Friday, June 28, 2013
Saturday, June 22, 2013
NEMA Ratings and IP Equivalency Chart
NEMA Rating | IP Equivalent | NEMA Definition | IP Definition | |
1 | IP10 | Enclosures constructed for indoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment and to provide a degree of protection against falling dirt | 1 = Protected against solid foreign objects of 50mm in diameter and greater | 0 = Not Protected |
2 | IP11 | Enclosures constructed for indoor used to provide a degree of protection to personnel against incidental contact with the enclosed equipment, to provide a degree of protection against falling dirt, and to provide a degree of protection against dripping and light splashing of liquids | 1 = Protected against solid foreign objects of 50mm in diameter and greater | 1 = Protected against vertically falling water drops |
3 | IP54 | Enclosures constructed for either indoor or outdoor used to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to proved a degree of protection against falling dirt, rain, sleet, snow, and windblown dust; and that will undamaged by external formation of ice on the enclosure | 5 = Protected against dust - Limited to ingress (no harmful deposit) | 4 = Protected against water sprayed from all directions - Limited to ingress permitted. |
3R | IP14 | Enclosures constructed for either indoor or outdoor used to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt, rain, sleet, and snow; and that will be undamaged by external formation of ice on the enclosure | 1 = Protected against vertically falling water drops | 4 = Protected against water sprayed from all directions - Limited to ingress permitted. |
3S | IP54 | Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt, rain, sleet, snow, and windblown dust; and in which the external mechanism(s) remain operable when ice laden. | 5 = Protected against dust - Limited to ingress (no harmful deposit) | 4 = Protected against water sprayed from all directions - Limited to ingress permitted. |
4 | IP66 | Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt, rain, sleet, snow, windblown dust, splashing water, and hose-directed water; and that will be undamaged by the external formation of ice on the enclosure | 5 = Protected against dust - Limited to ingress (no harmful deposit) | 6 = Protected against strong jets of water from all directions - Limited to ingress permitted. |
4X | IP66 | Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt, rain, sleet, snow, windblown dust, splashing water, hose-directed water, and corrosion; and that will be undamaged by thee external formation of ice on the enclosure | 5 = Protected against dust - Limited to ingress (no harmful deposit) | 6 = Protected against strong jets of water from all directions - Limited to ingress permitted. |
5 | IP52 | Enclosures constructed for indoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt; against settling airborne dust, lint, fibers, and flyings; and to provide a degree of protection against dripping and light splashing of liquids. | 5 = Protected against dust - Limited to ingress (no harmful deposit) | 2 = Protected against direct sprays of water up to 15° from the vertical. |
6 | IP67 | Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt; against hose-directed water and the entry of water during occasional temporary submersion at a limited depth; and that will be undamaged by the external formation of ice on the enclosure. | 6 = Totally protected against dust | 7 = Protected against the effects of temporary immersion between 15cm and 1m. Duration of test 30 minutes. |
6P | IP67 | Enclosures constructed for either indoor or outdoor use to provide a degree of protection to the personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt; against hose-directed water and the entry of water during prolonged submersion at a limited depth; and that will be undamaged by the external formation of ice on the enclosure | 6 = Totally protected against dust | 7 = Protected against the effects of temporary immersion between 15cm and 1m. Duration of test 30 minutes. |
12 and 12K | IP52 | Enclosures constructed (without knockouts) for indoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt; against circulating dust, lint, fibers, and flying; and against dripping and light splashing of liquids | 5 = Protected against dust - Limited to ingress (no harmful deposit) | 2 = Protected against direct sprays of water up to 15° from the vertical. |
13 | IP54 | Enclosures constructed for indoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt; against circulating dust, lint, fibers, and flyings; and against the spraying, splashing, and seepage of water, oil, and noncorrosive coolants. | 5 = Protected against dust - Limited to ingress (no harmful deposit) | 4 = Protected against water sprayed from all directions - Limited to ingress permitted. |
IP Codes in accordance with IEC 529 & UL
There are several different uses of IP Codes, as described in IEC 529. IP Codes can have the following arrangement:
· First character only, such as IP 3X
· Second character only, such as IP X4
· Both characters, such as IP 34
The first character indicates the degree of protection against the ingress of solid foreign objects. First character definitions are as follows:
0 - Non-protected
1 - Protected against solid foreign objects of 50 mm diameter and greater
2 - Protected against solid foreign objects of 12.5 mm diameter and greater
3 - Protected against solid foreign objects of 2.5 mm diameter and greater
4 - Protected against solid foreign objects of 1.0 mm diameter and greater
5 - Dust-protected
6 - Dust-tight
The second character of the IP Code indicates the degree of protection against the ingress of water with harmful effects. Second-character definitions are as follows:
0 - Non-protected
1 - Protected against vertically falling water drops
2 - Protected against vertically falling water drops as the enclosure is tilted 15 degrees
3 - Protected against spraying water
4 - Protected against splashing water
5 - Protected against water jetting
6 - Protected against powerful water jetting
7 - Protected against temporary immersion
8 - Protected against continuous immersion
UL sample requirements
Some UL testing chambers are limited in size. Please note that these size restrictions apply only for the tests specified below. If your sample will not fit into the test chambers, a smaller prototype may be used as long as the same type of hinges, gaskets, and other mechanisms are used at the same pressures.
