Thursday, February 27, 2014
Tuesday, February 25, 2014
Terms AC1 and AC3
AC-1 - This category applies to all AC loads where the power factor is more than 0.95. These are primarily non-inductive or slightly inductive loads, such as heating. Breaking the arc remains easy with minimal arcing and contact wear.
AC-3 - This category applies to squirrel cage motors with breaking during normal running of the motor.
On closing, the contactor makes the inrush current, which is about 5 to 7 times the rated full load current of the motor.
On opening, the contactor breaks the rated full load current of the motor.
Monday, February 24, 2014
Cross Reference (Approximate) NEMA, UL, CSA, vs. IEC Enclosure Type
(Cannot be used to convert IEC Classifications to NEMA Type numbers)
Thursday, February 20, 2014
Understanding Type 2 Coordinated Protection in Motor Branch Circuits
The new IEC (International Electrotechnical Commission) standard, publication
947 “Low Voltage Switchgear and Control, Part 4-1: Contactors and Motor Starters,”
has been recognized by UL (Underwriters Laboratories) and is becoming
widely accepted by designers and users of motor control in the U.S. This standard
addresses coordination between the branch circuit protective device and the motor
starter. It also provides a method to measure performance of these devices if a short
circuit occurs. This standard defines two levels of component protection in the
event of a short circuit: Type 1 and Type 2 coordination.
This Product Data Bulletin describes:
_ How to conformto the new standard using motor controls built to meet
NEMA and IEC standards
_ Related benefits associated with Type 2 coordination
The IEC standard for motor starters and contactors, 947-4-1, defines two levels of
protection/coordination for the motor starter (contactor and overload relay) under
short circuit conditions. Each level of protection is achieved by using a specific
combination of motor starter and short circuit protective device.
_ Type 1 Coordination
Under short circuit conditions, the contactor or starter shall cause no danger
to persons or installation and may not be suitable for further service
without repair and replacement of parts.
_ Type 2 Coordination
Under short circuit conditions, the contactor or starter shall cause no danger
to persons or installation and shall be suitable for further use. The risk
of contact welding is recognized, in which case the manufacturer shall indicate
the measures to be taken in regards to equipment maintenance.
Faults in electrical systems are most likely to be of a low level, which are handled
well by motor controllers built to meet Type 1 coordination standards. After the
fault is cleared, the only action necessary is to reset the circuit breaker or replace
the fuses. In situations where available fault currents are high and any period of
maintenance downtime is crucial, a higher degree of coordinated protection may
be desirable.
Many industries are dependent upon the continuous operation of a critical manufacturing
process. In these conditions, it is especially important to understand that
Type 1 protection may not prevent damage to the motor starter components. In order
to ensure that high level fault or short circuit does not interrupt a critical process,
it may be prudent to consider implementation of Type 2 coordination in the
selection and application of low voltage motor controllers.
Type 2 coordination, which has no equivalent U.S. standard, does not permit damage
to the starter beyond light contactwelding, easily separated by a screwdriver or several
coil operations. Type 2 coordination does not allowreplacement of parts (except fus-
es) and requires that all parts remain in service. Beyond providing basic electrical and
fire protection, it also minimizes lost production, reduced productivity and unscheduled
disruptions resulting fromdowntime needed to replace or repair a starter.
SQUARE D Product Data Bulletin
Why Are Copper Bus Bars Plated?
Even though copper is the most popular choice for use in bus bars, and used very often in other electrical applications because it is more resistant to rust and corrosion than other metals, this doesn’t mean that it won’t oxidize over time.
When metals oxidize, the resistance in the conductive metal will increase, requiring more power to be used to carry current along the surface. When the copper oxidizes beyond a certain point, the metal can begin to flake and fall apart.
Many metals are plated in order to help them retain their positive qualities and attributes. When it comes to copper bus bars, plating is an important factor in longevity as well as maintaining the integrity of the conductive surface. When copper bus bars are not plated, over time the surface will oxidize. When that occurs, then more power is required to push electricity along the surface because the oxidized surface simply doesn’t conduct as well as a smooth, plated surface.
Plating, using tin or silver acts as a coating over the surface of the copper, helps to protect the copper from oxidizing. While this will not completely prevent oxidizing over a long period of time, it will dramatically reduce the effects of such oxidization. The reason why tin and silver is commonly used in the plating technique for copper is that both metals are considered soft metals, easier to work with when plating, and more importantly they don’t offer a great deal of resistance to electrical conductivity.
