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Waveform: Stepped Approximation/Pure Sine Wave

Issue

Waveforms for PS, AS, and I/O modules

Environment

SmartStruxure Site

Cause

Loss of power and UPS for the StruxureWare Building Operation and SmartStruxure product lines.

Should you design a site with Stepped Approximation or Pure Sine Wave?

Resolution

Concerning the UPS, and in particular the APC UPS 650, this is a good UPS, but the problem is that it would still interrupt the power for enough time to reset the AS. The AS has a 100mS capacity. Lessons Learned article 7229 has a bit more information would be beneficial to read through.

A good UPS would be one that is Online or sometimes referred to as Double Online. This means that the power is not interrupted. The APC UPS line that has this is the SmartUPS and the base model is the old 1000XLI. This model may or may not be available in every country, but there would be a comparable model available. APC has been replacing the 1000XLI with various models, but all have the capability to go directly to battery, then back to power once the power is restored (assuming that there is a backup generator or the main power is restored) before the battery is pulled down.

The Automation Server is powered from one or several PS-24V units. They have and peak voltage rectification on the input and the voltage waveform should not be an issue as long as the peak voltage is similar to that of a sine wave. If the input voltage is increasing with a very high dV/dt there may be high input current peaks. Those peaks may but not necessarily be reduced by the 230/24V transformer.
 

Key Concept: Look for a model with the Topology of Line Interactive and the Waveform Type of Sine wave.

Picture is simply for example but not required:

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