· IP 5X/6X -- Sample must fit into dust chamber measuring 3-1/2 ft. wide by 3 ft. tall by 7 ft. long. The door to the chamber measures 2 ft. by 3-1/2 ft.
· IP X7/X8 -- Sample must fit into container measuring 23 in. diameter by 6 ft. deep.
UL 508 - The UL Safety Standard for Industrial Control Equipment
Industrial Control Equipment is a term commonly used to represent discrete components ranging from selector switches, relays, contactors, motor starters, timers, pilot lights, to complex system of these components. It encompasses more than 30 different product categories and 100 different devices (See Figure1). |
Figure 1: Examples of industrial control devices covered by UL 508 | |
Industrial Control Devices | Examples |
Motor starters and controllers | Including manual, magnetic, and solid-state starters and controllers |
Overload relays | Including thermal, magnetic, and solid-state overload relays |
Control circuit switches and relays | Including pushbutton stations, selector switches, time-delay relays and pilot lights |
Switches | Including float, flow, pressure, vacuum-operated, mercury-tube and proximity switches |
Autotransformers, resistors and rheostats | Variable voltage and motor starting |
Programmable controllers | Including numerical control systems and industrial microprocessor/computer systems |
Industrial Control Equipment is used extensively in industrial applications including starting, stopping, regulating, controlling, reversing, changing speed, or protecting electric motors. Components for motor control are installed primarily in control panels, motor control centers, industrial machines as well as energy distribution assemblies. Industrial Control Equipment is required to be designed, built and evaluated for their function and safety in compliance with an established National / International standard. UL 508, covers the safety requirements for Industrial Control Equipment. |
Wednesday, January 2, 2013
Motor protection
Overload relay with reclosing lockout
They should always be used where
continuous contact devices (two-wire
control) are concerned (e.g. pressure and
position switches), to prevent automatic
restarting. The reset button can be fitted as
an external feature in order to make it
accessible to all personnel. Overload
relays for example are always supplied
with manual reset. but can be converted to
automatic reset by the user.
Overload relays without reclosing
lockout
They can be used only with pulsed contact
devices (three-wire control) such as
pushbuttons etc., because on these, the
cooling of the bimetal strips cannot lead to
automatic reconnection.
Special circuitry
Special circuitry such as is found in
star-delta switches, individually
compensated motors, current
transformer-operated overload relays etc.
may require that the relay settings deviates
from the motor rated operational current.
Frequently recurring operating cycles
It makes motor protection difficult. The
relay should be set to higher than rated
motor current in view of its shorter time
constant. Motors which are rated for a high
operating frequency will stand this setting
to a certain degree. Although this will not
ensure complete protection against
overload, it will nevertheless provide
adequate protection against non-starting.
Back-up fuses and instantaneous
releases
They are needed to protect not only the
motor, but also the relay, against the
effects of short-circuits. Their maximum
rating is shown clearly on every relay and
must be adhered to without fail. Higher
ratings – chosen for instance according to
the cable cross-section – would lead to the
destruction of the motor and relay.
The following important questions and
answers give a further guide to the
behaviour of an installation with motor
protection.
To what current must the overload relay
properly be set?
To the rated motor current – no higher, no
lower. A relay set to too low a figure will
prevent the full utilization of the motor; set
too high, it will not guarantee full overload
protection. If a correctly set relay trips too
frequently, then either the load on the
motor should be reduced or the motor
should be exchanged for a larger one.
When is it right for the overload relay to
trip?
Only when the current consumption of the
motor increases due to mechanical
overloading of the motor, undervoltage or
phase failure when the motor is under full
load or thereabout, or when the motor fails
to start due to a stalled rotor.
When does the overload relay fail to trip
in good time although the motor is
endangered?
With changes in the motor which do not
cause an increase in current consumption:
Effects of humidity, reduced cooling due to
a reduction in speed or motor dirt,
temporary additional external heating of
the motor or bearing wear.
What causes destruction of the overload
relay?
Destruction will take place only in the
event of a short-circuit on the load side of
the relay when the back-up fuse is rated
too high. In most cases, this will also
endanger the contactor and motor.
Therefore, always adhere to the maximum
fuse rating specified on every relay.
3-pole overload relays should be so
connected in the case of single-phase and
DC motors so that all three poles of the
overload relay carry the current, whether
in 1-pole or 2-pole circuits.
An important characteristic feature of
overload relays conforming to IEC/EN
60947-4-1 are the tripping classes (CLASS
10 A, 10, 20, 30). They determine different
tripping characteristics for the various
starting conditions of motors (normal
starting to heavy starting duty).
EATON
Monday, December 31, 2012
Friday, December 21, 2012
Motor starters
Star-delta starter
This is the most popular and commonly
used starting method for motor ratings
> 4 kW (400 V).
