A

Active Power

Alternate Current

B

Batteries

By-pass

Brownout

C

Charger

Continuous Current

COS Ø

D

Distortion:

E

Efficiency

Electronic Protections

G

I

IP

Input Current

In the case of a UPS, it’s the maximum effective (RMS) current drawn from mains. It is interesting to the selection of technical devices such as fuses and circuit breakers and for sizing of the cabinet.

Input Frequency

Number of times per second, that the mains supply voltage repeats its wave cycle. Cycle is called the shortest time when all the instantaneous values of the tension referred are met. The unit of measurement is Hertz (Hz) which corresponds to the number of cycles per second. The frequency of the network is maintained with tight tolerance around 50 Hz or 60 Hz (depending on the specification of the mains).

Input Voltage

RMS voltage value allowed at the entrance (the nominal value and upper and lower limits) that allows the equipment to work without changing performance.

Instant Current Limitation

When the loads consume high currents during the time they are connected, and / or on the peak of the sinusoidal wave, as is the case of computers, it must be provided for a short time all the energy that will be consumed until the next peak voltage. Because of this, the peak current could reach values that would be destructive to the UPS. However there is an electronic protection which limits the maximum instantaneous current, this current is several times the current that would be consumed by a resistive load such as an incandescent lamp.

Insulation

Inverter

It’s equipment that generates alternate voltage from a continuous voltage.

It’s used to power equipment using 230 V AC in fixed installations where the voltage supply is generally continuous, either to ensure continuity of supply in critical applications such as telecommunications, PABX, etc., or because the source of energy generates continuous voltage, as the applications of alternative energy such as wind and solar.
In mobile applications is used for, from a battery, for ex. a car, or boat, or bus battery, feed measuring equipment or other equipment such as videos, computers and electronic scales.

L

Limitation against Short Circuit

Limitation of Active Power

M

Mains Failure

There are several types of mains disturbances:

• Pulse (or peak) – momentary voltage increase (less than 1ms)
• Noise – pulses of oscillatory nature of high frequency.
• Micro power cut (or dropout) – total voltage loss between 1ms and 1s
• Power Cut (or outage) – total loss of voltage lasting longer than 1s
• Surge – Voltage surge over the nominal voltage longer than 2.5s
• Brownout – Voltage under the nominal voltage longer than 2.5s

Manual By-Pass

By-pass that is normally used for maintenance purposes, allowing the load to be powered by mains electricity when the UPS is off (ex.: For battery replacement, cleaning, etc.).
It can be found in units with or without static by-pass.

Mechanical Protection

The Index of Protection IP defines the protection of the equipment’s box.

The first number sets the maximum size of the body that can penetrate the box; the second defines its behaviour for liquids and the third number (seldom used), the impact energy.

First digit, protection against direct contact and external bodies input:

• 0 – no protection;
• 1 – against bodies greater than 50 mm (ex. unintended hand contact);
• 2 – against bodies greater than 12 mm (ex. fingers);
• 3 – against bodies greater than 2.5 mm (ex. tools, clips, hairpins);
• 4 – against bodies greater than 1 mm (ex. small wires);
• 5 – against harmful dust deposit;
• 6 – total protection against dust deposits.

Second digit, protection against liquids penetration:

• 0 – doesn’t have;
• 1 – against a vertical drop of water droplets (condensation);
• 2 – against falling drops to 15 degrees from the vertical;
• 3 – against falling drops to 60 degrees from the vertical (rain);
• 4 – against water projections in all directions;
• 5 – against high pressure water projections in all directions;
• 6 – against water projections equivalent to a wave;
• 7 – against immersion;
• 8 – submersible equipment in agreed conditions.

Third digit, impact energy of a body:

N

O

Output Current

In the case of a UPS, it’s the maximum effective (RMS) current that can be supplied to the load. This value is not usually specified, but instead the power in W or VA.

Output Frequency

Number of times per second, that the output voltage of a UPS repeats its wave cycle. The frequency of the output voltage is usually equal to the mains input voltage’s frequency. The tolerance of the output frequency depends on the equipment and is usually equal to 50 Hz (or 60 Hz) ± 1%.

In special cases, when the equipment to feed requires a different frequency from the one of the mains, you can use a UPS to generate the frequency output, and enable the use of such equipment.

Output Voltage

RMS value of the voltage generated by the equipment (nominal and tolerance) under various loading conditions (for ex., between 0 and 100% or only between 50 and 100%), with mains voltage and only with the battery voltage.

