Aqueous-Electrolyte Resistors

• Introduction
• Specifications
• Representative Resistors
• References

High-voltage, low-inductance resistors are commonly employed as fast voltage-divider probes, charging/trigger resistors in capacitor banks, dummy loads for pulsed power systems, absorbers of reflected pulses, and energy dumps. An aqueous electrolyte, such as potassium dichromate or copper sulfate, is a convenient resistive medium with high dielectric strength and stability under high electric fields. Properly designed aqueous-electrolyte resistors can repeatedly dissipate large energies without catastrophic failure. Aqueous electrolytes are characterized by a negative temperature coefficient of resistivity; for typical operating conditions (electrolyte concentration and temperature), this coefficient is in the range (1/R)(dR/dT) = -(0.01 to 0.03) ⁰C^-1.

Aqueous-electrolyte resistors are technically superior to wirewound, film, and composition resistors and less expensive than ceramic resistors. Wirewound resistors have significant self-inductance and only modest energy dissipation capability. Film and composition resistors are prone to arc over and catastrophic failure. All competitive solid-state products are of fixed resistance, whereas the resistance of aqueous electrolytes can be readily changed by adjusting the electrolyte concentration.

Our model R-100 resistors are small-volume devices that are available as demountable kits in three standard lengths. Other lengths are available on a custom-order basis. An internal hydraulic valve and reservoir relieve any over-pressure during pulsed operation while permitting horizontal or vertical mounting. Brass electrodes and a polycarbonate casing prevent contamination of the electrolyte solution and resistance change with age. Viton® O-rings ensure leak-free service and allow immersion in compatible dielectric oil. Multiple resistors can be operated in parallel for even greater energy dissipation and lower inductance. These resistors are ideal as dummy loads for capacitive discharges and pulse-forming lines or in any high-voltage application where self-inductance is a problem.

Models with stainless-steel electrodes [R-100-SS-(gap)-K] are available for special applications. The resistance of an individual unit can be decreased to <10 Ohms (please inquire). Depending upon ambient conditions (altitude and relative humidity), operation in excess of about 50 kV will require immersion in a dielectric medium such as SF₆ or mineral-base transformer oil.

Our model R-201 resistor was developed for use as a stable dummy load at high average power. The combination of large electrolyte volume (10 liters) and active internal cooling minimizes solution heating and ensures relatively constant resistance during operation. This resistor can dissipate an average power of 100 kW for a 10-s pulse burst, and correspondingly lower average powers for longer durations. The single-pulse energy dissipation is in excess of 200 kJ. The typical resistance range is ~0.1 to 50 Ohms. Model R-201 resistors are available only on a semi-custom basis with the design optimized for the particular customer's needs.

Specifications are subject to change without notice. Pricing for standard resistors may be obtained from the links given on our Sales page. Inquiries for additional product information are welcome!