BES700 chapter 7

What does an uninterruptible power supply do?

An uninterruptible power supply (UPS) provides precise, unbroken AC power and protects against brown outs as well as blackouts. UPS is usually use for computers or other equipment that will not tolerate variations or interruptions in their input power. The normal flow of power is through a rectifier, a device that converts AC to DC, and into both the battery and the inverter, a device that converts DC to AC. If the AC input fit else, the DC power flows out of the battery and into the inverter which provides an AC Supply to the connected equipment.

In regard to light sources, what do the terms colour rendering index, colour temperature, and efficacy mean?

Colour rendering index is a unit of measure that defines how well colours are rendered by different illumination conditions in comparison to a standard such as daylight. It is calculated on a scale from 1 to 100 where 100 would be where all colour samples are illuminated. Colour temperature describe certain colour characteristics of light sources. It corresponds to the physical temperature of the blackbody radiator. Efficacy is the light produced measured in the units such as lumens divided by the energy input to the light measured in watts.

What are the maintenance issues with the building operator should address in the operation of electric monitors?

Face balanced and correct voltage can save 3 to 5% of motor energy and prolong the life of the motor, Clean motors will run cooler, last longer and use less energy, the primary contributor to motor failure is heat, Proper lubrication will maintain efficiency, Provide appropriate protection devices, Carry out regular mechanical and electrical diagnostics for larger motors.

What are the advantages of using compact fluorescent fixtures in place of incandescent fixtures?

Fluorescent fixtures are more energy efficient to operate than traditional incandescent light bulbs.

What is Peak demand and why is it important?

Maximum or Peak demand is maximum demand in kilowatts (kW) measured by the utility metre during a billing period. Peak demand is important because it is part of what is used to determine your monthly electrical bill.

In terms of electricity supply to the building, what do we mean by power and energy? What are the units of measure?

Power is the rate of electrical energy, in other words Powers how fast electrical energy is being used. It is measured in kilowatts (kW). Energy is the product of power over time, the sum of all the instantaneous power measurements during a period. It is measured in kilowatts per hour (kWh).

Transformer formula

Primary voltage/secondary voltage = No. of turns in primary coil/No. of turns in secondary coil.

What is power factor and why is it important?

Some tariffs, which are charges, include a power factor provision that scales up the billing demand if the facility power factor is less than a specific value, as well some terms may include a fuel adjustment charge to reflect the variability and primary fuel cost for power generation.

What measures should the building operator take to optimize efficiency of Lighting systems?

Switch off unnecessary lights, remove abundant fixtures, cleaning light fixtures, lamp reflectors and room services.

What would you expect the voltage to be in a typical building for single phase current? For a three-phase current?

The voltage between the ends of the Transformer is 240 volts in a single phase Supply thought the three phase current the voltage between two ends of the Transformer is only 208 volts, this is due to the phases being out of Step.

How can Energy Management Systems contribute to the efficient operation of buildings?

They can load shed, which means they turn off unnecessary things during High use periods, saving on power bills. They can use system scheduling, to turn on and off systems automatically. Optimize system, scheduling they can independently change due to variables such as light levels or outside temperature. Temperature setback, this is a fundamental technique for energy management. It sets temperatures in unoccupied spaces and during unoccupied hours to higher-than-normal set point during cooling season lower during the heating season.

What is the function of a Transformer? What is the basic principle of its operation?

Transformers of devices that change voltage, they are referred to as either step up or step down Transformers. In principle Transformers are quite simple devices that exploit a physical phenomena called induction. When two coils of wire wound around an iron core our side by side, and an alternating current is passed through one coil, a voltage is induced in the second coil. The input coil is referred to as a primary coil, and the output coil is a secondary coil. The second part of this induction penava is that the ratio of the number of turns in the primary coil to the number of turns in the secondary coil determines the ratio of primary to secondary voltage.