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Adjustable MCCB with Electronic Trip | 16A-1600A | Programmable Protection Curves

Reliable Adjustable MCCB Supplier

KRIPAL manufactures adjustable thermal magnetic MCCBs in the UKM1ADJ series, an enhanced version of the UKM1 MCCB with fully adjustable thermal and magnetic trip settings accessible from the front panel. The UKM1ADJ provides adjustable thermal overload protection from 0.7 to 1.0 times In and adjustable magnetic short-circuit protection from 5 to 10 times In, allowing the MCCB’s protection characteristics to be precisely matched to the circuit’s requirements after installation without replacing the trip unit. Available in frame sizes from 100AF to 630AF with breaking capacities up to 65kA at 400V AC, the UKM1ADJ uses the same accessories, mounting dimensions and busbar connections as the standard UKM1, making it a drop-in upgrade for switchboards where field-adjustable protection is required. The adjustable magnetic trip is particularly valuable in cascaded protection schemes, where the upstream MCCB’s instantaneous pickup must be set above the downstream device’s let-through current to achieve selective coordination. Certified to IEC 60947-2, the UKM1ADJ is specified for applications where the circuit’s protection requirements may change over the installation’s life or where precise coordination with other protection devices is critical.

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Adjustable MCCB with Electronic Trip | 16A-1600A | Programmable Protection Curves
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Understanding Electronic Trip MCCBs

An adjustable MCCB extends the standard thermal-magnetic protection with field-adjustable trip settings, giving the installation designer and commissioning engineer the flexibility to fine-tune the protection characteristics to the actual circuit conditions. The adjustable thermal setting allows the overload protection to be matched to the installed cable’s actual ampacity (which may differ from the design value due to cable grouping, ambient temperature or installation method), while the adjustable magnetic setting enables precise coordination with downstream devices to achieve selective fault clearing. This selection guide covers the adjustment ranges, coordination capabilities and applications where adjustable protection provides a clear advantage over fixed-setting MCCBs.

UKM1ADJ Adjustable MCCB Series Technical Specifications

Adjustable Thermal Overload Protection

The UKM1ADJ thermal trip is adjustable from 0.7 to 1.0 times In via a calibrated rotary dial, with the adjustment affecting the bimetallic strip’s deflection point relative to the trip latch. A 250A MCCB with the thermal setting at 0.8 In effectively becomes a 200A MCCB, protecting a circuit cable with 200A ampacity while using a standard 250A frame size. The thermal memory function (the bimetallic strip retains heat from a previous overload, reducing the trip time for a subsequent overload) is preserved at all adjustment settings. The adjustment dial is accessible from the front panel with the switchboard door open, and the setting is visible through a window on the MCCB front cover when the door is closed. A tamper-evident seal can be applied over the dial to prevent unauthorized field adjustment.

Adjustable Magnetic Instantaneous Protection

The UKM1ADJ magnetic trip is adjustable from 5 to 10 times In, allowing the instantaneous pickup to be raised above the downstream device’s short-circuit let-through current for selective coordination. For example, a 250A UKM1ADJ feeding a sub-distribution board with 63A MCBs: the MCB’s let-through current for a fault at the sub-board busbar may be 1500A (based on the MCB’s I squared t characteristic). Setting the upstream UKM1ADJ magnetic trip to 7 In (1750A) ensures that a sub-board fault clears the downstream MCB without tripping the upstream MCCB, maintaining power to other circuits fed from the same sub-board. The magnetic trip adjustment is independent of the thermal setting, and the instantaneous pickup is factory-calibrated at each of the five adjustment positions (5, 6, 7, 8, 10 In).

Selective Coordination with Downstream Devices

Selective coordination (also called discrimination) means that only the protective device closest to the fault operates, leaving upstream devices closed and maintaining power to healthy circuits. The adjustable magnetic trip is the primary tool for achieving this coordination in the instantaneous region. KRIPAL provides discrimination tables showing the maximum fault current at which the UKM1ADJ and a downstream MCB or MCCB remain selective, for each combination of upstream setting and downstream device rating. For a typical 250A UKM1ADJ with the magnetic trip set to 8 In (2000A) feeding a 63A C-curve MCB, selectivity is maintained up to 3.5kA, which covers the bolted fault current for a sub-distribution board located up to 50 meters from the main switchboard (limited by cable impedance).

