ULW Series Wirewound Resistors

TT Electronics/Welwyn ULW series is designed to withstand inrush and surge conditions

Welwyn's ULW Series Wirewound ResistorsTT Electronics/Welwyn ULW series wirewound resistors overcome the problems associated with conventional flameproof resistors caused by the ceramic rod at the resistor's core acting as a heat sink for the wire element. This can delay fusing, resulting in high enough temperatures to fragment the coating and ionize the air near to where fusing occurs. If ionization occurs close to the cap edge and at a voltage peak in the mains cycle, it can initiate a momentary flashover outside the component body, releasing far more energy than is required to fuse the wire element. Although the opening of the circuit is safe for most applications, it is far from silent.

The devices are designed to withstand inrush and surge conditions. For example the ULW4-10RJ has an energy limit of 4.3J and a 1.2/50μs peak voltage limit of 1.1 kV. Fusing performance is characterized by typical fusing times of 8 seconds at 45 W initial power (ULW2) and 10 seconds at 90 W initial power for ULW3 and ULW4 resistors, although rapid fusing in a fraction of a second is achieved under mains short circuit conditions.

ULW Series Wirewound Resistors

ImageManufacturer Part NumberDescriptionAvailable Quantity
ULW2-33RJA25 datasheet linkRES 33 OHM 2W 5% AXIALULW2-33RJA25RES 33 OHM 2W 5% AXIAL740 - Immediate
ULW2-33RJA25 product page link
ULW2-100RJA25 datasheet linkRES 100 OHM 2W 5% AXIALULW2-100RJA25RES 100 OHM 2W 5% AXIAL474 - Immediate
ULW2-100RJA25 product page link
ULW2-22RJA25 datasheet linkRES 22 OHM 2W 5% AXIALULW2-22RJA25RES 22 OHM 2W 5% AXIAL99 - Immediate
ULW2-22RJA25 product page link
ULW3-10RJA1 datasheet linkRES 10 OHM 3W 5% AXIALULW3-10RJA1RES 10 OHM 3W 5% AXIAL947 - Immediate
ULW3-10RJA1 product page link
ULW3-27RJA1 datasheet linkRES 27 OHM 3W 5% AXIALULW3-27RJA1RES 27 OHM 3W 5% AXIAL918 - Immediate
ULW3-27RJA1 product page link
ULW3-47RJA1 datasheet linkRES 47 OHM 3W 5% AXIALULW3-47RJA1RES 47 OHM 3W 5% AXIAL478 - Immediate
ULW3-47RJA1 product page link
ULW2-47RJA25 datasheet linkRES 47 OHM 2W 5% AXIALULW2-47RJA25RES 47 OHM 2W 5% AXIAL620 - Immediate
ULW2-47RJA25 product page link
ULW3-22RJA1 datasheet linkRES 22 OHM 3W 5% AXIALULW3-22RJA1RES 22 OHM 3W 5% AXIAL0ULW3-22RJA1 product page link
Published: 2011-02-15