HP Modular Cooling System Installationshandbuch PDF herunterladen (Seite 58)

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

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.

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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