Commissioning and Periodic Testing

The UKM1ADJ trip settings should be recorded during switchboard commissioning and verified by primary injection testing to confirm the MCCB trips at the set values. KRIPAL recommends a primary injection test set capable of injecting at least 120 percent of the set thermal trip current and 120 percent of the set magnetic trip current. The test results are recorded in the switchboard’s commissioning report and serve as the baseline for future periodic testing. The trip settings should be reviewed every 5 years as part of the installation’s periodic inspection per IEC 60364-6, and adjusted if the circuit’s load profile or the downstream protection configuration has changed. The adjustment dials include a locking mechanism that prevents drift from vibration, and the dial position is verified during the annual switchboard inspection.

Specify Adjustable MCCBs for Your Switchboard

  • Discrimination Study: Our engineers analyze your single-line diagram and provide UKM1ADJ settings with verified selectivity at every protection level.
  • Commissioning Support: We provide a primary injection test procedure and can witness the testing on site to verify the set points.
  • OEM Supply: Source UKM1ADJ MCCBs pre-set to your specified values and factory-tested, ready for switchboard integration.

Applications of Adjustable MCCBs

KRIPAL UKM1ADJ adjustable MCCBs provide the protection flexibility needed for installations where circuit loading changes over time, where downstream protection devices are upgraded, or where the initial protection design must be verified and fine-tuned during commissioning. The field-adjustable settings transform the MCCB from a factory-set device into a configurable protection element that adapts to the actual installation conditions.

Industrial Plant with Evolving Load Profile

A manufacturing plant’s sub-distribution board uses UKM1ADJ MCCBs on the feeder circuits because the production line configuration changes every 2-3 years as new machines are added or relocated. When a new 50 kW machine is added to a feeder that was originally designed for 100A, the UKM1ADJ thermal setting can be adjusted upward (within the cable’s ampacity limit) instead of replacing the MCCB. Conversely, if a machine is removed and the feeder cable’s ampacity is now oversized for the reduced load, the thermal setting is adjusted downward to provide closer overload protection for the remaining equipment. The adjustable magnetic trip ensures that selectivity with the new machine’s local MCBs is maintained after the load change.

Commercial Building Tenant Fit-Out Protection

A commercial office building’s floor distribution board uses UKM1ADJ MCCBs to feed each tenant’s sub-distribution board. Tenant fit-outs change the electrical load on each floor every 5-7 years as tenants move in and out, and the adjustable MCCB allows the building’s electrical contractor to adjust the feeder protection to match the new tenant’s maximum demand without replacing the MCCB. The adjustable magnetic trip is set to coordinate with the tenant’s own MCCB at their sub-board, which may be a different brand or rating depending on the tenant’s electrical contractor’s preference.

Generator Incomer with Seasonal Load Variation

A standby generator installation at a seasonal facility (agricultural processing plant, tourist resort) uses a UKM1ADJ MCCB on the generator incomer with the thermal setting adjusted seasonally. During the peak processing season when the facility operates at maximum load, the thermal setting is adjusted to 1.0 In to allow the generator to deliver its full rated output. During the off-season when only essential loads are running, the thermal setting is reduced to 0.8 In to provide closer overload protection for the reduced load and to prevent the generator from operating at low load (below 30 percent of rating) which causes wet stacking in diesel engines. The adjustment is recorded in the facility’s operating log and verified by the maintenance electrician during the seasonal changeover.

Temporary Construction Site Power Distribution

A construction site’s temporary distribution board uses UKM1ADJ MCCBs because the site electrical load changes daily as different trades work in different areas. When the structural steel erection crew moves to a new area, the electrician adjusts the relevant feeder MCCB’s thermal setting to match the welding machines’ connected load, then readjusts it when the finishing trades move in with lower-power tools. The adjustable magnetic trip ensures that the site’s larger motors (concrete pumps, tower cranes) do not trip the feeder MCCB on starting inrush while still providing adequate short-circuit protection. The trip settings are reviewed at the daily site electrical safety briefing and recorded in the site logbook.

