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Home / Applications / High Currency Resistors

Dexmet Multipath Resistors, Load Banks and High Current Resistors:

Multipath Resistors, Load Banks and High Currency Resistors

Dexmet Multipath Resistors are used for load banks, brakes, starters and more in emergency power, power generation, test, maintenance, repair and OEM applications. They are comprised of precision cut and expanded sheet metal in various alloys as resistance elements. This precision engineered mesh offers solid, integral ends for mounting and connections. Each element is connected to its neighbor by a low resistance channel or strip of stainless metal welded in place. This design eliminates pressure and prevents changes in ohmic value from joint corrosion found in other designs. For resistors exposed to high shock, mica insulators with steel support are used. High dielectric porcelain can be used where a more economical insulator will suffice. Elements are usually comprised of either lower-cost AISI 406 steel, or Inconel (ASTM-B-168), where more flexibility is required or greater overheating occurs.

Design Factors

Heat Dissipation
The expanded metal Multipath resistor offers maximum surface area for maximum heat dissipation, either through convection or forced air cooling. Forced air cooling can more than double the power rating of convection cooled units.

Space Limitation
Multipath resistor designs acccommodate most space requirements through changes in the expanded metal strand dimensions and resistor lengths.

Accurate Reproducability
Systematic quality assurance procedures and electrically controlled production
machiner ensure accurate reproducability of Multipath resistor elements.

Weight Per Kilowatt
Where weight is critical, as in mobile vehicles, the need for massive grids and heavy supports are eliminated with expanded metal resisitors.

Cost
For high current-low resistance applications, costs can be reduced as much as 40 to 60 % below competitive designs due to decreased material and a greater design flexibility.

Technical References

Two basic designs are used; The flat element (Figure 1A) and the girder element (Figure 1B). The choice of element design is dictated by current, space, resistance, allowable temperature rise and cooling requirements. Experience has shown that a six mesh unit (6-3/4") is the maximum flat element design with mechanical integrity. Current application requiring wider strips are formed into girder elements. An example of the range of rating variations is shown in Figure 2. Current ratings in this chart assume a convection cooled atmosphere with an ambient temperature rise of 350° C.

The expanded length of this strip dictates its resistance value in relation to width, described as "number of meshes". "Number of meshes wide" is a controlling factor for current rating within a specific metal thickness and strand configuration. Please also note that the "three-mesh-wide" strip can carry 35 amperes, 62 amperes, or 91 amperes by varying material thickness and strand width. Of course, as the current rating increases, the resistance rating would decrease. Current resistance combinations anywhere in between those detailed in this chart are also available.

Slope Resistors
Current Sensors
Grounding Resistors
SCR Control
Dynamic Braking
Welding Controls

Dexmet Multipath Load Banks are designed for acceptance testing equipment such as switchgears, motors or generators and for Control Load Banks to maintain the integrity of emergency power systems, for dynamic braking or grounding resistor loads. Quality Control and R&D laboratories employ Load Banks for a range of tests in industries from power generation and transportation to aerospace, naval and military applications. Emergency and standby power systems must also be operated periodically to ensure that they work. Most systems employ diesel generators, whose manufacturers and consultants recommend testing under load for proper flow of lubricating oil, sealing of gaskets and rings and circulation of coolant.
The convenient, reproducable method to control load and timing is to employ a dummy load bank. Whether fan or convection cooled, in the engine room or on the roof, flexible Dexmet designs fit requirements for a range of applications.

Charts

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