MCC motor control centers
- Configuration: low-voltage drawout switchgear assembly, one independent drawer unit per motor circuit
- Unit sizes: 8E / 16E / 24E / 32E (1E = 25 mm) standard-height units; feeder and control units can be mixed in the same section
- Circuit types: direct-on-line, reversing, star-delta, soft starter and VFD motor control units, plus feeder and bus-tie units
- Busbar: horizontal busbar ≤2000 A, vertical busbar selected by section rating; contact resistance and temperature rise tested on every unit
- Testing: mechanical operation, circuit resistance, insulation, dielectric and energized functional tests on every unit; records delivered with the cabinets
Specifications
The table below covers 80% of factory distribution room cases. Anything outside it we can still build — those are engineered items, quoted separately, with an indicative price the same day.
| Configuration | Low-voltage drawout switchgear assembly; frame is profile-assembled or welded construction |
|---|---|
| Standard sizes (W×D×H) | Width 600 / 800 / 1000 mm; depth 600 / 800 / 1000 mm; height 2200 mm, units in 8E increments |
| Unit sizes | 8E / 16E / 24E / 32E (1E = 25 mm); units of different heights can be mixed in the same cabinet |
| Enclosure construction | 2.0 mm cold-rolled carbon steel frame plus doors and side panels, electrostatic powder coated |
| Surface treatment | Degrease → derust → phosphating → electrostatic powder coating 60-80 μm, baked at 200 °C for 30 minutes |
| Drawer mechanism | Rack-in / rack-out mechanism with connected, test and disconnected positions and position indication |
| mechanical interlock | The door cannot be opened while a unit is in the connected position; the main circuit opens automatically before the drawer is withdrawn, preventing insertion or withdrawal under load |
| IP rating | IP41–IP54 (drawer unit panels IP40 or higher; select per operating environment) |
| Rated operating voltage | Main circuit AC 380V / 400V, 50 Hz; control circuit AC 220V or DC 24V |
|---|---|
| Horizontal busbar | ≤2000 A (larger ratings quoted per project), TMY tinned copper busbar |
| Vertical busbar | Configured per section rating, lapped to the horizontal busbar via dedicated connectors |
| Rated short-time withstand current | 50 kA / 65 kA (matched to system short-circuit capacity and main breaker, 1 s) |
| Unit type | Feeder unit, direct-on-line starter unit, reversing control unit, star-delta unit, soft starter / VFD unit |
| Unit rating | Motor control units typically up to 250 kW; feeder units use breakers selected per branch current |
| Primary contacts | Silver-plated contacts; insertion force and contact resistance tested unit by unit; secondary contacts for control and signal circuits |
| Protection and metering | Molded case circuit breaker + contactor + thermal overload relay (or electronic motor protection relay); optional multifunction power meter |
| Incoming + feeder section | Main incoming cabinet + multiple feeder units, supplying workshops or downstream distribution boxes |
|---|---|
| Motor control section | Multiple motor control units grouped together, configured as individual units by power rating and starting method |
| Bus tie sectionalizing scheme | Two busbar sections connected through a bus tie cabinet; supply is switched during maintenance or faults |
| Duty/standby pump set unit | Two control units set up in duty/standby logic, with automatic transfer and alarm output on fault |
| VFD unit scheme | VFD units are built as individual drawers or as fixed partitioned units with a dedicated cooling duct |
| Supervisory control scheme | Operating status and faults from each unit are collected via communication modules and uploaded to the central control room or energy management system |
| Assembly standard | GB/T 7251.1 / IEC 61439-1; withdrawable switchgear per GB/T 7251.12 / IEC 61439-2 |
|---|---|
| Clearance & creepage | Meets pollution degree 3 and overvoltage category III / IV requirements |
| Temperature rise | Busbar, joint contact and terminal temperature rise ≤70 K, recorded unit by unit |
| Short-time withstand | 50 kA / 65 kA · 1 s (matched to main breaker interrupting capacity) |
| Mechanical operation | Each drawer unit is operated through connect—test—disconnect positions 50+ times, with operating force and position feel recorded |
| Routine tests (every unit) | Circuit resistance, insulation resistance (≥1 MΩ), power frequency withstand voltage 2500V/1min, grounding continuity, and powered functional test |
| Documents with shipment | Electrical schematic, unit circuit schedule, BOM with brand and model, busbar temperature rise and contact resistance records, test report, factory photos |
Five steps to specify your run
A configuration summary is generated as you go. It travels with your inquiry, saving a round of confirmation.
Build details
Systems have been in service for decades, and the failure points are always the same few: poor busbar contact, water ingress at the door seal, high temperature rise in the correction cabinet, and mis-phased outgoing feeders. The six hard rules below are written for exactly these points — every cabinet can be traced to them.
Connected / test / disconnected positions of the drawer
Each drawer has three positions — connected, test and disconnected — with position indication. In the test position the control circuit can be energized to check logic without touching the main circuit; in the disconnected position the section is fully isolated. If the positions are not clearly defined, maintenance means shutting the section down.
