High-voltage resistant temperature sensors for connectors in electromobility

November 16, 2021 // By Christoph Hammerschmidt
High-voltage resistant temperature sensors for connectors in electromobility
In electromobility, constant monitoring of the temperature of all system units is required. Due to the high currents, losses occur especially at contacts with corresponding heat generation. TDK has now developed a special high-voltage-resistant temperature sensor for connectors.

High-voltage batteries for electric vehicles (xEV) have nominal voltages of up to 1000 V, which requires corresponding high-voltage resistance of all system components. In order to achieve high drive powers of sometimes significantly more than 100 kW via inverter and motor, currents occur that are in the triple-digit range. These high currents, in conjunction with line and contact resistances, lead to not inconsiderable power losses and thus to heat loss, since the currents are included in the calculation quadratically: PV = I2 x R. Thus it becomes clear that even small resistances in the milliohm range lead to relatively large losses and thus to heating that can assume critical values.

For this reason, critical contact points in xEV - for example connectors between battery and motor inverter - must be thermally monitored. If overheating is imminent, the current can then be throttled in time. NTC-based temperature sensors that initiate a derating of the current are suitable for monitoring the temperature at critical points. Figure 1 shows the control principle.

Electromobility places completely new demands on the development and design of NTC temperature sensors - especially for integration in high-voltage systems. These include:

  • High voltage resistance
  • Short response time
  • High temperature resistance
  • High accuracy
  • Possibility of integration directly into connectors

The challenge was to find a material that had high electrical insulation properties, but also very good thermal conductivity, in order to develop a design in which an NTC element could be integrated. In addition, a high temperature resistance had to be offered. A sleeve made of a special ceramic in which the sensor element is integrated proved to be suitable. Figure 2 shows the temperature sensor developed in this way.

The design of the new temperature sensor for integration into connectors. By using a ceramic sleeve in which the NTC element is integrated, the required high voltage resistance and short response time could be realised.

Several tests have proven that

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