The main focus of power quality susceptibility is the notion of keeping the ICT equipment up and running in spite of “dirty” power. For this, the power supply units (PSU’s) of the ICT kit need to operate in spite of less than perfect power quality.
The figure shown here is a simplified block diagram of an ICT equipment power supply. The input AC voltage is stepped down by a transformer and then rectified and filtered to produce the DC voltage rails on which the server electronics (here shown as the “load”) operates.
Power supplies can “ride- through” voltage disturbances. How well they do this depends upon how they’re designed and also upon the system in which they’re operating.
The ride-through ability of server power supplies has been compromised as of late in favor of things like cost, reduced form factors, and a growing focus on energy efficiency. These will have impacts on the ability to ride through certain input power quality disturbances.
In any case, the specification for how the ICT equipment can ride through power quality degradations is assumed to be described by the ITIC/CBEMA curve. Because the power supply unit is the component of the ICT equipment which receives and reacts to the input power, it is the main focus of application of the ITIC/CBEMA curve to the ability for contemporary ICT equipment to tolerate power quality disturbances.
By Bob Landstrom
(This is Part-4 of a 9-part series on a contemporary assessment of the ITIC/CBEMA curves)