Heat Dissipation Installation requirements

 

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LEGRAND POWER GUIDE

Measurement of the insulation resistance

- the insulation resistance must be measured with amegohmmeter (external or with standalone source) at

a minimum voltage of 500 VDC

- the assembly being tested must be turned off and there must be no receiver devices connected

- all the breaking devices must be in position i (on)

- the voltage is applied between each circuit and the exposed conductive part

- it is possible to link all the poles: phases and neutral,except in tnC layout in which the pen conductor is considered to be linked to the exposed conductive part

of the assembly.Devices (measurement windings, instruments) which would not withstand the test voltage must have their supply terminals short-circuited.

the measurement conditions can influence the results obtained. measurements should not be carried out temperatures below dewpoint (condensation will

dampen the surfaces).

the insulation resistance decreases with the temperature.if repeated measurements have to be taken,the environmental conditions must be recorded. the period for which the voltage is applied also has a major influence, and measurement can be considered to consist of three sequences. at the start of measurement, the device charges the capacitor which represents the installation in relation to earth and the leakage current is at its highest.

 

LEGRAND POWER GUIDE

Enclosure resistance to damp

This test, carried out in accordance with standard

ieC 60068-2-3, checks that the insulation characteristics

of the enclosure, busbars and conductor supports

are not affected after 4 hours' exposure in a steam

chest (40°C at 95% relative humidity).

the insulation used has a tracking current resistance

of at least 400 V, which means it is not very sensitive to

damp (group i and group ii according to ieC 60664-1).

Sheet Metal Powder Coating Process

  

>> What is Powder Coating?

Powder coating is a commonly used surface finishing technique. It is a type of coating that is applied as a free-flowing, dry powder.

The powder coating process involves applying a finely ground resin (powder) to a substrate and subjecting this powder to heat. During the heating process, the powder melts and creates a uniform, continuous coating.

The final cured powder coating is the same as a 2-pack wet paint. The main difference between a powder coating and conventional wet paint is that the powder coating does not require a solvent to keep the binder and filler parts in a liquid suspension form.

>> Two Types of Powder Coating

There are two types of powder available on the market.

1. Thermoplastic powder:

A thermoplastic powder coating is one that melts and flows with the application of heat, but maintains the same chemical composition when it solidified on cooling. Thermoplastic powders will remelt when heated.

Thermoplastic powders do not chemically react during application or curing, nor do they cross-link. Therefore, they can be reheated, enabling an entire coating to be reflowed. This is a useful property allowing minor flaws to be touched-up.

2. Thermosetting powders:

Most powder-coating materials are thermosetting powders. Thermosetting powders will not remelt when heated. The thermosetting powders incorporate a cross-linker into the formulation. When the powder is baked, it reacts with other chemical groups in the powder polymer and increases the molecular weight and improves the performance properties.

The solid resins melt and flow chemically, and cross-link within themselves or with other reactive components forming a higher molecular-weight reaction product. The coating film formed by this reaction is heat stable and will not soften back to a liquid on further exposure to heat.

The types of resins commonly used in thermosetting powder include:

·         several types of epoxies

·         hydroxyl and carboxyl types of polyesters

·         several types of acrylics

·         several types of silicones

 

>> Brands of Powder Coat

Several brands of powder coat are available including Morton, Tiger Drylac, Spraylat, HB Fuller, Cardinal, O'brien, etc.

>> The Benefits of Powder Coating

Powder coating materials are shipped ready to use and are easy to apply, thus labor costs associated with training, setup, and processing are low when compared with liquid coating processes.

Although equipment and materials costs are similar in powder coating and liquid coating processes, powder coating process provides a number of advantages over other surface coating methods.

·         Powder coatings provide excellent corrosion, impact, and abrasion resistance

·         Powder coatings emit no or extremely low volatile organic compounds

·         powder coatings produce much fewer rejects

·         Powder coatings produce much less hazardous waste than liquid coatings

·         Less floor space are required with powder coating line

·         Powder coatings produce much thicker coatings without running or sagging

·         Powder coatings have more uniform finishes

·         A wide variety of special effects can be achieved with powder coatings which would be very hard or impossible to make with liquid coating process

 

>> Applications of Powder Coating

Manufacturers use powder coating processes in a wide variety of applications as they are versatile and present savings in labor, materials, and energy cost. Powder coats are also very durable.

