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Use Cases
Use Cases

Real-time Efficiency Measurement on Inverter and Electric Motor

The optimal design of inverters is necessary for increasing the range per charge and performance of electric vehicles. The inverter is the link between the battery and the electric motor and plays an important part in the electric powertrain. This application example shows how power and efficiency calculations are performed on the inverter and how the measurement setup can easily be expanded for further measurements.

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When converting DC from the battery into three-phase AC, which is used to regulate the three-phase electric motor, part of the energy is lost due to PWM switching performance and waste heat in the inverter. These losses must be kept as low as possible. The efficiency of the inverter is a suitable parameter to evaluate changes in design and software. Ideally, the efficiency of the inverter can be directly correlated with the efficiency of the associated electric motor.

Measurement task

Measurement of electrical input power and electrical output power for the calculation of the inverter efficiency.

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To determine the inverter efficiency, the electrical input and output power must be measured synchronously and in a high-voltage safe manner. The measurement must be carried out with high data rates and phase accuracy in order to have suitable data for a precise calculation. At the same time, temperatures in the inverter must be measured in order to analyse the effects of thermal changes on the performance. If the efficiency of the electric motor is also to be calculated in parallel, the mechanical output power must also be measured.

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The CSM Measurement Solution

The solution for this measurement task is found in the perfectly harmonized Vector CSM E-Mobility Measurement System, which combines precise measurement modules and powerful software.

  • A HV Breakout Module (HV BM) 1.2 measures current and voltage between the battery simulator and the inverter at a data rate of 1 MHz. For this purpose, the HV BM is simply inserted in the power cables by routing the HV cables through cable glands in the housing.
  • Current and voltag between the inverter and the electric motor are measured with a HV Breakout Module 3.3. This module allows the synchonous measurement of current and voltage in all three phases.
  • Alternatively, both Breakout Modules can also be connected to the HV power cables using a PowerLok connector system (HV BM 1.2C and HV MB 3.3C). This simplifies the exchange of DUTs if different setups are to be analyzed.
  • The temperatures in inverter and electric motor are measured with HV-safe temperature measurement modules HV PTMM and HV THMM. Due to the special CSM safety concept, standard PT sensors and thermocouples can be used.
  • With speed torque sensors and a CNT evo the mechanical output power of the electric motor is optionally measured.
  • All EtherCAT® measurement modules (HV BM) and CAN-based modules (HV PTMM) are connected to the HV BM 3.3. The EtherCAT® signals are synchronized and the CAN signals are bundled. The data is converted to XCP-on-Ethernet with up to 2 GBit/s.
  • Internal measurement variables of the power electronics are synchronously acquired via a Vector network interface VX1000. These measurement values and the external measurement data are synchronized via the "Precision Time Protocol (PTP)".
  • Efficiencies are calculated in real-time in the eMobilityAnalyzer function library for Vector vMeasure or CANape. The internal measured variables can be directly correlated here with the calculated efficiency values.
Efficiency Measurement in E-Mobility Measurement System
Presentation of the efficiency measurement in the systematics of the Vector CSM E-Mobility Measurement System
eMobilityAnalyzer surface
The eMobilityAnalyzer for Vector vMeasure and CANape calculates all necessary values in real-time.
eMobilityAnalyzer E-Motor Power Analysis
The E-Motor Power Analysis function is used to calculate all relevant power parameters and efficiency.
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With the Vector CSM E-Mobility Measurement System, the calculation of the overall efficiency can be done in real time. Due to the robust and compact measurement modules, the measurement can be performed both on the test bench and in road tests. The test setup is shortened to a few components, which reduces the time required for the test setup and increases the quality of the measurement.

Furthermore, the Vector CSM E-Mobility Measurement System allows easy integration of additional measurement modules for further measurement variables, e.g. temperatures.

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