400V 25-1000A 1/2/3/4-pole

Static Transfer Switches (STS) are designed to transfer the supply between two independent A/C power sources. Unlike traditional automatic transfer switches (ATS), a static transfer switch provides a fast load transfer (typically ¼ of a cycle), which ensures uninterruptible operation of sensitive electronic equipment. Load retransfer to the preferred input source is virtually instantaneous (typically 0.1ms). The basic applications of STS are in automatic systems in the power industry, power supply systems for petrochemical industry, computer and telecommunications centers, automatic and security systems of ‘intelligent’ buildings as well as other equipment which is sensitive to interruptions in the supply. The excellent overload capability in the event of a short-circuit. As a consequence the voltage immediately returns to normal to supply the other loads. The built-in transient voltage surge suppression system for SCR switches provides additional protection against damage to the supplied equipment.

The static transfer switch consists of two bidirectional thyristor switches for each phase equipped with a control and protection system. The 2 or 4 pole types have an additional neutral line switch. After failure of the preferred source, the STS checks the state of the alternate power sources and transfers the load whichever sources provides power within selectable limits. This transfer can be triggered by disturbance in the preferred sources voltage, over current in the sources or manual or remote change of the preferred source. With both sources in limits and synchronized (phase error within the acceptable range), manual or remote transfer is performed in less than 200 us. Transfers initiated by fault conditions in the preferred sources depend on the status of the alternate source. For synchronized power sources with phase error within limits, transfer to an alternate sources is made within 6ms delay. Lack of synchronization causes delay before transfer. It is possible to set delay before transfer. It possible to set the delay with dipswitches.