Which is better? Tin or Silver?
Throughout the industry there are different thoughts about which metal is better for plating copper, tin or silver. 10 microns of tin will outperform 1 micron of silver. With the price of silver climbing, tin becomes more economical, even though ten times the amount of tin will be required to do the same job.
When using silver to plate copper bus bars, a minimum of 3 microns should be used, and preferable 6 microns. On top of that, an anti-tarnish would need to be applied as well to protect the finish. In most fixed bus bar applications, tin is recommended. Silver should be used for moving bus bar parts in which arcing may be a concern.
For both tin and silver plating, anti-tarnish is important to keep the surface clean and conductive. When working with copper bus bars, plating is essential not only for longevity, but also integrity and safety.
Copyright :
http://blog.prv-engineering.co.uk/2012/05/why-are-copper-bus-bars-plated/
Wednesday, February 19, 2014
CE marking
The CE marking indicates a product’s compliance with EU legislation and so enables the free movement of products within the European market. By affixing the CE marking to a product, a manufacturer declares, on his sole responsibility, that the product meets all the legal requirements for the CE marking, which means that the product can be sold throughout the European Economic Area (EEA, the 28 Member States of the EU and European Free Trade Association (EFTA) countries Iceland, Norway, Liechtenstein). This also applies to products made in other countries which are sold in the EEA.
However, not all products must bear the CE marking, only product categories mentioned in specific EU directives on the CE marking.
CE marking does not indicate that a product was made in the EEA, but merely states that the product has been assessed before being placed on the market and thus satisfies the applicable legislative requirements (e.g. a harmonized level of safety) enabling it to be sold there. It means that the manufacturer has:
verified that the product complies with all relevant essential requirements (e.g. health and safety or environmental requirements) laid down in the applicable directive(s) and
if stipulated in the directive(s), had it examined by an independent conformity assessment body.
It is the manufacturer’s responsibility to carry out the conformity assessment, to set up the technical file, to issue the declaration of conformity and to affix the CE marking to a product. Distributors must check that the product bears the CE marking and that the requisite supporting documentation is in order. If the product is being imported from outside the EEA, the importer has to verify that the manufacturer has undertaken the necessary steps and that the documentation is available upon request.
Copyright CE-Marking
IEC 60364 Electrical Installations for Buildings
IEC 60364 Electrical Installations for Buildings is the International Electro technical Commission's international standard on electrical installations of buildings. This standard is an attempt to harmonize national wiring standards in an IEC standard. The latest versions of many European wiring regulations (e.g., BS 7671 in the UK) follow the section structure of IEC 60364 very closely, but contain additional language to cater for historic national practice and to simplify field use and determination of compliance by electrical tradesmen and inspectors. National codes and site guides are meant to attain the common objectives of IEC 60364, and provide rules in a form that allows for guidance of persons installing and inspecting electrical systems.
The standard has several parts:
Part 1: Fundamental principles, assessment of general characteristics, definitions
Part 4: Protection for safety
Section 41: Protection against electric shock
Section 42: Protection against thermal effects
Section 43: Protection against overcurrent
Section 44: Protection against voltage disturbances and electromagnetic disturbances
Part 5: Selection and erection of electrical equipment
Section 51: Common rules
Section 52: Wiring systems
Section 53: Isolation, switching and control
Section 54: Earthing arrangements, protective conductors and protective bonding conductors
Section 55: Other equipment
Section 56: Safety services
Part 6: Verification
Part 7: Requirements for special installations or locations
Section 701: Electrical installations in bathrooms
Section 702: Swimming pools and other basins
Section 703: Rooms and cabins containing sauna heaters
Section 704: Construction and demolition site installations
Section 705: Electrical installations of agricultural and horticultural premises
Section 706: Restrictive conductive locations
Section 708: Electrical installations in caravan parks and caravans
Section 709: Marinas and pleasure craft
Section 710: Medical locations
Section 712: Solar photovoltaic (PV) power supply systems
Section 713: Furniture
Section 714: External lighting
Section 715: Extra-low-voltage lighting installations
Section 717: Mobile or transportable units
Section 740: Temporary electrical installations for structures, amusement devices and booths at fairgrounds, amusement parks and circuses
Wikipedia
Welding standards (ISO)
International Organization for Standardization (ISO) has developed over 18500 standards and over 1100 new standards are published every year. The following is a partial list of the standards specific to welding:
Standard Number Description
ISO 2553 Welded, brazed and soldered joints - symbolic representation on drawings (1992)
ISO 2560 Welding consumables. Covered electrodes for manual metal arc welding of non-alloy and fine grain steels. Classification
ISO 3580 Covered electrodes for manual arc welding of creep-resisting steels - Code of symbols for identification
ISO 3581 Covered electrodes for manual arc welding of stainless and other similar high alloy steels - Code of symbols for identification
ISO 3834 Quality requirements for fusion welding of metallic materials, five parts.