• Electronic motor starter (EMS) and soft
starter
These enable the soft and low-noise
starting of the motor. This eliminates
interference producing current peaks
and jerks during switching. The startup
and deceleration phase of the motor can
also be time-controlled depending on the
load.
• Frequency inverter
This enables time-controlled motor
starting, motor braking and operation
with infinitely variable motor speeds.
Depending on the application, different
types of frequency inverters are used:
– with the voltage/frequency control
(U/f) or vector control for
frequency-controlled motor operation,
– with vector control or servo control for
high speed accuracy and additional
torque adjustment.
Associated circuit diagrams
Direct on line starter
Direct-on-line starter
In the simplest case the motor is
connected directly with a contactor. The
combination of motor protection and
cable protection (fuse) is called a motor
starter (MSC = Motor Starter
Combination).
By applying the full mains voltage to the
motor windings, DOL starting may
produce large starting currents which
may result in troublesome voltage
changes. Direct-on-line starting
three-phase motors must not cause
interference voltage changes in the
public utility grid. This requirement is
generally fulfilled if the apparent power
of a three-phase asynchronous motor
does not exceed 5.2 kVA or its startup
current does not exceed 60 A.
With a mains voltage of 400 V and 8 times
the starting current, this corresponds to
a rated motor current of around 7.5 A and
thus a motor rating of 4 kW.
The motor rating denotes the mechanical
output of the motor at the shaft.
Thursday, December 20, 2012
Wednesday, December 12, 2012
Standards
CE
The CE conformity marking shall indicate conformity to all the obligations imposed
on the manufacturer, as regards his products, by virtue of the European
Community directives providing for the affixing of the CE marking.
When the CE marking is affixed on a product, it represents a declaration of the
manufacturer or of his authorized representative that the product in question
conforms to all the applicable provisions including the conformity assessment
procedures. This prevents the Member States from limiting the marketing and
putting into service of products bearing the CE marking, unless this measure
is justified by the proved non-conformity of the product.
Flow diagram for the conformity assessment procedures established by the Directive
2006/95/CE on electrical equipment designed for use within particular voltage range:
Manufacturer
Technical file
The manufacturer
draw up the technical
documentation
covering the design,
manufacture and
operation of the
product
EC declaration of
conformity
The manufacturer
guarantees and declares
that his products are in
conformity to the technical
documentation and to the
directive requirements
Naval type approval
The environmental conditions which characterize the use of circuit breakers for
on-board installations can be different from the service conditions in standard
industrial environments; as a matter of fact, marine applications can require
installation under particular conditions, such as:
- environments characterized by high temperature and humidity, including saltmist
atmosphere (damp-heat, salt-mist environment);
- on board environments (engine room) where the apparatus operate in the
presence of vibrations characterized by considerable amplitude and duration.
In order to ensure the proper function in such environments, the shipping registers
require that the apparatus has to be tested according to specific type
approval tests, the most significant of which are vibration, dynamic inclination,
humidity and dry-heat tests.
Standards
“Low Voltage” Directive 2006/95/CE
The Low Voltage Directive refers to any electrical equipment designed for use
at a rated voltage from 50 to 1000 V for alternating current and from 75 to
1500 V for direct current.
In particular, it is applicable to any apparatus used for production, conversion,
transmission, distribution and use of electrical power, such as machines,
transformers, devices, measuring instruments, protection devices and wiring
materials.
The following categories are outside the scope of this Directive:
• electrical equipment for use in an explosive atmosphere;
• electrical equipment for radiology and medical purposes;
• electrical parts for goods and passenger lifts;
• electrical energy meters;
• plugs and socket outlets for domestic use;
• electric fence controllers;
• radio-electrical interference;
• specialized electrical equipment, for use on ships, aircraft or railways, which
complies with the safety provisions drawn up by international bodies in which
the Member States participate.
Directive EMC 2004/108/CE (“Electromagnetic Compatibility”)
The Directive on electromagnetic compatibility regards all the electrical and electronic
apparatus as well as systems and installations containing electrical and/
or electronic components. In particular, the apparatus covered by this Directive
are divided into the following categories according to their characteristics:
• domestic radio and TV receivers;
• industrial manufacturing equipment;
• mobile radio equipment;
• mobile radio and commercial radio telephone equipment;
• medical and scientific apparatus;
• information technology equipment (ITE);
• domestic appliances and household electronic equipment;
• aeronautical and marine radio apparatus;
• educational electronic equipment;
• telecommunications networks and apparatus;
• radio and television broadcast transmitters;
• lights and fluorescent lamps.
The apparatus shall be so constructed that:
a) the electromagnetic disturbance it generates does not exceed a level allowing
radio and telecommunications equipment and other apparatus to operate
as intended;
b) the apparatus has an adequate level of intrinsic immunity to electromagnetic
disturbance to enable it to operate as intended.
An apparatus is declared in conformity to the provisions at points a) and b) when
the apparatus complies with the harmonized standards relevant to its product
family or, in case there aren’t any, with the general standards.
ABB MCC