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...

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...

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...

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,...

Friday, August 10, 2012

Control Circuits

Control Circuits Control  Control components are used in a wide variety of applications with varying degrees of complexity. One example of a simple control circuit is a circuit that turns a light on and off. In this circuit, the control component is often a single-pole switch.  ...

Tuesday, August 7, 2012

Thursday, August 2, 2012

Pollution Degree

The level of pollution in the environment in which the Assembly is intended to be installed. Four categories are defined in the Standard as follows:   Pollution degree 1 : No pollution or only dry, non-conductive pollution occurs. Pollution degree 2 : Normally, only non-conductive pollution occurs. Occasionally, however, a temporary                             ...

Wednesday, August 1, 2012

ROUTINE TESTS

These tests have a totally different function to Type Tests, BS EN 60439-1, states:   ‘Routine tests are intended to detect faults in materials and workmanship. They are carried out on every ASSEMBLY after its assembly or on each transport unit. Another routine test at the place of installation is not required.’   Hence, Routine Tests on Assemblies are normally undertaken...

Tuesday, July 31, 2012

PARTIALLY TYPE TESTED ASSEMBLY (PTTA)

IEC 60439-1, defines a PTTA as: ‘A low-voltage switchgear and controlgear assembly, containing both type-tested and nontype- tested arrangements provided the latter are derived (e.g. by calculation) from type tested arrangements which have complied with the relevant tests’.   This means: • The assembly will be derived from a Type Tested Assembly. • Deviations...