TERMS DEFINITION

Before we discuss on any of the previously stated factor, let us first define some important terms the we should be familiar with:

LOAD GRAPH/CURVE - is a graphic record showing the power demands for every instant during a certain time interval. The area under the load curve is equal to the energy or kW-hr delivered to the particular load.

CONNECTED LOAD - The connected load on any system or part of the system is the combined continuous rating of all the receiving apparatus on the consumer's premises that is connected to the system under consideration.

DEMAND - it is the load usually expressed in kW, kVA averaged over a suitable and specified interval of time of short duration.

MAXIMUM DEMAND or PEAK LOAD - is the greatest of all the demands that have occurred during a given period. It is measured according to specifications, over a prescribed time interval during a certain period such as a day, a month, a year.

AVERAGE LOAD - it is defined as the average demand during a certain period of time. Utilities usually computes average load in monthly basis. So that is the sum of all daily peak demands divided by the total number of days.

(Rafael D. Seva Jr.)

KILOWATT (kW) – also referred to as the useful power or the true power. This is the power needed to operate a certain electrical device or apparatus.

KILO-VOLT-AMPERE REACTIVE (kVAR) – also referred to as the phantom power and reactive power.

KILO VOLT-AMPERE – also referred to as the apparent power. This is the power required to be drawn from the source.

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PARTS OF A POWER TRANSFORMER

What are the name of the basic parts of a Power Transformer? We can not deny the fact that only a handful of electrical engineering students are presently familiar with power transformers especially on what it looks like. Unlike a transformer we found in our homes, a power transformer’s appearance and construction is somewhat more complicated. It is not just a simple winding with a primary and secondary terminal although basically any transformer has one. The function that a power transformer plays in an electrical system is very important that an electric utility can not afford to loss it during its operation. Our discussion here will focus more on the basic parts and functions of a power transformer that are usually tangible whenever you go to a substation . Although not all power transformers are identical, nonetheless they all have the following listed parts in which the way of construction may differ.

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ELECTRIC MOTOR FRAME SIZE STANDARD SPECIFICATIONS

ELECTRIC MOTOR FRAME SIZE STANDARD SPECIFICATIONS How is electric motor frame size being specified? Motor frame dimensions have been standardized with a uniform frame size numbering system. This system was developed by NEMA and specific frame sizes have been assigned to standard motor ratings based on enclosure, horsepower and speed. The current standardized frames for integral horsepower induction motors ranges from 143T to 445T. These standards cover most motors in the range of one through two hundred horsepower. Typical example of where you can locate the frame is shown in Fig 1.2.D – Frame No. The numbers used to designate frame sizes have specific meanings based on the physical size of the motor. Some digits are related to the motor shaft height and the remaining digit or digits relate to the length of the motor. The rerate, or frame size reduction programs were brought about by advancements in motor technology relating mainly to higher temperature ratings of insulating mate

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ELECTRIC MOTOR NAMEPLATE SPECIFICATIONS

How do we interpret an electric motor nameplate? Motor standards are established on a country by country basis.Fortunately though, the standards can be grouped into two major categories: NEMA and IEC (and its derivatives). In North America, the National Electric Manufacturers Association (NEMA) sets motor standards, including what should go on the nameplate (NEMA Standard MG 1-10.40 "Nameplate Marking for Medium Single-Phase and Polyphase Induction Motors").

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