Powder coatings are now used in hundreds of applications. One of the biggest powder-coating users is the appliance industry. The high-quality finish is both attractive and durable, and a viable alternative for porcelain enamel and liquid finishes on traditional appliance surfaces.

The automotive industry represents approximately an additional 15% of the North American powder coating market. Wheels, bumpers, roof racks, door handles, interior panels, and various "under-the-hood" parts are being powder coated.

The architectural and building market uses powder coating on file cabinets, shelving, aluminum extrusions for window frames, door frames, and modular office furniture.

>> The Powder Coating Process

Electrostatic spraying is the most widely used method of applying powder-coating materials. This process is the most efficient and effective means of applying powder coatings.

Five basic pieces of equipment are needed for the electrostatic-spray process.

1. Powder feeder unit
2. Electrostatic powder applicator
3. Control module for powder applicator
4. Powder spray booth
5. Powder recovery unit

The powder coating process involves three basic steps:

1. Part preparation or part pre-treatment
2. Powder application
3. Powder Curing

> Part Preparation or part pre-treatment process:

The part must be cleaned of oil, soil, lubrication greases, metal oxides, welding scales, etc before it can be powder coated. A variety of chemical and mechanical methods are used to do the cleaning job. The selection of the method depends on the size and material of the part to be powder coated, or the type of soil to be removed and the performance requirement of the finished product.

Chemical pre-treatment involves the use of phosphates or chromates in a submersion or spray application. These often occur in multiple stages and consist of degreasing, etching, de-smutting, various rinses and the final phosphating or chromating of the substrate. The pre-treatment both cleans and improves bonding of the powder to the metal.

> Powder Application Process

The most common way of applying the powder coating to metal objects is to spray the powder using an electrostatic gun. The gun imparts a positive electric charge on the powder, which is then sprayed towards the grounded object by mechanical or compressed air spraying and then accelerated toward the workpiece by the powerful electrostatic charge.

> Powder Curing Process

When a thermoset powder is exposed to elevated temperature, it begins to melt, flows out, and then chemically reacts to form higher molecular weight polymer in a network-like structure. This cure process requires a certain degree of temperature for a certain length of time in order to reach full cure and establish the full film properties for which the material was designed. Normally the powders cure at 200°C (390°F) in 10 minutes.

Copyrights by : OEM Enclosure Inc. © 2011

http://www.oemenclosure.com/powder-coating.php

Parts of IEC 61439 series

Parts of IEC 61439 series

 

IEC 61439-1 General rules

 

IEC 61439-2 Power switchgear and control gear ASSEMBLIES

(Replacing IEC 60439-1)

 

IEC 61439-3 Distribution boards (to supersede IEC 60439-3)

 

IEC 61439-4 ASSEMBLIES for construction sites

(to supersede IEC 60439-4)

 

IEC 61439-5 ASSEMBLIES for power distribution

(to supersede IEC 60439-5)

 

IEC 61439-6 Busbar trunking systems

(to supersede IEC 60439-2)

The salt spray test

The salt spray test is a standardized test method used to check corrosion resistance of coated samples. Coatings provide corrosion resistance to metallic parts made of steel, zamak or brass. Since coatings can provide a high corrosion resistance through the intended life of the part in use, it is necessary to check corrosion resistance by other means. Salt spray test is an accelerated corrosion test that produces a corrosive attack to the coated samples in order to predict its suitability in use as a protective finish. The appearance of corrosion products (oxides) is evaluated after a period of time. Test duration depends on the corrosion resistance of the coating; the more corrosion resistant the coating is, the longer the period in testing without showing signs of corrosion.

Salt spray testing is popular because it is cheap, quick, well standardized and reasonably repeatable. There is, however, only a weak correlation between the duration in salt spray test and the expected life of a coating (especially on hot dip galvanized steel where drying cycles are important for durability), since corrosion is a very complicated process and can be influenced by many external factors. Nevertheless, salt spray test is widely used in the industrial sector for the evaluation of corrosion resistance of finished surfaces or parts.

