Sunday, February 25, 2024

High-Voltage Resistors For EV Powertrains

By Nidhi Agarwal

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The resistor series boosts electric vehicle powertrains, meeting diverse needs in high-voltage automotive applications.

RVCA series thick film, high-voltage chip resistor. Image used courtesy of Stackpole Electronics.
RVCA series thick film, high-voltage chip resistor. Image used courtesy of Stackpole Electronics.

The RVCA, launched by Stackpole Electronics Inc. based in Raleigh, N.C., is a thick film chip resistor series tailored to the demanding application needs of 400 V and 800 V electric vehicle (EV) powertrain buses.

The RVCA series is AEC-Q200 qualified and meets standard test requirements for load life, biased humidity, short time overload, and temperature cycling, which makes it suitable for high-voltage automotive applications.

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This surface-mountable resistor series includes six models with voltage ratings from 100 V to 3000 V and comes in standard resistor package sizes from 0402 to 2512. Parts are available with resistance values from 30 kΩ to 100 MΩ and specified to 1% or 5% tolerances.

The series is used in monitoring, driving, and controlling circuits within and across the isolation boundary of an EV high-voltage powertrain bus. Applications include voltage, short circuit, DESAT protection, gate-drive, temperature monitoring, self-test, and soft-start circuits.

Pre-charge circuits are an application for high-voltage resistors in electric vehicles (EVs). EV motor inverters and similar loads have large input filter capacitors. During start-up, charging these capacitors can cause high in-rush currents that might damage electrical connectors and components. The pre-charge circuit manages this by including a high-voltage resistor with the input capacitance, extending the circuit’s time constant and limiting the capacitor charging current. Once the load capacitance is charged, the pre-charge resistor is bypassed for normal operation of the vehicle’s electric powertrain. The pre-charge circuit also reduces regular operational stress, enhancing the lifespan and reliability of the system.

The RVCA2512, the largest in the RVCA series, has a power rating of 1 W at 70°C, a maximum operating voltage of 3000 V, and an overload voltage of 4000 V. Power dissipation capabilities decrease linearly from 70°C to 155°C. The 2512 package measures 6.35 mm x 3.1 mm with a height of 0.55 mm, and all models in the chip resistor series are suitable for surface mounting in PCB manufacturing.

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