ISO 4063 Welding and allied processes - Nomenclature of processes and reference numbers
ISO 5817 Welding. Fusion-welded joints in steel, nickel, titanium and their alloys (beam welding excluded). Quality levels for imperfections
ISO 6520-1 Welding and allied processes — Classification of geometric imperfections in metallic materials — Part 1: Fusion welding
ISO 6520-2 Welding and allied processes — Classification of geometric imperfections in metallic materials — Part 2: Welding with pressure
ISO 6947 Welds. Working positions. Definitions of angles of slope and rotation
ISO 9606 Qualification test of welders — Fusion welding, parts 1 to 5
ISO 9692-1 Welding and allied processes. Recommendations for joint preparation. Manual metal-arc welding, gas-shielded metal-arc welding, gas welding, TIG welding and beam welding of steels
ISO 9692-2 Welding and allied processes. Joint preparation. Submerged arc welding of steels
ISO 9692-3 Welding and allied processes. Joint preparation. Part 3: TIG and MIG welding of aluminium and its alloys
ISO 13847 Petroleum and natural gas industries - Pipeline transportation systems - Welding of pipelines
ISO 13916 Welding - Guidance on the measurement of preheating temperature, interpass temperature and preheat mainteanance temperature
ISO 13918 Welding - Studs and ceramic ferrules for arc stud welding
ISO 13919-1 Welding - Electron and laser-beam welded joints - Guidance on quality level for imperfections - Part 1: Steel
ISO 13919-2 Welding - Electron and laser-beam welded joints - Guidance on quality level for imperfections - Part 2: Aluminium and its weldable alloys
ISO 13920 Welding - General tolerances for welded constructions - Dimensions for lengths and angles - Shape and position
ISO 14112 Gas welding equipment - Small kits for gas brazing and welding
ISO 14175 Welding consumables — Gases and gas mixtures for fusion welding and allied processes. Replaced EN 439:1994 in Europe.
ISO 14341 Welding consumables. Wire electrodes and deposits for gas shielded metal arc welding of non alloy and fine grain steels. Classification
ISO 14554 Resistance welding
ISO 14744 Electron beam welding, six parts
ISO 15607 Specification and qualification of welding procedures for metallic materials - General rules
ISO/TR 15608 Welding - Guidelines for a metallic material grouping system
ISO 15609 Specification and qualification of welding procedures for metallic materials - Welding procedure specification, five parts.
ISO 15610 Specification and qualification of welding procedures for metallic materials — Qualification based on tested welding consumables
ISO 15611 Specification and qualification of welding procedures for metallic materials — Qualification based on previous welding experience
ISO 15612 Specification and qualification of welding procedures for metallic materials — Qualification by adoption of a standard welding procedure
ISO 15613 Specification and qualification of welding procedures for metallic materials — Qualification based on pre-production welding test
ISO 15614 Specification and qualification of welding procedures for metallic materials - Welding procedure test, 13 parts.
ISO 15615 Gas welding equipment. Acetylene manifold systems for welding, cutting and allied processes. Safety requirements in high-pressure devices
ISO 15618-1 Qualification testing of welders for under-water welding. Diver-welders for hyperbaric wet welding
ISO 15618-2 Qualification testing of welders for under-water welding. Diver-welders and welding operators for hyperbaric dry welding
ISO 17635 Non-destructive testing of welds. General rules for metallic materials
ISO/TR 20172 Welding — Grouping systems for materials — European materials
ISO/TR 20173 Welding — Grouping systems for materials — American materials
ISO/TR 20174 Welding — Grouping systems for materials — Japanese materials
ISO 24394 Welding for aerospace applications. Qualification test for welders and welding operators. Fusion welding of metallic components
Saturday, February 15, 2014
Regulations for the Installation of Electrical Wiring, Electrical Equipment and Air Conditioning Equipment (Qatar General Electricity & Water Corporation "KAHRAMAA")
DOWNLOAD :
http://www.km.com.qa/sitecollectiondocuments/service%20regulations/en/regulationsfortheinstallationofelectricalwiringele.pdf
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