All the Moving Parts in Transportation

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The transportation industry is one that in whatever form it takes—cars, trains, heavy construction equipment for construction or agriculture, tractors, snowmobiles, military ground vehicles, elevators, escalators, and more—is constantly on the move. So, there’s an irony in that one of the important components in circuitry design for the sector is one that doesn’t stir on its own: resistors.

Resistance is part of any electrical circuit and a critical component in many types that are widely used in transportation. Dynamic braking, power supplies, custom controls, lighting, and any other electrical system will need various types of resistors that can handle the demanding needs, like high stability, compact sizes, tight tolerance, low temperature coefficients of resistance for thermal stability, high power ratings, ability to withstand high transients, a variety of mounting choices, EMI interference considerations, and different construction types and the performance and characteristic trade-offs they offer.

Transportation applications often involve harsh conditions, whether high temperatures, presence of corrosive materials, moisture, dirt and dust, vibrations, impacts, physical contact, static charges, chemicals like pesticides and fertilizers, and more. Ohmite has entire lines of resistors for transportation that include metal plating to prevent oxidation of metal parts. There are also the considerations of how parts can affect the environment in which applications are deployed, which is why lead-free, and RoHS (Restriction of Hazardous Substances Directive) compliance are available.

Specifically for transportation use, Ohmite has multiple different product types, including resistors and rheostats, that can be a match for design needs. The 270 series is a lead-free vitreous enamel-coated power resister with power ratings from 12W to 1000W. Higher power versions are in silicone ceramic, though low-cost flame-proof Centohm coating. Lug terminals are suitable for solder or bolt-on connection. The 280 line is for high-current applications with low resistance values and is designed to withstand frequent start-stop cycles characteristic of motor starting, dynamic braking, and other similar applications.

The Ohmite ARCOL brand HS Series is a high-performance molded-construction metal-housed resistor. Aluminum housed, they are compliant with MIL 18546, IEC 115, and RoHS, and are designed for direct heatsink mounting with thermal compound to achieve maximum performance. They offer high power to volume ratios, are wound to maximize high pulse capability, and are suited to withstanding vibration, shock, and harsh environmental conditions.

MMV thick-film resistors automotive-grade chips are AEC-Q200 compliant and available in popular sizes ranging from 0201 through 2512 and in three versions: standard, high-precision, and high-power. They offer great stability and, with the high-precision version, tolerance of 0.5%.

PFE and PFR series are available in both edgewound (for low resistance and high power) and round wound formats. These rugged resistors handle between 700W and 1000W of power. Construction includes a heavy resistance alloy mounted on ceramic insulators and supported by a metal mounting bracket. Metal parts, except for the resistance element, are heavily plated to prevent oxidation at high operating temperatures and to prevent corrosion.

The heat sinkable planar TAP600 dissipates 600 watts of power for a variety of power conditioning, power transmission, and power control applications. The resistors offer low inductance and capacitance. They are encapsulated with a special resin filled epoxy casing with a large creepage distance to mass, large air distance between terminals, and a high insulation resistance (CTI 600). Available for either liquid- or air-cooled heat sink systems, applications include variable speed drives, power supplies, robotics, motor control, and other control devices. The TAP800 dissipates 800 watts of power while the TAP1000 and TAP2K0 respectively handle 1000 and 2000 watts.

Resistor load banks like the HCLB series are commonly used for dynamic braking on transit applications or where high current handling and wattage are required. Made for rugged environments, they feature corrosion-resistant stainless-steel insulator supports, solid nickel terminals, and special electro-less nickel-plated solid copper terminal supports. The resistance element is made of a stainless-steel resistance alloy. Terminals are welded or silver brazed to the oval, spiral edgewound resistance element. Toothed ceramic insulators isolate the resistance element from the center support. The SGM series uses stamped grid technology in a modular format. The design incorporates several resistive plates, fitted on steel rods, that are separated by ceramic rings. This design offers size and weight advantages over regular wirewound grid assemblies.

Ohmite offers many resources and deep expertise in identifying the type of resistor that is best suited for your transportation application. Contact Ohmite today.