P

Power Factor

If the current of a load is sinusoidal and there is no gap between the voltage and current (as it’s the case of an incandescent lamp), the power consumed is given by the product (V x I in RMS).
If the current of a load is sinusoidal and there is mismatch between the voltage and current (as it’s the case of a fluorescent lamp), the power consumption is given by the product of voltage by apparent current consumption (the current that would measure a whether interclass ammeter), times the cosine of the lag angle Ø.

For example, if the current measure is 1A and the lag angle is 45°, which corresponds to a cos 45º = 0.707, so we have that Apparent Power is equal to:
A.P. = 230V x 1A = 230 VA
However, Active Power, i.e., the true power in watts, will be:
P = 230V x 1A x 0.707 = 162.6 W
If, for example, the load is the power supply of a computer, the power consumed is not sinusoidal, but in a pulsating in the crest of the sinusoidal. In this case it’s incorrect to speak of cos Ø, but in Power Factor.
Both cos Ø, whether the FP, are less than or equal to unity. This means that the smaller this value more is the current that must be provided for the same power consumption.
In the case of UPS, is typically considered a PF of 0.7 because computers present consumptions with a PF of this order, and may even reach 0.6.

R

Rectifier

Equipment that rectifies the voltage from the mains, i.e., transforms alternate voltage into continuous voltage. Although the terms rectifier, feeder and charger are sometimes used indiscriminately, as all these equipments rectifies mains voltage, the equipments are very different.

The term rectifier applies more properly to the devices used, for example, in electroplating, for currents that reach thousands of amperes without much demand for filtering (purity) of the supplied voltage.

Repetitive Peak Power

The loads that have switching power supplies, uses a pulsating current mode, only at the peak of the sine wave. UPS or Inverter must be able, during that short time, to provide all the energy that is consumed throughout all the half cycle. This peak current is much higher (about three times) that the current that would correspond to the same power if it was consumed in a sinusoidal mode, as in the case of an incandescent lamp.

The product of the peak voltage by the peak current, is called Repetitive Peak Power (since it is repeated every half cycle).

If the UPS does not have the ability to provide a high Repetitive Peak Power, the sinusoidal voltage is very low at the crest not feeding properly the load.

S

Safety

Any appliance must be harmless to the user. Nevertheless, its design must ensure safety standards that involve not only electrical aspects (eliminating the dangers of electrocution) as technical and mechanical (high temperatures, mechanical stability, etc.).

All these aspects are defined in safety standards, highlighting the IEC950.

Sine Wave

Wave whose form is a sine. The mains RMS voltage is 230 V AC and the peak value (voltage at the crest of the wave) is of 325 VAC.

Square Wave

It’s the most used and typical waveform used by off-line units. It has three levels of voltage (positive voltage, 0 volts and negative voltage). It is a wave economically and technologically easier to generate than a sine wave.

This waveform generates high frequencies (harmonics), which heats electric motors and transformers and does not hold generally the same relationship between the effective value (RMS) which should be 230 VAC and the peak value which should be 325 V.

This waveform, in order to confuse the consumer, receives from some manufacturers, a series of abusive names:

• Modified Sine Wave;
• Trapezoidal Wave;
• Pseudo-Sine Wave;
• PWM modulated Pseudo-Sine Wave
• Etc.

Stabilizer

It’s electronic or electromechanical equipment (with a varying motor, in this case) to correct deviations, surges and sags of the mains voltage in relation to the nominal value.

Static By-Pass

This is a By-Pass that uses solid state devices (Thyristors, Triacs and Transistors) for power transfer. In a UPS is used to increase overall reliability of the equipment, providing power to the load by mains, in the event of failure of the Inverter or violent overflow. Depending on the construction, the transfer between the inverter and the mains is done without interruption.

Surge

Switching

This word means in everyday language, a technology used in power converters.
To transfer power through a transformer, it can run on the mains frequency (50 Hz or 60 Hz) or at a high-frequency, ex. upper than 20.000 Hz (20 kHz) using electronic devices to get this high frequency.
The advantages of this technology are the small size and weight, the silence (the acoustic noise it generates is inaudible) and its low cost.
The disadvantage is the higher complexity of the project.

T

Thermal Protection

Electronic or mechanical device (thermostat) to protect equipment in case of over temperature (fan damaged or blocked air vents, high ambient temperature, etc.).

For protection normally acts switching off the equipment.

Transfer Time

In the case of off-line units, it’s the time between a mains failure and the replacement of the output voltage generated by the inverter.

Should be taken into account the time of detection of mains failure coupled with the switching time of the used device (relay or other).

The opposite case, passage of the inverter to the mains is less critical.

For on-line units with by-pass the transfer time is zero, since the switching between the inverter and the mains, and vice versa, is provided by solid state components (Thyristors), which switching is, to all practical purposes, instantaneous.

U