280 Series RoHS Compliant Vitreous Enamel Fixed and Adjustable Power Resistors

Category: Electronics, Ohmite Manufacturing Co, Resistors

Overview

The 280 Series resistors are RoHS compliant, vitreous enamel-coated power resistors, suitable for applications involving high currents with very low resistance values, starting as low as 0.1Ω for the 300 Watt unit. These resistors are designed to endure frequent start-stop cycles, commonly seen in motor starting and dynamic braking applications. Available for special order, these resistors can handle capacities up to 1500 watts.

Features

The resistors come in a tubular ceramic form with corrugated resistive wire, aiding in enhanced cooling. This wire is securely fused to the ceramic core with a lead-free vitreous enamel coating for increased durability. For physical attributes, the 35 Watt model dimensions are specified, alongside the 300 Watt model available in both fixed and adjustable terminal types.

Specifications

The series offers options ranging from 35 watts to very large models exceeding 750 watts which come with a silicone coating. The power rating is based on a 25°C free air rating and a linear derating to 0% as temperatures reach +400°C. Overload capacity is set at 10 times the rated wattage for 5 seconds. Electrical resistance values for the 300-watt model max out at 630Ω, with standard tolerances of ±10%.

Materials and Construction

With a focus on performance in extreme conditions, materials include cores either of Centohm or Silicone construction, and the series features coated leads of lead-free vitreous enamel for the lower wattage models and silicone ceramic for the higher wattage models. These materials have an associated temperature coefficient of ±400ppm/°C. Dielectric withstanding voltage is recorded at 1000VAC from terminal to mounting bracket.

Ordering Information

Standard part numbers are provided for the 280 Series, with specifications covering minimum and maximum ohms, the diameters, and lengths of the cores. Additionally, there’s guidance on how to specify custom parts via Ohmite’s website, as well as how to order resistors with a high wattage that require a silicone coating.

Mounting and Hardware

For the 300 Watt resistors, the datasheet outlines available hardware for mounting, including bolts, brackets, and washers. It also discusses different levels of rated wattage and features an extensive list of part numbers that vary by the core size, wattage, and resistance.

Contact Information

For further inquiries or to place orders, Ohmite Manufacturing’s contact details, including phone numbers and email, are provided, along with the corporate address and website.