HP Modular Cooling System Generation 2 site preparation guide - Technical white paper

48
Appendix C: glossary
Table 15 lists technical terms and abbreviations used in this guide.
Table 15: Terms and abbreviations
Term
Description
Apparent power
A value of power for AC circuits that is calculated as the product of RMS current
times RMS voltage, without taking the power factor into account
ASL
Above sea level
BTU/hr
British thermal units per hour; the amount of heat required to raise one pound of
water 1°F/hour, a common measure of heat transfer rate
CFM
Cubic feet per minute, commonly used to measure the rate of air flow in an
air-conditioning system
Chilled water system
A type of air-conditioning system that has no refrigerant in the unit itself. The
refrigerant is contained in a chiller, which is located remotely. The chiller cools
water, which is piped to the air conditioner or HP MCS to cool the space.
Derate
To lower the rated capability of an electrical or mechanical apparatus
Heat exchanger
Cooling unit that maintains two separate environments inside and outside the
cabinet or room. It can be either a water-to-water, water-to-air, or air-to-air
configuration, in either direction.
Inrush current
The peak current flowing into a power supply the instant AC power is applied
to. This peak is usually much higher than the typical input current because of the
charging of the input filter capacitors. When switching power supplies are first
turned on, they present high initial currents as a result of filter capacitor
impedance. These large filter capacitors act like a short circuit, producing an
immediate inrush surge current with a fast rise time. The peak inrush current can
be several orders of magnitude greater than the supply’s typical current.
Leakage current
A term relating to current flowing between the AC supply wires and earth
ground. The term does not necessarily denote a fault condition. In power
supplies, leakage current usually refers to the 60 Hz current, which flows
through the EMI filter capacitors that are connected between the AC lines
and ground.
Maximum input current
The operating current of the product equal to the maximum load divided by the
minimum input voltage
Power factor
The ratio of true power (watts) to apparent power (VA) in an AC circuit. In
power conversion technology, the power factor is used in conjunction with
describing the AC input current to the power supply.
RMS
Root-mean-square. Term that refers to the most common mathematical method of
defining the effective voltage or current of an AC wave. To determine the RMS
value, three mathematical operations are carried out on the function
representing the AC waveform:
(1) The square of the waveform function (usually a sine wave) is determined.
(2) The function resulting from step 1 is averaged over time.
(3) The square root of the function resulting from step 2 is found.
Theoretical maximum power
consumption
Maximum wattage of a given configuration, assuming worst-case conditions
(thermal tolerances, workloads, and so forth) on all system components. It is
extremely unlikely that any customer will experience this level of power
consumption.