 

Testing equipment

 

The apparatus for testing consists of a closed testing chamber, where a salted solution (mainly, a solution of 5%sodium chloride) is atomized by means of a nozzle. This produces a corrosive environment of dense saline fog in the chamber so that parts exposed in it are subjected to severely corrosive conditions. Typical volumes of these chambers are of 15 cubic feet (420 L) because of the smallest volume accepted by International Standards on Salt Spray Tests - ASTM-B-117, ISO 9227 (400 litres) and now discontinued DIN 50021 (400 litres). It has been found very difficult to attain constancy of corrosivity in different exposure regions within the test chambers, for sizes below 400 litres. Chambers are available from sizes as small as 9.3 cu ft (260 L) up to 2,058 cubic feet (58,300 L). Most common machines range from 15 to 160 cubic feet (420–4,500 L).[1][2][3]

Tests performed with a standardized 5% solution of NaCl are known as NSS (neutral salt spray). Results are represented generally as testing hours in NSS without appearance of corrosion products (e.g. 720 h in NSS according to ISO 9227). Other solutions are acetic acid (ASS test)

and acetic acid with copper chloride (CASS test), each one chosen for the evaluation of decorative coatings, such as electroplated copper-nickel-chromium, electroplated copper-nickel or anodized aluminium.

 

Uses

 

Typical coatings that can be evaluated with this method are:

Phosphated surfaces (with subsequent paint/primer/lacquer/rust preventive)

Zinc and zinc-alloy plating (see also electroplating). See ISO 4042 for guidance

Electroplated chromium, nickel, copper, tin

Coatings not applied electrolytically, such as zinc flake coatings according to ISO 10683

Organic coatings

Hot-dip galvanized surfaces are not generally tested in a salt spray test (see ISO 1461 or ISO 10684). Hot-dip galvanizing produces zinc carbonates when exposed to a natural environment, thus protecting the coating metal and reducing the corrosion rate. The zinc carbonates are not produced when a hot-dip galvanized specimen is exposed to a salt spray fog, therefore this testing method does not give an accurate measurement of corrosion protection. ISO 9223 gives the guidelines for proper measurement of corrosion resistance for hot-dip galvanized specimens.

Painted surfaces with an underlying hot-dip galvanized coating can be tested according to this method. See ISO 12944-6.

Testing periods range from a few hours (e.g. 8 or 24 hours of phosphated steel) to more than a month (e.g. 720 hours of zinc-nickel coatings, 1000 hours of certain zinc flake coatings).

 

Wikipedia

Check list of checks to be made during the final quality inspection (How to assemble a switchboard guide)

Compliance checks

>>Identification & column numbers

>>Type

>>Dimensions

>>Compliance of front panel, block diagram

>>Handling devices

Visual checks

>>Paint (colour, homogeneity, finishing)

>>No scratches and deformations

Frame, structure

>>Functioning of doors, swivelling front panels

>>Locks (type, functioning)

>>IP degree of protection

Switchgear

>>Position

>>Fastening

>>Characteristics: nominal range, breaking capacity

>>Identification and marking

>>Safety perimeter

>>Mechanical operation

>>Mechanical indication (test position, connected, etc.)

>>Plugging-in and withdrawing procedure

>>Striker pin

>>Accessibility of switchgear

>>Ability to connect on terminals or pads

>>Accessibility for connection

>>Locking, foolproofing

Busbars

>>Busbar cross-section

>>Coating and internal arc device

>>Busbar support (fastening device and number)

>>Marking

>>Compliance of joint blocks

Cables & flexible bars

>>Cross-section and characteristics of conductors

>>Compliance of installation mode (fastening, sharp edges, etc.)

>>Auxiliary Power separation

>>EMC protection

Connection

>>Compliance and quality of bolted connections

(e.g. covering and fastener type)

>>Torque and marking

>>Crimping quality

Protection of persons

>>Earth bar (cross-section and fastening)

>>Earthing braids

>>Forms

>>Bonding continuity

>>IP of measuring devices (fastened on doors)

>>Blanking shutters

>>Terminal guards and covers

>>Fastening of protective barriers

Safety distances

>>Clearance

>>Creepage distances

Dielectric check (power circuit)

 

Insulation check (power circuit)

>>Megohmmeter

Electrical compliance

>>Phase order >>Phasing test

>>Voltages, control polarities >>Electric tests, voltmeter

>>Distribution of polarities (inter-column connections) >>Electric tests, voltmeter

Functional tests: >>Test consoles, injection test bench, etc.

>>Operating sequence (controls and signalling)

>>Checking of source transfer

>>Electrical and mechanical inter-locking

>>Checking of opening/closing orders of units

>>Trip tests (defects)

>>Information report (OF-SDE-SD)

>>Signalling (indicator lights, etc.)

>>Injection on protection and measurements (values, etc.)

Measurement and protection:

>>Protection tests (fault tripping, etc.)

>>Injection on measuring devices (Pa, PWH, etc.)

>>CT winding direction

Device settings (circuit monitors, protections, etc.)

