English
русский
Español
Deutsch
The SC-68/3A is a dedicated rotary changeover switch designed for current measurement in three-phase AC systems, commonly referred to as an "ammeter phase-changing switch" or "current selection switch." Its core function is to safely and conveniently connect an ammeter to any phase (R-phase, S-phase, or T-phase) of a three-phase circuit by rotating the handle, monitoring the current in each phase. Alternatively, in the "0" position, the ammeter can be completely disconnected from the circuit being measured, achieving "one meter for three phases."
Rated operating current: 20A (refers to the continuous current-carrying capacity of the switch's main circuit contacts, matched to the current of the circuit being measured)
Rated operating voltage: ≤ 600V AC
Rated insulation voltage: 690V
Power frequency: 50Hz ~ 60Hz
Structure and contact configuration:
Structure: Three-section (three-layer) structure, each layer independently corresponding to the switching of one phase current.
Positions and functions:
Position "0" (OFF): All contacts are open, the ammeter is completely isolated from the circuit being measured, and is in a safe state.
Position "R": Connect the ammeter to the R-phase current loop to measure the R-phase current.
Position "S": Connect the ammeter to the S-phase current loop to measure the S-phase current.
Position "T": Connect the ammeter to the T-phase current loop to measure the T-phase current.
Key Design: The internal structure employs a special design, such as a pre-connection followed by a disconnection or a short-circuit loop connection, to ensure that the secondary side of the current transformer (CT) does not open-circuit during switching, thereby avoiding dangerous high voltage and ensuring equipment and personnel safety.
Materials and Safety:
Contacts: Use highly conductive materials such as silver alloy to ensure reliable measurement contact.
Insulation and Housing: Uses high-insulation-strength materials (insulation voltage 690V), with a robust structure to prevent short circuits.
Markings: The panel is clearly marked with "0, R, S, T" positions for intuitive operation.
Application Scenarios
This switch is a standard accessory for current monitoring in three-phase power systems, primarily used in the following applications:
Distribution Cabinets/Panels: Installed on the panel of low-voltage distribution cabinets, power boxes, and capacitor compensation cabinets, it works in conjunction with current transformers (CTs) and ammeters to facilitate maintenance personnel in checking the balance of three-phase currents during inspections.
Motor Control Centers (MCCs): Used to monitor the three-phase operating current of large motors or important loads, determining if the motor is overloaded or experiencing phase loss.
Generator Control Panels: Monitors the current of each phase at the generator output.
Industrial Equipment Control Boxes: Used in any electrical control equipment requiring monitoring of three-phase power current, saving on instrument costs and simplifying panel layout.
Core Value: Enables safe and sequential monitoring of three-phase current using a single ammeter, a common and economical solution for electrical system monitoring.
