3 Phase Static Transfer Switch
The STS is built with two independent power inlets. The load normally runs from the primary source. If the primary source fails, the secondary source...
View SpecificationsThe Problem With Two Feeds And No Switch
Many sites already pay for two supplies. Without an automatic switch the load sits on one of them, and a fault on that feed takes the load down while the second supply sits idle a few metres away.
How The Transfer Actually Happens
The switch has two independent inlets. Source A is the priority input. When source A fails, SCR devices disconnect it and connect source B, first disconnect then connect, so the two sources are never bridged. Typical transfer time is 6 ms or less.
3 Phase Static Transfer Switch
Why Six Milliseconds Matters
A switch mode power supply of the kind used in servers and controllers holds its output through a short interruption. A transfer inside that window is invisible to the load. A mechanical changeover taking tens or hundreds of milliseconds is not.
Sizing And Selection
Ratings run from 63 A to 400 A per phase at 3 phase 380 V. Select on measured per phase current. Above 45 degrees C ambient or 1500 m altitude the unit has to be derated.
What It Does Not Do
A transfer switch selects between sources. If both sources fail there is no energy left to switch to, so a site that needs ride through still needs a UPS or generator behind it.
Equipment In This Guide
Products Referenced Above
FAQ
Questions Buyers Ask
Is a static transfer switch the same as an ATS?
No. A mechanical ATS uses moving contacts and transfers in tens or hundreds of milliseconds. A static transfer switch uses SCR devices and transfers in 6 ms or less.
Does the switch improve power quality?
It selects a source. Voltage and frequency conditioning is the job of a converter or a UPS.
Check Your Case With An Engineer
Send the numbers from your own site and we will tell you which model the guide points to.