Mercury Displacement Relays are all designed and built to meet the most exacting demands of industry. They have won their high place in the electrical field by doing the tough and tricky jobs that ordinary equipment could at best do in an uncertain manner.
They have proved their ability to stand up under the most adverse conditions of temperature, dust and moisture, in all types of applications. All the care required for the manufacture of high-grade instruments is used in the manufacture of the switches. All switch parts are specially cleaned, and contamination is avoided by use of tweezers, gloves, etc., when making assemblies.
Contactors are hermetically sealed with high quality glass to metal seals. The stainless steel tube is totally encapsulated in high grade UL approved epoxy to prevent moisture damage and voltage breakdown through the protective coating.
The coils are wound on compact nylon bobbins and molded onto the metal tube to provide minimum power loss. This allows for low coil power required to actuate the contactor. This also enables the units to handle high loads with minimum derating due to higher ambient temperatures.
Inert gases internally prevent excessive arcing between the mercury and the electrodes which enables the unit to function for millions of cycles with very low contact resistance, and minimum deterioration of the internal parts.
Our mercury relays are available in all standard coil voltages, in single, two and three pole arrangements. Other coil voltages available upon request.
In multiple pole units each tube is actuated by its own coil. This eliminates pull-in variation between contact tubes, assuring consistent switching.
100 amp version may be used as high voltage contactor. Ideal for UV curing and various high voltage applications. Ratings are 10 amps @ 3500VAC, 15 amps @ 2500VAC, AC inductive power factor .7 or greater.
Mercury relays are also referred to as mercury contactors, mercury relay switches, mercury contactor relays and mercury displacement relays.
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Manufactured by MDI Mercury Relays
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30 to 100 amp
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One, two or three pole
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AC or DC voltages
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-18 on the end simply means steel strap around the poles vs. a nylon one
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Designed to save space
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Simplify mounting methods
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Longevity: millions of cycles
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Low coil power requirements
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Normally closed available, please contact us.
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Note: 100 amp contactors may be derated for use as high voltage contactors
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10 amps @ 3500VAC
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15 amps @ 2500VAC
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AC inductive power factor .7 or greater
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Available in single pole, normally open and normally closed units
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Ideal for UV curing and various high voltage applications!
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High voltage available for UV applications including drying wood, paint, powder paints, particle board and more
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MDI has an exemption to sell high voltage contactors in the state of IL for OEM applications



When looking for Mercury relays, consider MDI. Marshall Wolf Automation is your industrial supply distributor for MDI mercury relays, call us at 847-658-8130, or email us at sales@wolfautomation.com. Contact us we can help!