This page contains a Flash digital edition of a book.
Feature Industry standards ‘The new standard IEC 61439 is applicable to: LV power

distribution switchgear; motor control centres; control panels – lighting, PLC, industrial application, etc; metering panels; wall mounted enclosures; sub distribution boards; busbar trunking systems and assemblies for construction sites’

Verification of temperature rises is time consuming and expensive

Verification and testing

There are 13 design characteristics and 21 single verifications specified by the IEC 61439 that need to be verified by testing and comparison with a reference design and assessment. All of the relevant verifications that enables Ri4Power modular switchgear to meet the IEC 61439-2 standard have been carried out at the international well known IPH test laboratory and the company’s own accredited test laboratories. A full range of verification tests can also be found with Rittal Power Engineering Software. Tests

on individual

devices to their respective product standards are not an alternative to the design verification in this standard for the assembly. Verification of rise

ture (part the standard)

• Derivation of the rated values of similar variants

• Calculation methods Verification using the calculation method is confined to low voltage controlgear assemblies up to 630A and 1600A. For higher current ratings, derivation and testing verification must be performed. It is a requirement to record all heat rise data and the method of verification used. Heat rise calculation and the effect of heat on the assembly is critical to the performance of components such as circuit breakers, fuses and controlgear. For example, moulded case circuit breakers are compliant

to IEC 60947 which tests the circuit breaker in free air. The performance of the circuit breaker is then recorded. Under IEC 61439 the circuit breaker is tested within an assembly as the maximum rated performance can deviate from the nominal rating because the environment has changed for the circuit breaker. Higher ambient conditions will apply due to environmental conditions such as: the protection category (IP rating), size of functional unit (size of the enclosure where the circuit breaker is fitted), or assem- blies with forced ventilation, etc.

For verification of temperature rise, the actual achievable rated current and the rated diversity factor of the respective circuit should be indicated for both the manufacturer and the user. Merely stating the rated currents of the switchgear or individual components of the assembly is not sufficient, since this may not make allowance for environmental influences as previously stated. Rittal has undertaken temperature rise testing with

tempera- 10.10

of is the most

time-consuming verification and can be expensive, regardless of which method is used. For verification of temperature rise the options available are: • Testing

the leading manufacturers of circuit breakers in various functional unit sizes and recorded all test data. Results have been published within Rittal’s Ri4Power systems’ catalogue and show the de-rated current rating of the circuit breaker. This figure should be used by the design engineer when specifying circuit breakers. Another feature of the new standard is the naming of Inc as the rated current of the circuit (operating current of the load and not the rating of the circuit breaker as listed under IEC 60947, free air testing). The standard IEC 61439 divides responsibility for the

manufacture of a low voltage switchgear assembly between the original manufacturer and the assembly manufacturer.

> 10



Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28