HIGH VOLTAGE ROTARY SWITCHES
Simple & Rugged Design
A key feature of our rotary switches is their simple mechanical design which results in conservative stress levels for trouble-free, long-life use. In addition, each rotary switch has a reinforced chassis design utilizing G-10 or G-11 fire retardant anti-tracking coated epoxy glass insulation. G-7 silicone glass is used for special applications where RF or high temperatures are involved.
Heavy duty contacts, specifically designed to minimize corona in the Ross rotaries, are made of highly conductive yet weld resistant alloy with high contact closing force. This high force gives our rotary switches high momentary current capability and a reputation for their ability to withstand high shock and vibration as well as other severe environmental conditions.
The Ross HV Rotary Switches can help engineers and specifiers meet OSHA and other safety organization regulations concerning protection for personnel from the danger of high voltage. To accomplish this, we design our rotary switches with manually or electrically operated actuators that include safety cam detent for positive contact positioning and safety interlocks.
Complementing this feature is a design concept unique to the Ross rotaries. We built our HV rotary switches with a SPDT auxiliary contact which is used as an interlock to protect an operator from "switching hot." This means during contact separation, power can be automatically shut off and interconnected systems can be made safe from accidental shorting due to arcing between poles. If additional protection is desired, our rotary switches can be designed with multiple SPDT auxiliary contacts and solenoid type locking devices.
The Ross HV Rotary Switches are used in a wide variety of applications worldwide. Among these are hipot voltage selectors, load and source selectors, power transformer tap changers, at either the high or low voltage end of transformer windings.
At RF levels, the higher current rotary switches can be used for tuning coil, alternate antenna, or dummy load selection.
High Voltage Rating
The Ross rotaries are built for 2kV to 450kV operation or more at 1mA to 200A or more continuous. All PK test voltages are 1 minute, 60Hz peak hold voltages in air unless otherwise noted. Ratings are for air at 760mmHg, 20ºC. Derate 3% per 1,000ft. above sea level. Voltage ratings can be doubled (or more) when used in oil or insulating gas.
For proper safety factor, PK test rating should be 1.2 to 5 times the normal circuit PK operating voltage, depending on applications. For lower power systems in air where transients are unlikely or moderate corona or intermittent flashover is of no consequence, a safety factor of 1.5 to 3 is desirable, and 2 to 3 is recommended. For higher power systems or where transient over-voltages are expected, and for minimum corona in air, a safety factor of 2.5 to 5 should be considered and the factor should be based on the maximum probable transient or impulse voltage requirement. The PK voltage to ground rating is similar to impulse ratings and should be selected in the same way as the contact to contact or pole to pole value. If a value other than the published rating is required, it can normally be supplied as an option, i.e., contact to contact or pole to pole voltages may be less than contact to ground, and size may be reduced.
When immersed in insulating oil, fluid or gas, the voltage withstand value is at least doubled and the interrupt capability is much greater. In a gas atmosphere, no modification is required. However, immersion in oil or fluid may require modifications in some cases, at extra cost (optional). For peak performance where high voltage is impressed directly across short lengths of solid insulation, increased length to prevent internal puncture at levels above the test rating in air may be required.
Current Rating DC to RF
Current ratings in air, as well as voltage ratings should be derated 3% per 1,000ft above sea level. Specified current ratings are continuous for 60Hz RMS and DC.
Some units can be used in RF applications, particularly those with G-7 silicone glass or steatite insulation, at reduced current ratings. All RF applications for these rotaries should be submitted to the Ross application engineers for review.
Epoxy Glass Insulation
G-10 or G-11 Epoxy glass laminate is standard insulation on most Ross HV rotaries. G-7 silicone glass insulation is recommended as an extra cost option for RF applications. Steatite insulation is used on some models. Extra lengths of insulation are available where high voltage contacts need to be spaced a greater distance from the actuator and interlock control circuit and ground.
Each unit is either manually or electrically operated. They are designed with a positive detent operating mechanism, with a low friction safety cam follower bearing. The cam detent feature allows positive contact positioning for greater safety when switch is in operation.
One SPDT auxiliary contact is standard on most units. The auxiliary contact is used as an interlock for protection against "Switching Hot" and accidental shorting due to arcing. They can also be designed with multiple SPDT auxiliary interlock contacts and/or solenoid type locking devices for extra safety. For in air use, most auxiliary contacts handle 250V to 480V, 15A, 60Hz or ½A, 125V DC.
Our oil-immersed units are built either with sealed, oil-resistant auxiliaries rated 5 to 7A maximum at 250V AC, or heavy duty open type contacts.
Mounting and Support
The Ross rotaries can be mounted in any attitude in either air, oil, fluid or gas atmosphere. Most units will withstand 10G or more shock. End support is recommended for longer units and high shock and vibration resistance.
Specifications are for reference only and are subject to change.
Contact Ross Engineering Corp. for current information.