The DCRF resistors from Vishay Intertechnology Inc. are available in footprints ranging from 38 mm × 178 mm to 38 mm to 410 mm. They have resistance values ranging from 0.56Ω to 27Ω with tolerance values of ±5% and ±10% and can be operated with a maximum working voltage up to 3,600V.
DCRF series resistors have a temperature coefficient of 100ppm/°C, a water inlet temperature of 65°C, 40% mono ethylene glycol, 8.33l/min (litre per minute) flow rate, and they can be operated under temperatures ranging from −55°C to 120°C. They also have a water conductivity that is less than 2μs/cm.
As per the datasheet, the resistor’s core and the hydraulic plugs are made of stainless steel, while the windings are made of nickel-chrome (NiCr). Being a series of power wire-wound resistors, they can be subjected to pressures ranging from 1 to 6 bars when in use.
For systems that require high power, the product has high power ratings (up to 9,000W) with little or no external radiation. The DCRF series offers direct cooling without the use of heat sinks and features a multi-resistive element option.
DCRF wire-wound resistors are eco-friendly products and RoHS-compliant. They are lead-free (<1000 ppm) and halogen-free (<900 ppm of Bromine—it contains less than 1,500 ppm of Bromine and Chlorine combined). They also comply with guidelines from the IEC 62474, Global Automotive Declarable Substance List (GADSL), and the Registration, Evaluation, Authorisation and Restriction of Chemicals (aka REACH).
A close-up of an industrial electrical device for which direct water-cooled wire-wound resistors are suitable for use. Image Credit: Vishay Intertechnology, Inc.
Comparison with Similar Wirewound Resistors
Vishay Intertechnology also provides a series of indirect water-cooled wire-wound resistor series (aka the WCR series). These are without the high power-rating of the direct water-cooled resistors. Resistance values for WCR resistors range from 4.7Ω to 56kΩ with a tolerance of ±5%.
The indirect WCR series maintains the same temperature coefficient of 100ppm/°C as the direct water-cooled series resistors and (as per the above) it operates within a temperature range of −55°C to 120°C.
Non-water-cooled wire-wound resistors like the RWM series operates at a lower voltage range than water-cooled resistors (from 120V to 800V). Their power rating is about 30W, which is not suitable for high power dissipation like the DCRF series. Their ohmic values range from 0.1Ω to 100kΩ—with tolerances between ±1%, ±2% and ±5%.
The DCRF series is non-inductive, and therefore suits filter, snubber, and discharge resistors for industrial applications. They have a good power-to-volume ratio, which makes them suitable for use in large drives, high voltage direct current (aka HVDC) systems and battery management systems.