Question 1

What IEC 61439 tests are mandatory for a motor control center (MCC) used in heavy manufacturing?

Accepted Answer

For MCCs in heavy manufacturing, mandatory type and routine tests per IEC 61439-1/-2 include dielectric (high-voltage) tests, temperature-rise verification on busbars and load-carrying parts, and verification of mechanical operation. Additionally, short-circuit performance (calculation and verification of short-time withstand and peak withstand currents—Icw, Ipk) must be demonstrated for the specified PSCC. Routine tests typically include insulation resistance measurement, mechanical operation, and functional checks of protection devices. Where internal arc protection is required, panels must pass internal arc tests (method referenced in IEC 61439 and IEC 61641) and be classified for an Internal Arc Classification (IAC). Coordination with IEC 60947 series (circuit-breaker making/breaking capacities) is used to ensure protective device compatibility.

Question 2

How do you size busbars and short-circuit ratings for 3,200 A PCC in a steel plant?

Accepted Answer

Sizing busbars for a 3,200 A PCC in a steel plant requires evaluating continuous current rating, temperature-rise limits (per IEC 61439), and prospective short-circuit current at the point of installation. Common practice is to select copper or aluminium busbars sized for thermal-rating at expected ambient temperatures (accounting for derating factors) and to verify short-time withstand (Icw) and peak withstand (Ipk) to match the PSCC—often 50–100 kA or higher in heavy industry. The busbar mechanical design must resist electrodynamic forces; therefore, busbar spacing, supports and bracing are calculated to withstand the peak forces defined by the PSCC. Coordination with upstream circuit breakers (IEC 60947-2) ensures selective isolation and device integrity.

Question 3

What forms of internal separation are recommended for manufacturing MCC lineups to enable safe maintenance?

Accepted Answer

Forms of internal separation commonly specified for manufacturing MCC lineups are Form 3b and Form 4b. Form 3b separates each functional unit (withdrawable or fixed cubicle) from the busbar and other units, enabling maintenance on individual units without exposing the busbar. Form 4b provides full segregation of all live parts into dedicated compartments (incoming, busbar, outgoing, and earth), which is ideal where live access must be avoided during maintenance. Both forms support safer replacement of starters or drives and reduce outage scope. The choice depends on required availability, footprint constraints, and whether withdrawable motor starters or VFD modules are used.

Question 4

How are VFD-heavy plants protected from harmonics and overheating within IEC 61439 panels?

Accepted Answer

Protection strategies include deploying tuned or active harmonic filters, detuned PFC banks, phase-shifting transformers, and VFD designs with multi-pulse topologies. Within IEC 61439 panels, thermal management is addressed by specifying adequate ventilation, forced cooling or air conditioning for enclosed drive rooms, and temperature-rise verification during type testing. Busbar and cable selection account for harmonic heating (skin and proximity effects). Protective coordination requires overcurrent devices sized for inrush and harmonic currents, and harmonic studies are typically performed during design to select filters or oversized passive components. Products like Schneider/Prisma drive centers often integrate space and thermal considerations for large VFD stacks.

Question 5

When are internal arc-rated (IAC) switchgear assemblies required in manufacturing facilities?

Accepted Answer

Internal arc-rated assemblies are required when the consequences of an internal arcing fault could endanger personnel or critical processes, or when local regulations and company safety policies mandate arc-resistant switchgear. Facilities with high PSCCs, limited separation between switchgear rows, or critical production lines (semiconductor fabs, steel mills, chemical plants) commonly require IAC designs. Tests per IEC 61439 and IEC 61641 validate the panel’s capability to withstand a specified arc energy and to provide defined protective measures (pressure relief, particulate containment, safe door openings). IAC classification and evidence from type tests should be included in FAT documentation.

Question 6

What enclosure and ingress protection levels should be specified for food and washdown manufacturing?

Accepted Answer

For food processing and washdown environments specify enclosures with high ingress protection—typically IP54 for indoor, dust-protected areas, IP55 for moderate washdown, and IP66 for heavy jet wash or outdoor exposure. Stainless-steel enclosures (AISI 304/316) are commonly used to resist corrosion and facilitate sanitation. Ensure gaskets, cable glands and ventilation filters are rated for the chosen IP level. IEC 61439 allows these environmental requirements to be integrated into the type testing and routine verification; thermal management and condensation control (heaters or controlled ventilation) should also be specified to prevent moisture-related failures.

Question 7

How is compliance with hazardous-area standards handled when panels serve explosive atmospheres?

Accepted Answer

When panels interface with hazardous areas, designers must comply with IEC 60079 series (explosion protection) in addition to IEC 61439 for assembly construction. Options include locating the main LV switchgear outside the hazardous zone and using Ex-rated motor starters, Ex d/ex e enclosures, or intrinsically safe control circuits inside the zone. Cable glands, pressurization, and purge systems must be certified to the appropriate IEC 60079 parts. Documentation must include ATEX/IECEx certificates for Ex components and a documented zoning assessment to justify panel placement and required protection concepts.

Question 8

What documentation and acceptance tests should EPCs request for IEC 61439 panels in a new plant?

Accepted Answer

EPCs should request full Type Test reports (or equivalent witnessed tests) demonstrating compliance with IEC 61439-1/-2/-3/-6, including dielectric tests, temperature-rise test data, short-circuit calculations and evidence, and internal arc test reports if applicable. Factory Acceptance Test (FAT) protocols with witness options, routine test records (insulation, mechanical operation, Park/functional checks), wiring diagrams, single-line schematics, cable schedules, protection coordination study, and product certificates (e.g., CE, ATEX/IECEx where relevant) should be supplied. FATs should include functional verification of PLC/SCADA communications (Modbus/Profibus/EtherNet/IP), protective relay settings, and VFD/drive commissioning procedures.

Industrial Manufacturing

Panel Solutions for Industrial Manufacturing

Recommended Component Brands

Frequently Asked Questions

Request a Quote