Issue:
Does the Symmetra LX offer surge protection?

Product:
Symmetra LX

Environment:
Symmetra LX

Answer:

The Symmetra LX was surge tested with 6,000 volts and a maximum of 500 amps without dropping the load. The topology used in the Symmetra UPS's is Double online conversion. In Double Online Conversion, the power is always filtered since it passes through a rectifier then to the charger. The charger then feeds the battery where the battery then feeds an inverter which then converts DC battery power to AC Voltage used to feed the load. Meaning, there will be no means that a surge or any power irregularity will pass to the load "while the unit is at an online state". More details on Double Online Conversion also is discussed in page 7 of APC by Schneider Electric White Paper # 1.

In a Symmetra LX, the SYPM4KP / SYPM4KI power modules and the SYAFSU13 / SYAFSU13I slide tray would have some basic surge protection of "its own" to help protect the LX frame and clamp down on any surges before even reaching the rectifier. The rectifiers can fail open or sacrifice themselves out in the event that the surge is too strong. If this happens, there will be no power passing to the load and it would shutdown everything and again will prevent any unwanted surge from reaching the equipment supported by the UPS. This is as long as the unit is "online" when it gets hit by a surge.

Symmetra LX units however has static bypass functions which can be issued through the Power View Display, NMC, Dry Contacts, Software or by Physical means. While online and the unit experiences a surge "from the input", the bypass will not immediately engage especially if the "power input" is not within spec of what has been set to the unit. The intelligence modules watches the power feed from all the power modules to make certain it is up to spec. Please do bear in mind though that the Symmetra units main purpose with its bypass is to not drop the load hence why Double Conversion units share a common term "fault tolerant UPS units". This means that on faults, low battery conditions, out of spec "output" waveform (caused by failing power supplies from the load or extremely inductive loads), and/or the unit goes to a true overload state, the unit will automatically engage to temporary/soft bypass as long as the input power is within spec. However, when the unit enters bypass, the rectifier and inverter turns both off and the load will be left unprotected since there is no longer any filtering being done at this state and there is no direct connection to the battery

IMPORTANT NOTE : If concerns on possible damage to the LX from surges are raised, it is recommended to install an upstream SPD (Surge Protection Device) with a rating smaller than the testing values stated above. It is also good to note that these units is to be placed on locations where careful planning on cooling and or power distribution is made prior to UPS installation.

Should there be any other questions, feel free to reach out to us at 800-800-4272 or our chat support group at APC by Schneider Electric Customer Technical Support

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