Direct water-cooled wirewound resistors save space and boost reliability

A new series of direct water-cooled wirewound resistors that offers ultra high power dissipation to 9000W with almost no external radiation has been launched by Vishay Intertechnology.

Available in six compact sizes ranging from 38 mm x 178 mm to 38 mm x 410 mm, Vishay MCB DCRF series devices are designed to save space and increase reliability over standard wirewound resistors.

The resistors released can handle 10 times the power of natural-cooled devices in the same size, and two times the power of indirect water-cooled devices. By replacing multiple components with one resistor, the DCRF series helps designers to simplify layouts and reduce the size of their end products. The devices’ modular structure enables a multi-resistive element option.

Optimised as load, filter, snubber, and discharge resistors in large drives, HVDC and battery-management systems for industrial applications, the resistive elements of DCRF series devices are in direct contact with water and insulated by ceramic tubes, eliminating the need for a heatsink.

With almost no or limited external radiation, the resistors increase reliability by limiting the surface temperature, while a safe failure mode prevents leakage in the event of a water-flow shutdown. The devices can handle an overload of two times nominal power for 60 s without damage.

The DCRF series offers low inductance (< 500 nH for model DCRF 38 x 178 with resistance of 4.7-Ohm) and provides a resistance range from 0.56-Ohm to 27-Ohm, with tolerances down to ± 5%.

The devices feature power ratings from 1500W to 9000W with a water inlet temperature of 65 degrees C and 8.33 l/min flow rate (deionised water with conductivity < 2 micro-S/cm).

RoHS-compliant and lead (Pb)-free, the resistors offer a typical temperature coefficient of 100 ppm/ degrees C and operate over a temperature range of -55 degrees C to +120 degrees C.

Samples and production quantities of the DCRF series are available now for the 38 mm x 178 mm size with resistance of 1.6-Ohm and 3.2-Ohm.

Lead times are 15 weeks for larger orders.

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