Critical Infrastructure with Progressive Load Growth

A water treatment plant’s MCC uses UKM1ADJ MCCBs on the pump feeders because the plant’s treatment capacity is progressively expanded over a 10-year master plan. The MCCBs are initially installed at 160A frames with the thermal setting at 0.7 In (112A) for Phase 1, adjusted to 0.85 In (136A) for Phase 2 without replacing the MCCB, and eventually replaced with 250A frames for Phase 3 when the load exceeds 160A. The adjustable settings allow the plant operator to defer capital expenditure on larger MCCBs until genuinely needed, while maintaining adequate protection at every stage of the expansion.

Adapt Your Protection with Adjustable MCCBs

  • Protection Review: Our engineers review your installation’s present and future load profile and recommend UKM1ADJ settings for each stage.
  • Discrimination Verification: Request time-current coordination tables for your adjustable MCCB settings with all downstream devices.
  • OEM Supply: Source UKM1ADJ MCCBs pre-set to your initial settings, with adjustment instructions for future changes.
Applications of Adjustable MCCBs

KRIPAL Adjustable MCCB Manufacturing and Support

KRIPAL adjustable MCCBs with electronic trip units are manufactured on a combined production line where the molded case and contact mechanism from the standard MCCB platform are integrated with a microprocessor-based electronic trip unit. Each adjustable MCCB undergoes multi-parameter calibration and communication interface verification for global selective coordination and energy management applications.

Electronic Trip Unit Calibration Across Adjustable Protection Curves

The microprocessor trip unit is calibrated to verify accurate tripping at all adjustable set-points: long-time pickup (0.4 to 1.0 times In), long-time delay, short-time pickup (1.5 to 10 times Ir), short-time delay with I-squared-t ON/OFF, and instantaneous pickup (2 to 15 times In). Each setting combination point on the time-current curve is verified.

Communications Interface Assembly and Protocol Verification

MCCBs configured with Modbus RTU, Profibus, or other fieldbus communication modules are tested for correct data exchange: trip unit settings readback, real-time current measurement reporting, event logging of trip occurrences, and remote open/close command execution. Communication modules are functionally tested before integration.

LCD Display and HMI Assembly

The front-panel LCD display and navigation buttons are assembled and tested for correct display of all measurement screens (phase currents, ground fault current, power, energy) and settings menus. Display contrast and backlight are verified, and button tactile response is checked on every unit.

End-of-Line Multi-Point Trip Verification

Each adjustable MCCB undergoes a multi-point trip verification: long-time delay at 6 times Ir (verifying the selected time band), short-time delay at the selected pickup threshold, and instantaneous at 120 percent of the set value. Trip times at each verification point are compared against the published tolerance bands and recorded against the serial number.

Distributor Stock Holding Programs for Adjustable MCCBs

KRIPAL supports distributor inventory programs with agreed stock levels for standard adjustable MCCB models with commonly specified trip unit configurations. Technical support for trip unit setting coordination studies is included for volume distribution partners.

Private Label and OEM Branding for Adjustable MCCBs

Custom front-panel branding, OEM trip unit default settings, and project-specific documentation are available. Neutral-packaged supply is provided upon request for private label production.

Multi-Region Certification and Compliance Support

CE, UKCA, and IEC 60947-2 compliance documentation including EMC immunity certificates are provided. Type test reports with verified trip curves for all protection functions are available for panel builder compliance submissions.

Direct Technical Access to KRIPAL Trip Unit Engineers

Your technical team communicates directly with the engineers who designed the electronic trip unit firmware and calibration procedures. Application questions including selectivity studies and arc flash mitigation settings receive answers within 24 hours during China business hours.