Automation and communication:

>>Equipment addressing

>>Network tests (read/write)

>>Verification of PLC inputs/outputs

>>Validation of the PLC (according to functional specifications)

Cleaning and preparation of columns

Documentation related to switchboard

>>Switchboard building drawings

>>Installation and maintenance documents

>>Switchgear guides

>>List of shortages

Packaging

>>Compliance of the package

>>Compliance of packaging

 

Schneider electric (How to assemble a switchboard guide)

Electrical codes

Electrical codes are sets of rules established by governing bodies which state:

 

• Type of equipment to be used in a given situation

• Appropriate use

• Installation procedures,

including how and where it should be installed

Codes usually carry mandatory compliance, and can apply nationally or to a

more limited area, such as a single local municipality. In any case, such codes can

be used to facilitate the successful installation of equipment, or stop it dead in its

tracks. Codes are powerful, and there must be a keen awareness of the various

codes and their applications.

One of the best known set of codes is the NEC (National Electrical Code), which

works in conjunction with UL requirements. The NEC is a set of electrical installation

standards published by the National Fire Protection Agency (NFPA). The

NEC is the most widely adopted electrical code in the United States and regulates

all electrical equipment used in power distribution systems, from the source to private

residences, and even to the configuration of the circuits within homes.

As you learn about different types of electrical equipment, you will become very

aware of the standards and codes that are most relevant to that particular type of

equipment. For now, just be aware of their existence and importance.

Here is a list of the most common standards and codes (but it is far from all-inclusive):

 

• ANSI (American National Standards Institute)

• BSI (British Standards Association)

• CE Mark (Certified European Mark)

• CEC (Canadian Electric Code)

• CSA (Canadian Standards Association)

• IEC (International Electrotechnical Commission)

• IEEE (Institute of Electrical and Electronic Engineers)

• ISO (International Standards Organization)

• NEC (National Electrical Code)

• NEMA (National Electrical Manufacturers Association)

• UL (Underwriters Laboratories, Inc.)

 

EATON

The new IEC 61439: better or worse than its predecessor 60439?

Improvements in IEC 61439 series compared to IEC 60439 series.

The new document structure:

Readability of the IEC 61439 has been improved compared to the IEC 60439 by implementing the

new structure of the clauses:

a) Clauses for normative reference and definitions are separated;

b) Newly introduced in clause 4 is a table with all the typical units for LV systems;

c) Also n important change is the separation the constructional requirements (clause 8) and the

performance (electrical) requirements (clause 9);

d) Design verification in clause 10 has been detailed, with more guidance and rules for the

various verification methods;

e) Routine verification in clause 11 has been separated from the design verification.

These improvements acknowledge that the assembly manufacturer/designer focuses on the

constructional and performance requirements and less bothers with de design verification which is for

the laboratories to address.

 

Introduction of designated design verification methods

A significant change in the new LV Assembly standard is the introduction of three methods of design

verification to replace TTA and PTTA (Type Tested Assembly and Partially Type Tested Assembly).

Where TTA in principle required complete testing of all assemblies or modular LV assembly systems,

the new standard acknowledges that assemblies or modular LV assembly systems may be

manufactured in various similar arrangements that can be sorted in variants. IEC 61439 requires

design verification of the critical variants only. To sort the critical variants a number of rules are

provided in order to avoid superfluous testing.

Where PTTA allowed calculation (that was applied to the discretion of the assembly manufacturer) for

some verifications the new standard introduces concrete rules for this method. In essence these rules

limit the loading of parts and conductors to values that are considered safe in case no true test is

performed. Note that verification of temperature rise is limited to assemblies with a total current of

1600 A, above that one is obliged to test with current.

The new standard allows the manufacturer to combine the different methods for verification as long as

it is indicated in the test report which method was used for the individual design verification.

Better or worse?

In general the new standard is better, due to the new structure, the new introduced clear methods of

verification and abandoning the vague terms TTA and PTTA.

It is worse where it bothers laboratories to verify the constructional requirements regarding the

incorporation of switching devices and components, wiring and terminals, information that is not

always easy to come by. Probably only half of the verifications in this area are useful. Many of the

items are subject to an agreement between user and manufacturer and therefore may vary for each

one-off assembly.

 

Written for Eaton MCC Forum

Bas Bouman

Applications and Standards LV Systems

Eaton Electric B.V.

Hengelo The Netherlands.

12 May 2010

Insulation resistance testing