGBT heatsink and capacitance.
    • Figure 17: IGBT module design on a fluid cooling system.
    • Figure 18: Original 75 kW fan-assisted natural-air cooled three-phase inverter circuit.
    • Figure 19: Original 75 kW liquid-cooled three-phase inverter circuit.
    • Figure 20: Original three-phase 75 kW liquid cooled inverter circuit with six IGBT modules.
    • Figure 21: Three-dimensional design visuals of the cooling module from the front, top and side.
    • Figure 22: SKiM459GD12E4 IGBT module, adapter circuit, and IGBT driver assembly.
    • Figure 23: (a) Original three-phase 75 kW liquid cooled inverter circuit with six IGBT modules; (b) Different angle view of Figure 23(a).
    • Figure 24: The BLDC motor's rapid control prototyping block diagram with dSpace Micro-Auto Box.
    • Figure 25: System engine-generator test platform with DS1401 dSpace Micro-Auto Box.
    • Figure 26: BLDC motor phase currents and interphase voltages.
    • Remember that this list is based on the extracted text and might not be entirely complete or perfectly accurate. Always refer to the original paper for definitive information.
Figure 18. Original 75 kW fan assisted natural-air cooled three-phase inverter circuit.
Figure 18. Original 75 kW fan assisted natural-air cooled three-phase inverter circuit.
Figure 23: (a) Original three-phase 75 kW liquid cooled inverter circuit with six IGBT modules; (b) Different angle view of Figure 23(a).
Figure 23: (a) Original three-phase 75 kW liquid cooled inverter circuit with six IGBT modules; (b) Different angle view of Figure 23(a).

6. Conclusions and Discussion:

Comparative analysis of three different power stage designs and cooling systems revealed that the liquid cooling system offered superior efficiency. This research provides valuable insights into the design of power and cooling systems for enhanced electric vehicle efficiency. The sandwich busbar design is effective in minimizing size and losses. Optimization of IGBT module spacing is crucial for reducing thermal resistance.

Limitations: The study was conducted via simulation and in a laboratory setting; performance under real-world driving conditions may differ.

7. Future Research:

Future research should focus on validating performance under real-world driving conditions, analyzing the impact of varying driving cycles on cooling system performance, and developing more efficient cooling systems and control algorithms.

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Copyright:

This summary is based on the paper "Three-Phase 75 kW Brushless Direct Current Motor for Electric Vehicles: Different Power Stage Design, Calculation of Losses, Cooling Techniques, and Comparison" by Ali Bahadir, Omer Aydogdu, and Elif Bahadir.

DOI URL: https://doi.org/10.3390/app14041365

This material is a summary and its unauthorized commercial use is prohibited.
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