HP Modular Cooling System manual Glossary

Glossary

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/hr, 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 Modular Cooling System 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 of the
	cabinet or room. It can be water-to-water, water-to-air, or air-to-air configurations,
	in either direction.
Inrush current	The peak current flowing into a power supply the instant AC power is applied.
	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, 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 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	Maximum wattage of a given configuration, assuming worst-case conditions
consumption	(thermal tolerances, workloads, and so forth) on all system components. It is
	extremely unlikely that any customer will experience this level of power
	consumption.
True power	In an AC circuit, true power is the actual power consumed and is measured in
	watts. It is distinguished from apparent power by eliminating the reactive power
	component that might be present
Typical input current	The operating current of the product measured using a typical load and target
	voltage.

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