Name: Rittal Motor Control Center (MCC)
Brand: Rittal

Question 1

What rated currents and short-circuit ratings can a Rittal Ri4Power-based MCC achieve?

Accepted Answer

Ri4Power systems integrated into Rittal VX25/TS 8 MCCs are typically type-tested up to 5500 A continuous busbar ratings; engineered solutions can extend to 6300 A with appropriate busbar cross-sections and jointing. Short-circuit withstand (Icw) depends on busbar design and jointing; common configurations achieve 50–100 kA for 1 s. These values must be verified by type and design verification tests per IEC 61439-2 (short-circuit verification) and coordinated with IEC 60947 equipment ratings. Final Icw is determined during project-specific calculations and factory or site testing.

Question 2

Which forms of internal separation are available in a Rittal MCC—and what do Form 3b and 4b mean?

Accepted Answer

Rittal MCCs can be configured for Forms of Separation from Form 2 up to Form 4b; the common MCC offerings use Form 3b–4b. Form 3b provides segregation between busbar, functional units and cable compartments (separate busbar chamber plus separate functional unit enclosures), while Form 4b adds individual enclosure of each functional unit inside the cubicle (highest segregation for serviceability and fault limitation). These definitions and verification requirements are specified in IEC 61439-1 Clause 6 and IEC 61439-2 for LV switchgear assemblies.

Question 3

Can Rittal MCCs integrate VFDs and what thermal/EMC measures are required?

Accepted Answer

Yes. VX25/TS 8 MCCs with Ri4Power support integration of VFDs from major drive vendors. Best practice includes segregated cable ducts for power/control, EMC filtering, screened motor cables, and dedicated cooling (TopTherm fans, Blue e+ coolers) to manage drive losses. EMC-compliant transient protection and input chokes are mounted per IEC 61000-series guidance. Drive ventilation, additional IP protection for electronics, and spacing for heat dissipation are validated during the IEC 61439 temperature-rise verification.

Question 4

Is Ri4Power a type-tested system and how does that affect verification under IEC 61439?

Accepted Answer

Ri4Power is offered as a type-tested busbar and distribution solution; type-tests (short-circuit, temperature-rise, dielectric) reduce the scope of project-specific design verification required by IEC 61439-2. Using a documented type-tested system simplifies compliance evidence for rated current and short-circuit withstand, but project-specific configuration checks (e.g., functional unit arrangement, cable entries, changes in aperture) still require verification or routine testing per IEC 61439-1.

Question 5

How do withdrawable/plug-in functional units work in Rittal MCCs and what safety interlocks are used?

Accepted Answer

Withdrawable units use positive draw-out mechanisms with defined service positions (connected/test/isolated) and built-in mechanical interlocks that prevent live access. Typical designs include earthing and shorting blades, auxiliary contact feedback, and handle interlocks compliant with IEC 60947-1/-5. Rittal provides standardized frames and mounting adaptors to ensure repeatable alignment, quick replacement, and safe isolation for maintenance while maintaining required separation forms under IEC 61439.

Question 6

Can a Rittal MCC be specified for hazardous areas (Ex) or offshore use?

Accepted Answer

Yes. While standard Ri4Power/VX25 enclosures are for non-hazardous installations, Rittal offers adaptations and third‑party certified solutions for hazardous areas in accordance with IEC 60079. Options include pressurized/purged enclosures, encapsulated Ex e/tb modules, and IP-enhanced enclosures for corrosive/offshore atmospheres. Project-specific certification and selection of Ex-rated components (motors, starters, VFDs) are required and typically coordinated during the design phase.

Question 7

Which communication protocols and motor protection relays are commonly integrated in Rittal MCCs?

Accepted Answer

Rittal MCCs integrate motor protection relays and communication modules from Siemens, Schneider, ABB, Eaton, and others. Common protocols include Modbus RTU/TCP, Profinet, EtherNet/IP and, for larger motor/generator protection, IEC 61850. Motor protection devices (electronic overloads, protection relays, intelligent starters) are mounted in withdrawable units and wired to the Ri4Power distribution backbone for centralized monitoring and SCADA integration.

Question 8

What verification and testing does an engineer require for Rittal MCCs under IEC 61439?

Accepted Answer

Per IEC 61439-1/-2 the project requires documented type and design verification (or reliance on Ri4Power type‑test reports), routine tests (dielectric, continuity, functional checks), temperature-rise testing or calculation, and short-circuit verification. If internal arc protection is needed, tests per IEC 61641 apply. Factory FATs should include insulation resistance, functional unit interlocks, verification of IP rating, and witnessable short-circuit or simulation reports to satisfy EPC and end‑user commissioning requirements.

Rated Current (InA)	Up to 6300A
Short-Circuit Rating (Icw)	50–100kA / 1s
Rated Voltage	690V AC
Functional Units	Withdrawable / Fixed
Form of Separation	Form 3b–4b
IP Protection	IP31–IP54
IEC Standard	IEC 61439-2
Component Brand	Rittal

Rittal Motor Control Center (MCC)

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