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Frequently Asked Questions

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An adjustable moulded case circuit breaker is a circuit protection device that uses an electronic trip unit instead of a fixed thermal-magnetic mechanism. It protects electrical conductors and connected equipment against overload and short-circuit conditions, with the key advantage that all protection parameters including long-time pickup, long-time delay, short-time pickup, short-time delay, and instantaneous pickup can be adjusted in the field using rotary dials or digital interfaces. This adjustability allows one breaker model to serve multiple protection requirements, simplifies selective coordination with downstream devices, and enables protection settings to be modified as an installation's load profile changes over time without replacing the breaker.
KRIPAL adjustable MCCBs are available in frame sizes from 100A to 1600A with rated insulation voltage of 1000V and rated operational voltage of 690VAC. Short-circuit breaking capacity ranges from 35kA to 100kA at 415VAC depending on frame size and performance class. The electronic trip unit offers long-time pickup adjustable from 0.4 to 1.0 In, long-time delay adjustable per IEC 60947-2 curves, short-time pickup adjustable from 1.5 to 10 Ir, short-time delay adjustable from 0.05 to 0.4 seconds with I-squared-t selectable on/off, and instantaneous pickup adjustable from 2 to 12 In. Optional earth fault protection with adjustable sensitivity and delay is available. The trip unit is self-powered from internal current transformers, requiring no external auxiliary supply for protection functions. Operating temperature range is -5 to +70 degrees Celsius. Certifications include CE, CB Scheme, and IEC 60947-2 type test reports.
KRIPAL adjustable MCCBs are manufactured under ISO 9001 certified quality management. The product range carries CE marking and CB Scheme certification with IEC 60947-2 type test reports from KEMA and ASTA-recognised laboratories. Short-circuit breaking capacity has been verified at accredited independent test facilities for all frame sizes and voltage ratings. All products are RoHS compliant with REACH declarations maintained. For markets requiring national certification such as CCC for China, EAC for the Eurasian Customs Union, or specific Gulf Cooperation Council requirements, KRIPAL maintains certification documentation and can coordinate with local testing bodies. Full type test reports are provided to OEM partners and available to EPC contractors upon request.
Begin by determining the frame size based on the maximum continuous load current of the circuit, leaving headroom for future load growth. Select the breaking capacity class that exceeds the maximum prospective short-circuit current at the point of installation. Choose the trip unit configuration: standard LSIG protection covering long-time, short-time, instantaneous, and ground fault; LSI omitting ground fault for three-wire systems; or LS for applications where instantaneous protection is provided by a downstream device. Verify that the adjustable ranges for each protection function cover your coordination requirements. For energy management or BMS integration, specify the communication module option with Modbus RTU interface. Consider the installation environment: standard operating temperature range covers most indoor applications, but specify the extended temperature version for installations in unconditioned spaces or hot industrial environments. KRIPAL application engineers can review your single-line diagram, fault level calculations, and coordination requirements to recommend specific model numbers and initial settings.
Standard adjustable MCCB models in the most common frame sizes and current ratings are stocked at KRIPAL's Wenzhou warehouse with a lead time of 15 to 20 working days from confirmed purchase order. Non-standard configurations including specific communication options or extended temperature versions may require 25 to 35 working days. The minimum order quantity for standard models is 5 units per frame size. OEM partnership agreements can negotiate smaller minimums, scheduled deliveries, and consignment stock arrangements. Sample orders of 1 to 2 units for type testing or customer evaluation are available to qualified distributors. Shipping is arranged FOB Ningbo or Shanghai, with sea freight as the standard mode and air freight available for urgent requirements.
KRIPAL provides a 24-month warranty on adjustable MCCBs from date of shipment. Technical support includes application engineering for protection coordination, assistance with trip unit settings for complex installations, and troubleshooting of communication interfaces. KRIPAL supplies coordination study software to distributor partners that generates time-current curves for any combination of KRIPAL adjustable MCCBs and downstream protection devices, supporting the selectivity analysis required by many project specifications. For warranty claims, replacement breakers are shipped within 5 to 10 working days of confirmed defect depending on configuration. Spare trip units, terminal covers, and accessory kits are stocked for the full service life of each frame size. KRIPAL offers commissioning support for major projects, with engineers available to travel to site when arranged at time of order.

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