Skip to main content

STANDARD REQUIREMENTS IN DEALING WITH VOLTAGE TRANSFORMERS

STANDARD REQUIREMENTS IN DEALING WITH VOLTAGE TRANSFORMERS
What is a Voltage Transformer with respect to C57.13?

Terms in which ratings shall be expressed
The ratings of a voltage transformer shall include:
     a) Basic impulse insulation level in terms of full-wave test voltage
     b) Rated primary voltage and ratio
     c) Frequency (in Hertz)
     d) Accuracy ratings
     e) Thermal burden rating

Standard burdens
Standard burdens for voltage transformers for rating purposes are shown in table below.

burden for Voltage transformer

Assignment of accuracy ratings
A voltage transformer shall be assigned an accuracy rating for each of the standard burdens for which it is rated. For example, an accuracy rating might be 0.3W and X, 0.6Y, 1.2Z.
Accuracy classification for voltage transformers with two secondary windings or tappedsecondary windings - The burden on any two secondary terminals affects the accuracy on all other terminals. The burden stated in the accuracy ratings is the total burden on the transformer. The accuracy class shall apply with the burden divided betweenthe secondary outputs in any manner.

Thermal burden ratings
The thermal burden rating of a voltage transformer shall be specified in terms of the maximum burden in voltamperes that the transformer can carry at rated secondary voltage without exceeding the temperature rise. If no thermal burden in voltamperes rating is given, the thermal burden rating in voltamperes shall be the same as the maximum standard burden for which an accuracy rating is given.

Each winding, including the primary winding, of a multiple-secondary transformer shall be given a thermal burden rating. If only one thermal burden rating is specified, it shall be applicable to any distribution of secondary voltamperes, including the use of taps.

Nameplates
Voltage transformers shall be provided with nameplates that shall include, as a minimum, the following information:
     a) Manufacturer's name or trademark
     b) Manufacturer's type
     c) Manufacturer's serial number (SER), numerals only
     d) Rated voltage (PRI)
     e) Ratio or ratios
     f) Basic impulse insulation level (BIL kV)
     g) Rated frequency (in Hertz)
    h) Thermal burden rating or ratings at ambient temperature or temperatures, in voltamperes in degrees Celsius
    i) Accuracy rating: maximum standard burden at which the accuracy rating is 0.3 class, as a minimum.

Terminals
Primary terminals shall be electrically and mechanically suitable for use with either copper or aluminum conductors. Secondary terminals shall be electrically and mechanically suitable for use with copper conductors.
Labels:

Comments

Post a Comment

Popular posts from this blog

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.
50 comments
click here to continue

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
5 comments
click here to continue

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").
43 comments
click here to continue