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Description
SMC medium voltage metal-clad switchgear is an integrated assembly of drawout vacuum
circuit breakers, bus, protective, and control devices which are coordinated electrically
and mechanically for medium voltage distribution and protection. The metal-clad
construction provides maximum circuit separation and safety. This is accomplished by
grounded metal compartment barriers and insulated conductors. These features are
combined so that no live parts are exposed by opening of the doors.
SMC metal-clad switchgear offers the benefits of vacuum interrupters -- high
reliability, low maintenance, and reduced weight. It is typically used for
transformer and large motor feeder circuits.
Features
Metal-Clad switchgear is an assembly of components characterized by the following
features:
 | The main circuit interrupting device is removeable and is arrange with a mechanism for
moving it between the connected and disconnected positions. It is equipped with
self-aligning and self-coupling primary and secondary devices. |
| The interrupting devices, buses, voltage transformers and control power transformers are
completely enclosed by grounded metal barriers, which have no intentional openings between
compartments. A metal barrier in front of the interrupting device ensures that no live
parts are exposed by the opening of a door, when in a connected position. |
| Automatic shutters cover the primary disconnects when the removable element is removed
or in the test or disconnected positions. |
| All live parts are enclosed within grounded metal barriers and separated into individual
compartments by voltage level. Instruments, meters, relays, secondary control
devices and their wiring are isolated from all primary circuit elements by grounded metal
barriers. |
| Primary bus conductors and connections are covered with tract-resistant insulation. |
| Mechanical interlocks are provided to insure proper and safe operation. The
circuit breaker cannot be racked to or from the connected position with its contacts
closed nor can it be removed from the enclosure with the stored energy mechanism charged. |
Applicable Industry Standards*
ANSI -- American National Standards Institute:
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| C37.010 |
Application Guide for AC High-Voltage Circuit Breakers Rated
on a Symmetrical Current Basis |
| C37.100 |
Definitions for Power Switchgear |
| C37.04 |
Rating Structure for High-Voltage Circuit Breakers |
| C37.06 |
Preferred Ratings for AC High-Voltage Circuit Breakers |
| C37.07 |
Factors for Reclosing Service |
| C37.09 |
Test Procedures for AC High-Voltage Circuit Breakers |
| C37.11 |
Power Circuit Breaker Control |
| C37.20.2 |
Metal Clad and Station Cubicle Switchgear |
| C37.21 |
Application Guide for Metal Enclosed Switchgear |
| C37.55 |
Conformance Testing of Metal-Clad Switchgear |
NEMA -- National Electrical Manufacturers Association
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| SG-4 |
Power Circuit Breakers |
| SG-5 |
Power Switchgear |
* Can be manufactured to meet the requirements of other standards.
Stacking Arrangment
| 1200A Breaker |
1200A Breaker |
Aux. |
1200A Breaker |
2000A Breaker |
2000A Breaker |
Aux. |
2000A Breaker |
Vented Aux.
Note 2 |
| 1200A Breaker |
Aux. |
1200A Breaker |
2000A Breaker |
1200A Breaker |
2000A Breaker |
2000A Breaker |
Aux. |
3000A Breaker |
Notes:
- Main bus sizes: 1200A, 2000A, 3000A, or 3750A
- No rollout auxiliaries allowed in the same vertical section as a 3000A breaker
- Auxiliary cells may contain two rollout
- Fused rollouts for stationary control power transformer (CPT) must be located in lower
rollout position in lower auxiliary cell.
- Stacking arrangements are available as shown. Total circuit reaker loading in a
vertical unit may not exceed the main bus rating. Consult factory for specific
application assistance regarding total load limits in each unit.
- Any position may be left blank.
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1200A or 2000A / 1200A or 2000A Breaker
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Auxialiary / 1200A or 2000A Breaker
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Auxiliary/Auxiliary
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Blank / 3000A Breaker
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Type GMI Circuit Breaker Ratings
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 PDF Document
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Drawout Circuit Breaker Element
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For SMC Power Systems Operation
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