Vitreous Enamelled Wirewound Resistors – WZO Series – TT Electronics

Category: Electronics, Resistors, TT Electronics PLC

Overview

TT Electronics presents its WZO Series of Vitreous Enamelled Wirewound Resistors, suitable for harsh environments due to their impervious lead-free vitreous enamel coating. They are CECC approved and meet or exceed the requirements of BS CECC 40-201-002. These resistors are characterized by exceptional overload characteristics making them ideal for protection circuits, along with high stability, reliability, and power dissipation relative to their size.

Compliance

Aligning with environmental directives, all Pb-free parts comply with the EU Directive 2011/65/EU, amended by (EU) 2015/863 (RoHS3).

Electrical Data

The series includes several types classified by size and power ratings, from the W21 with a power rating at 25°C of 3.0 watts, up to the W24 with 14.0 watts. Resistance ranges are provided with 1%, 2%, and 5% tolerances across values from 0.1Ω up to 100KΩ. They exhibit a temperature coefficient of resistance (TCR) typically less than ±15 ppm/°C, with a maximum of ±200 ppm/°C.

Physical Characteristics

The resistors have a high purity ceramic substrate and interference fit end caps, with welded termination wires. Their construction ensures durability with a protective coating. Termination materials are comprised of copper-clad steel wire, nickel-plated, and solder-coated, meeting the strength and solderability requirements of international standards such as IEC 68.2.21 and IEC 115-1 Clause 4.17.3.2.

Operating Conditions

Operational features include a range of limiting element voltages from 100 volts to 750 volts, with standard E24 values available, and others to special order. The thermal impedance is rated at ≤20°C/Watt, and the ambient temperature range within which the resistor operates effectively is from -55°C to +200°C. The physical dimensions of the resistors vary with type, as described in the datasheet, ensuring a fit for various applications.

Marking and Packaging

Each resistor is marked with the type reference, resistance value, and tolerance, according to IEC 62. The minimum lead length provided is 30 mm, and certain types are available in taped packaging.