Detailed Information

1kV to 300kV
1mA to 800 Amps

115V, 60Hz actuators are standard for pull-in currents less than 10A. Higher actuator voltages are recommended for pull-in currents over 10A to minimize momentary voltage drop. It is recommended that source impedance allow no more than 6% drop at the coil terminals during pull-in. Most models can be supplied with actuators for 24V, 48V, 70V, 100V, 115V, 200V, 208V, 230V or 480V, and 60Hz or 50Hz power. 400Hz or 24V, 48V, 100V, 115V or 125V DC actuators are available at additional cost. Latching type actuators are also available requiring only momentary current. Special actuators and relay drivers are available for high speed operation of 0.5 to 10 milliseconds, or delayed operation upon loss of power. Air or hydraulic pressure actuated relays are available for applications requiring complete electrical isolation of the actuator, very high contact pressure for high current or very long strokes for higher withstand voltage ratings. Electric motor actuators are also available for special applications. A small PC board is available to be inserted at the coil input which will eliminate AC HUM and prevent coil burn-out on failure to pull in.

Most of the Ross Engineering Corporation high voltage relays with ratings through 60kV can be adjusted to be mounted in any altitude unless otherwise indicated. Where maximum reliability, minimum noise (HUM), minimum contact resistance, or minimum pull-in voltage is required, consult the Applications Engineering Department for mounting recommendations. Please specify mounting position; base down is standard and will be optimum unless otherwise noted. Most of the Ross Engineering Corporation solenoid operated high voltage relays with ratings of 70kV or higher are designed to return to their normal position by gravity when the actuator is de-energized. These relays must be mounted in the recommended altitude. Ross Engineering Corporation switches operated by air or oil pressure, or by electric motors, generally may be mounted in any altitude.

High contact closing force enables high momentary current closing capabilities ranging from 10A to 50,000A. Special tungsten contacts are available to increase momentary discharge current ratings by many times, but with reduced continuous current ratings. Continuous current ratings drop and contact resistance may increase with standard copper alloy contacts when arcing occurs or in a dusty environment, therefore special silver contacts are available to maintain continuous current ratings when closing or opening under load.

Continuous current ratings are as of new and clean condition for a maximum of 40°C ambient at sea level. Relays are suitable up to 70°C ambient with forced ventilation. Current ratings as specified are continuous for 60Hz RMS and DC, but should be derated 3% per 1,000ft above sea level. Continuous current ratings of standard copper alloy contacts are reduced after arcing. Special silver contacts must be used where continuous current is required after arcing if current ratings are to be maintained. Type of application should be considered when determining current rating required. In most cases, continuous currents for long time duty should not be more than 3/4 the current rating of the new relay. In open industrial or dusty atmosphere it may be necessary to derate by 50%, further if arcing occurs unless silver insets are used. Some units can be used in applications above 60Hz at reduced current and voltage ratings. All RF applications should be submitted to our Applications Engineering Department for review.

These air insulated relays are not rated for current interrupting. Most are capable of interrupting 10 milliamps or more depending on type of wave, load, and recovery voltage. Much higher currents can be interrupted in insulating gas or oil and with certain other applications and models. High voltage air insulated relays can close on high short time capacitor discharge currents and are rated for safety grounding or high current capacitor dumping. They have long life and little or no maintenance in these applications. Tungsten contacts are available for longer life capacitor discharge use. Fail-safe grounding or shorting relays of this type with fully visible contacts are ideally suited for use in all types of power supplies. Relays, contactors and switches for higher interrupting capabilities are covered in other brochures.

Ratings are for air at 760mmHg, 20°C. Derate 3% per 1,000ft above sea level. All peak test voltages are 1 minute 60Hz peak hold voltages, unless otherwise noted. The first figure in the model number is the peak test rating between open contacts. The number following the contact configuration designation is the rated peak test voltage to ground. On most non-spherical contacts, transient pulse withstand may be considerably higher than the 60Hz test level. Actual flashover values, for spherical types, are approximately 10% greater than rated peak test hold values for DC, 60Hz, and most transients.

The peak test rating of high voltage relays should be 1.2 to 5 times the normal high voltage circuit operating voltage, depending upon the application. For lower power systems, where transients are unlikely or intermittent flashover is of no consequence, a safety factor of 1.2 to 1.5 may be suitable. For medium power systems, or where moderate transients are likely, a safety factor of 1.5 to 3 is desirable and 2 to 3 recommended. For higher power systems, or where transient over-voltages are expected, a safety factor of 2.5 to 5 should be considered and the factor should be based on the maximum probable transient. The peak test voltage to ground rating should be selected in the same way as is the contact to contact value. If a value other than the published rating is required, it can normally be supplied as an extra cost option. On most grounding relays, even though one contact is grounded, the insulation to ground should be 10kV to 40kV to prevent HV ground current from flowing in solenoid circuits during capacitor discharge, or transients.

Standard insulation used on Ross Engineering Corporation high voltage relays and switches is fire retardant FR-4, G-10 or G-11 Epoxy glass laminate. G-7 silicone glass insulation is recommended as an extra cost option for RF applications, particularly above 300kHz. It also may be necessary to increase insulation length for RF Applications.

The voltage withstand value is at least doubled or tripled and the interrupt capability is much greater when the relay is immersed in insulating oil, fluid, or gas. No modification is necessary for operation in an insulating gas atmosphere; however, oil or fluid immersion requires modifications and is an extra cost option. For maximum performance in an insulating medium, where high voltage is impressed directly across solid insulation, it may be necessary to increase insulation length to prevent puncture at levels above the test rating in air.

Auxiliary contacts are available on request on all relays. Most smaller relays are optionally available with at least two 10A, 250V AC or 3A, 24V DC auxiliaries. Larger units are available with at least two 15A, 480V AC auxiliaries, and some have provision for as many as eight. 10A, 115V DC auxiliaries are available interchangeably with the 15A, 480V AC units. Oil-immersed relays require special auxiliaries. Optional auxiliary contacts can indicate fully open or fully closed HV relay.

OSHA and other safety regulations indicate safety grounding of all HV power supplies and systems for personnel protection. Ross Engineering helps meet these requirements with its line of high voltage grounding and discharge relays and accessories.

Thousands of trouble free high voltage applications in the past 42 plus years have established Ross Engineering Corporation's reputation for dependable, quality engineered products. Fire retardant high strength epoxy glass laminate insulation with a moisture resistant coating is standard on most units. Heavy duty contacts, which are specially designed to minimize corona, are made of highly conductive but weld resistant alloys. Ross Relays are noted for their ability to withstand high shock and vibration as well as other severe environmental conditions.

Simplicity of mechanical design and conservative stress levels result in long trouble-free life. Contacts on most relays may be rotated to renew the contact area, resulting in even longer service life.

Ross Engineering Corporation manufactures some of the most compact air insulated high voltage relays available. The best qualities of mechanical and electrical design are combined to create these highly efficient and reliable relays with as many as six poles or more.

These may have high voltage at the HV contact area. Safe high voltage procedures must be followed by personnel when close to any of these relays. Clearances and grounding rules must be observed.


Specifications are for reference only and are subject to change.
Contact Ross Engineering Corp. for current information.

High Voltage Relays