Static Switches


Input and output EMI filters
The STS unit supplies continuous power to critical loads from 2 separate AC supplies. while monitoring 2 input sources, if one of the input sources fails, the load is transferred to the other input source automatically. The user can perform transfer from one source to another using the manual transfer switch.

The main functions of the STS unit are as follows :
• Increased power quality
• Increased noise reduction
• Power blackout protection
• Power redundancy
• Automatic static switching
• Remote monitoring of input power sources
• Easy static and mechanical transfer between separate input sources
• Remote management of power events
• Power event logging
• Redundancy

Therefore inclusion of the Static Transfer Switches (STS) in an energy distribution system provides secure protection against any possible faults in the AC power system. STS permits switching between two independent AC power supplies (SOURCE 1 and SOURCE 2) without shutting down the critical load connected to its output.
STS is a microprocessor controlled transfer switch, designed for automatic and manual switching between two AC power sources, with interruption to the load of less than 2 msecs with synchronised sources and of less than 12 msecs for unsynchronised sources.

The STS utilises SCRs connected in opposite parallel pairs (six pairs for 6 pole models ,eight pairs for 4 pole models) . Three or four pairs of SCRs are used to connect the AC load to the power supply input referred to as “PREFERRED”, under normal conditions. The other three (of four) pairs of SCRs are on standby to transfer the load to the other power supply input referred to as “ALTERNATE” in case of a failure of the “PREFERRED” input supply.

Source 1 and Source 2 supply inputs should come from two different AC sources with nominally identical voltages, phases and frequencies. The aim of the STS is uninterrupted transfer from one AC power supply to the other, in case of a fault in the “PREFERRED” supply. Before and during transfer from one source to the other, the operating conditions of the SCRs are carefully monitored to prevent crosscurrents between two sources. The break-before-make technique makes healthy and
uninterrupted transfers possible.

During normal operation, “PREFERRED” network supplies the load when both inputs are available. Selection of the “PREFERRED” network, automatic re-transfer, re-transfer delay, overload behaviour of STS, alarm hold time, Non synchronised transfer behaviour, overload and transfer inhibit reset modes may be set by the user on the control panel of the unit.
Permitted voltage, phase difference and frequency tolerance are also adjustable by the service personnel on the control panel.

Basic Features:

• Increased power quality
• Easy monitoring all parameters on LCD display
• Fast micro controller (32 mips)
• Power blackout protection
• Automatic static switching
• Remote monitoring of input power sources
• Easy static and mechanical transfer between
separate input sources
• Remote management of power events
• Power event logging
• Advanced RS232 communication features
• DRY contact alarm interface
• Password protected login system from remote site
(time Access)
• 2 redundant power supplies for electronic boards
(hot swappable)
• Easy front access to all components inside of the
• Second protection cover on live circuits which
prevents electrical shock
• Input sources protected by fuses
• 3 positioned Maintenance bypass switch which
prevents cross currents between input sources
• User adjustable parameters by entering a password.
• Built in real time clock.
• Alarm history (with date and time)
• Automatic transfer test from a remote site or using
front panel
• Front panel Lamp test
• External emergency shut down (EPO) input
• Hot plug construction during maintenance bypass
• High current output tolerance up to 1000%
• Temperature sensor inside the Cabinet
• Fast voltage black-out circuit
• Input phase balance and phase sequence fault
detect circuit
• Adjustable Input source frequency lower/upper

A Manual Static Bypass Switch is also available for easy load transfer.

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