Vitreous Enamelled Wirewound Resistors – WZO Series

Category: Electronics, Resistors, TT Electronics PLC

Overview

The datasheet details the WZO Series of Vitreous Enamelled Wirewound Resistors, a product of TT Electronics designed for use in harsh environments. This series is CECC approved and particularly suitable for protection circuits due to its overload characteristics. With its lead-free vitreous enamel coating, the WZO Series offers high stability, reliability, and power dissipation relative to size.

Electrical Data

The resistors come in various models (W21, W215, W22, W23, W24), with power ratings ranging from 3.0 to 14.0 watts at 25°C. They cover a resistance range from 0.1 ohms up to 100K ohms and are available in three tolerance bands: ±1%, ±2%, and ±5%. The Temperature Coefficient of Resistance (TCR) for these resistors typically falls below ±15ppm/°C but can go up to a maximum of ±200ppm/°C, indicating reliable performance over a wide temperature range (-55°C to 200°C).

Compliance and Ratings

In compliance with BS CECC 40-201-002 requirements, the WZO Series matches or exceeds these standards. Power ratings drop slightly when operated at higher ambient temperatures, such as 70°C. The datasheet also provides CECC specification requirements by style (HB, KB, LB, MB) for power ratings and resistance ranges. The WZO Series components meet all the requisites for the commercial and approved ranges.

Physical and Construction Data

The physical attributes include a high-purity ceramic substrate with end caps and welded termination wires. The vitreous enamelled protective coating affords the resistors their stability and durability. The termination wires, made of copper-clad steel, are nickel-plated and solder-coated, conforming to IEC 68.2.21 for strength and IEC 115-1 – Clause 4.17.3.2 for solderability.

Design Features

These resistors possess a limiting element voltage ranging from 100 to 750 volts, thermal impedance rated at 58°C/watt, and can operate within an ambient temperature window of -55 to +200°C. They come in various dimensions and weights specified by type and maintain minimum lead lengths of 30 mm. For identification, resistors are marked with type reference, resistance value, and tolerance in accordance with IEC 62.

Additional Information

The standard E24 values are preferred, but the company accommodates special orders for other values as well. TT Electronics notes that specifications are subject to change without prior notice. It is recommended to consult the TT Electronics website or contact them directly for the latest product information.