Mechanical interlock to prevent misoperation
The door is locked while the unit is in the connected position, and the main circuit opens before the drawer can be pulled out. This interlock prevents misoperation — pull a drawer under load once and the contacts are ruined.
Every contact tested individually
The contact resistance of every primary contact is measured and recorded unit by unit. This is the item most often overlooked on drawer-type switchgear, and the most common cause of overheating and burnout on site.
Busbar temperature rise records
Temperature rise of busbars, joints and contacts is held to ≤70 K, recorded unit by unit and delivered with the cabinet.
Drawer operating force measured
Every drawer unit is cycled through connected–test–disconnected at least 50 times to confirm smooth operation and clear position feel.
Busbars designed by section
When unit count is high, busbars are designed by section, with a bus tie cabinet for sectional supply and maintenance transfer, so an outage on one section does not stop production on another.
Photos & enclosure construction
Below are photos taken in our own shop — from the complete unit down to the internal busbars and secondary wiring. Every build detail can be checked item by item.
Image key: 01–05 are shop photos (the numbers match the shot list). The line drawing shows the front elevation of the enclosure; dimensions match the specification table above.
Where these cabinets go
These are the routine applications — we can talk scheme and configuration directly. For the industry view, see the industry pages.
Factory floor power distribution and motor control
Dozens of motors on one production line controlled centrally, with maintenance that does not stop the whole section.
Water treatment and pumping stations
Centralized control and duty rotation for lift pumps, return pumps, blowers and other multiple circuits.
Mining and building materials production lines
Centralized motor control for crushers, screens, conveyors and dust collection equipment.
Metallurgy and chemical plants
Motor circuit control and sectional power supply for process units.
Logistics and warehouse sorting lines
Multi-circuit control and status monitoring for conveyors and sorters.
Electrical retrofit of older workshops
Converting scattered fixed-pattern control cabinets to drawer-type, improving maintenance efficiency.
Commercial terms
Specification dated September 2026; quotations follow this.
| Drawings & design | Free |
| MOQ | 1 unit (5 or more recommended for production) |
| Production lead time | 15-25 days after drawing approval |
| on-time delivery | 98% |
| Warranty | 12 months |
| Loading port | Ningbo / Shanghai, China |
| Component brands | Schneider / ABB / Siemens / Chint |
| Factory visit & dispatch confirmation | Factory visits welcome; finished-cabinet photos and video before dispatch |
| Capacity | 5,800+ units / year |
Documents for your engineering team
Selection manual, outline dimensions and RFQ checklist — for the customer's electrical engineer. All three documents are being organized by product line; download links go live once complete.
Six questions procurement and electrical engineers ask most
What is the difference between MCC and GGD?
GGD is fixed-pattern: simple construction, straightforward maintenance, lower cost. MCC is drawer-type: each motor circuit is a withdrawable unit, easy to service and quick to restore. For a small number of circuits with infrequent maintenance, GGD is more cost-effective; for many circuits, continuous production that cannot stop, and high maintenance requirements, use MCC.
How many circuits fit in one cabinet?
It depends on unit height and cabinet height. Taking a 2200 mm cabinet with about 72E (roughly 1800 mm) of usable height per cabinet: 8E units fit 9 in theory, 16E fits 4, 24E fits 3, and mixed configurations are laid out by actual combination. During design we run through the circuit schedule and tell you how many cabinets you need.
Can the primary contacts develop poor contact?
This is the critical component of drawer-type switchgear. We use silver-plated contacts, test insertion and withdrawal force and contact resistance on every unit, and run drawer operation tests to confirm all three positions engage correctly. In service, we also recommend periodic infrared temperature checks per your procedures, and prompt inspection if any temperature difference is abnormal.
Can the drawers be withdrawn while energized?
No. The mechanical interlock inside the cabinet breaks the main circuit before the drawer can be withdrawn. Live insertion or removal under load will arc and damage the contacts — that is exactly why the interlock is there. Do not bypass it.
Can VFDs also be built as drawers?
Yes, but VFDs generate significant heat and require parameter setup. Most projects build the VFD section as a fixed, compartmented unit with its own air duct, and use drawers for the remaining circuits. The final layout is set by the circuit schedule and heat dissipation requirements.
What do I need to provide for an inquiry?
Motor circuit schedule (power rating, starting method and control requirements for each motor), short-circuit capacity or transformer capacity, incoming and feeder requirements, cabinet mounting location and size limits. A system diagram is preferred; if you don't have one, we can still produce a preliminary design from the circuit schedule alone.
Other cabinet types in the same main circuit
Related products use color-block placeholders for now (product photos not yet complete; they will be replaced together). Internal links will be filled in once live URLs are confirmed.
Many circuits in the plant and you can't afford to shut down for maintenance?
Send us your motor circuit schedule and transformer capacity — free cabinet type and unit configuration layout · quotation within 24 hours. Direct from the source factory, MOQ 1 unit, 15–25 day delivery, 1-year warranty.
ISO 9001:2015 · CE(LVD+EMC) · CQC · IP65
When you write, include: single-line diagram or primary scheme, switch room layout, load list, and component brand requirements. You do not need complete drawings — capacity and cabinet type are enough to start.