The Harmonisation of Product Standards for Frequency Inverters and Programmable Logic Controllers
Dirk R.F. Müller speaks to ElectroAutomation magazine
Today’s global products need to be manufactured with multiple regional standards in mind. As a result, many manufacturers opt to produce different product lines for North America and the ‘IEC market’. The harmonisation of industrial automation equipment standards significantly reduces the overall number of requirements, as well as the associated costs. When all necessary certification testing is supplied by a single partner – like UL – manufacturers also benefit from faster time to market.
Most industrial automation products have traditionally needed to comply with a great variety of standards depending on their target markets, whether they lie in North America, Europe or Asia. Since 2002, IEC member countries have applied the new standard for frequency inverters IEC/EN 61800-5-1 (Adjustable speed electrical power drive systems – Part 5-1: Safety requirements – electrical, thermal and energy). North America, on the other hand, requires the application of UL508C (Power Conversion Equipment” and CAN/CSA-C22.2 No. 274 “Adjustable Speed Drives ). IEC/EN 61131-2 has been the applicable standard for the safety of control equipment, such as programmable logic controllers (PLC), while the U.S. market follows UL508 (Industrial Control Equipment) and Canada CAN/CSA-C22.2 No. 142 (Process Control Equipment).
Whereas UL and Canada Standards Association (CSA) standards are, for the most part, equivalent in terms of their technical requirements, there are major differences between these and the corresponding IEC/EN standards. The differences mainly apply to clearance and creepage distances, protection type and the classification of loads, e.g. HP rating vs. AC-3 or pilot duty rating vs. AC-1.
Moving towards harmonisation
The idea that advantages can be gained through the harmonisation of standards is hardly new. Over 10 years ago for the industrial area, UL presented its first efforts to harmonise the North American and IEC standards for contactors and motor starters (UL/IEC 60947-4-1). UL experts have since become established members of many IEC standards committees.
The second major harmonisation project involved frequency inverters, resulting in the converged standard UL/IEC 61800-5-1 (Adjustable Speed Electrical Power Drive Systems – Part 5-1: Safety Requirements – Electrical, Thermal and Energy).
In a third harmonisation project, the requirements of North America and the IEC changed simultaneously. The requirements for electrical safety were extracted from IEC 61131-2 (Programmable controllers – Part 2: Equipment requirements and tests) and transferred into the new IEC 61010-2-201 (Safety requirements for electrical equipment for measurement, control, and laboratory use – Part 2-201: Particular requirements for control equipment). This transfer was one step towards the expansion of a new IEC 61010 range of standards with a focus on factory automation. At the same time, a harmonised clause UL 61010-2-201 was created – an industry first, as it means there are no national differences for the USA.
The new UL 61010-2-201 was published in January 2014 and is applicable in combination with UL 61010-1. This standard will replace UL 508 in January 2016 for all new certifications of PLC and other controllers. UL 508 certifications carried out in the past will remain unaffected. Manufacturers will face significant changes when building new PLCs and controllers according to these new requirements. The main differences between UL 508 and UL 61010-2-201 involve the IEC-based concept of clearance and creepage distances, as well as expanded testing in the area of internal component faults and routine production reviews. The standard CAN/CSA C22.2 No. 61010-2-201 (published April 2014) applies for Canada. This standard also does not contain any national differences to IEC 61010-2-201. As a result, manufacturers can choose a single testing procedure that covers all the requirements of UL, CAN-CSA and IEC/EN. For manufacturers, this translates to substantial savings in both time and money.
The new UL 61800-5-1 was published in June 2012. Starting in February 2016, all new frequency inverters will have to be certified according to UL 61800-5-1 for the U.S. market. UL 508C certifications carried out in the past remain unaffected. Though manufacturers of frequency converters do still need to take some U.S. differences into account, the new UL 61800-5-1 will allow for combined testing to cover both UL and IEC requirements.
With the current edition of UL 61800-5-1, there are many small national differences between the UL and IEC standards. However, UL 61800-5-1 is predominately based on the IEC standard, such as in the area of clearance and creepage distance requirements. As regards the component fault inspection requirements of UL 61800-5-1, the new standard is much more detailed than both UL 508C and IEC 61800-5-1. For typical frequency inverters, short circuits at the inverter output are quickly registered, and the power is shut off via semiconductor switch in most constructions. This practically eliminates the chance of any greater damage. As opposed to UL 508C, UL/IEC 61800-5-1 requires short-circuit tests at the inverter outputs, as well as at all power outputs, such as DC intermediate circuits or brake resistor connections. Depending on the construction, this can have a significant impact and often leads to blown fuses.
If there is an internal fault, e.g. due to component failure in the DC circuit, it can result in an internal short circuit with substantial consequences. This short circuit is initiated from several sources. For one, it results from the internal condensers in the DC intermediate circuit and, for another, from the supply-side mains rectifier. In another case – depending on the type of power circuit – the short circuit power of the supply system acts as a parameter. For this reason, the UL 61800-5-1 tests on internal component faults are carried out under the same conditions as the short circuit test.
The CB Scheme – a passport to world markets
The CB scheme is a global initiative for the mutual recognition of tests by many important markets. As a result, UL can offer a single testing programme to help manufacturers access the national certification marks of over 50 countries. Manufacturers will benefit from having a single contact for complete Global Market Access, greatly simplifying product launches in the most important markets. After years of experience with the CB Scheme, UL has issued more CB certificates than any other certification company.
Like a passport, a CB certificate provides direct access to many countries. Nevertheless, some countries have additional national regulations that, following the same analogy, could be compared to a country-specific visa. Products must meet these additional requirements to enter those markets.
These national requirements can vary greatly from country to country and may change frequently. With a global network and subsidiaries in over 40 countries, UL is at home in every market and can thus provide manufacturers with effective support for all aspects of market access. UL offers tailored services for accessing all the necessary product approvals, with special expertise in regions such as Europe, India, China, Argentina and the Middle East. Particularly in the area of frequency inverters and PLC, a CB certificate often results in easy multi-market access.
Contact us to obtain standards expertise early in the design process
It is important to contact UL and identify target markets at an early stage in the product development process. Doing so makes it possible for the approval process to take consideration of national differences and requirements such as voltage, network type or the language of warnings. In order for national certification marks to be issued on the basis of a CB certificate, all national differences must be included and additional rules followed. These can include, for example, that no SMT process is used for China or that, in Brazil, tests must be carried out in an ILAC-accredited laboratory.
The harmonisation of North American and IEC-based standards greatly eases the process for manufacturers that wish to access global markets, particularly manufacturers of frequency inverters and controls. The vision of covering many important markets with a single testing programme is becoming a reality and will substantially reduce the costs and time needed for international product launches.
Dirk R.F. Müller
Manager, Principle Engineers at UL
Member of several standards working groups at UL, IEC and DKE.
Technical Assessor in the IECEE CB Scheme and member of the ETF7 working group for certification decisions relating to automation products.
20 years of experience in the area of testing power and automation components.
Offizielle CB-Statistik März 2014 – IECEE-CMC/1441/INF