Durable Motor Protection Circuit Breaker Manufacturer

CDADA is a professional manufacturer of Motor Protection Circuit Breakers, boasting a 52,400 m² production facility and comprehensive production lines. With 20 years of experience in the manufacturing and sales of these products, we offer advanced and durable solutions that can be customized to meet specific operational requirements.

What Is a Motor Protection Circuit Breaker?

A Motor Protection Circuit Breaker (MPCB), also known as a motor circuit breaker or manual motor starter, is a specialized electromechanical protection device designed specifically for safeguarding electric motors against operational faults. Unlike general-purpose MCCBs, MPCBs integrate overload protection, short-circuit protection, and manual switching in a single compact unit, optimized for the unique demands of motor starting and running conditions.

Operating under IEC 60947-4-1 (contactors and motor-starters) and IEC 60947-2 (circuit-breakers), MPCBs handle current ratings from 0.63A to 100A (extending to 150A in specialized ranges), with adjustable thermal settings to match specific motor full-load currents. They are designed to withstand motor inrush currents (typically 6-8× full-load current during startup) without nuisance tripping, while providing precise protection against sustained overloads and phase failures.

The defining advantage of MPCBs lies in their motor-optimized trip characteristics—thermal elements calibrated for motor heating curves and magnetic trips set well above starting current but below damaging fault levels. This eliminates the need for separate contactors and overload relays in many applications, reducing panel space and installation complexity.

MPCB Product Categories & Configurations

Classification	Type	Current Range	Key Characteristics
Frame Size	Compact (NS2-25 series)	0.63A – 25A	DIN rail mounting, 100kA Icu at 400V, screw/spring terminals
	Standard (NS2-32 series)	0.1A – 32A	Extended range, thermal-magnetic trip, phase-failure protection
	Power (NS2-80/100 series)	10A – 100A	Higher thermal capacity, 15-50kA Icu, panel mount
Trip Technology	Thermal-Magnetic	0.63A – 100A	Bimetallic overload + solenoid short-circuit, adjustable Ir
Trip Technology	Electronic	25A – 150A	Microprocessor-based, phase imbalance, ground fault, communication
Control Type	Push Button	0.63A – 32A	Red OFF button, direct motor control, local operation
	Rotary Handle	10A – 100A	Lockable in OFF position, padlock attachment (3 locks)
	Remote Control Ready	25A – 100A	Shunt trip/undervoltage release compatibility
Utilisation Category	AC-3	All ratings	Squirrel-cage motor starting/stopping during running
Utilisation Category	AC-4	0.63A – 32A	Squirrel-cage motor starting, plugging, inching (10×In)
Pole Configuration	3-Pole	0.63A – 100A	Standard three-phase motor protection
Pole Configuration	4-Pole	0.63A – 32A	Three-phase + neutral or two-speed motor switching

Current Setting Range Examples:

NS2-25E: 0.63-1A, instantaneous trip 13A (13×In)

NS2-25F: 1-1.6A, instantaneous trip 22.5A (14×In)

NS2-25G: 1.6-2.5A, instantaneous trip 33.5A (13.4×In)

NS2-25H: 2.5-4A, instantaneous trip 51A (12.75×In)

NS2-25J: 6-10A, instantaneous trip 138A (13.8×In)

NS2-25L: 13-18A, instantaneous trip 223A (12.4×In)

NS2-80B: 40-63A, instantaneous trip 756A (12×In)

Core Functions & Protection Capabilities

Integrated Motor Protection Functions

Function	Detection Principle	Technical Parameters
Overload Protection (Thermal)	Bimetallic strip heat expansion	Adjustable 0.63-100A, tripping class 10A (2-10s at 6×In), ambient compensation -20°C to +60°C
Short-Circuit Protection (Magnetic)	Electromagnetic solenoid plunger	Fixed 12-14×In (motor-optimized), <20ms operation, 100kA breaking capacity
Phase Failure Protection	Differential heating of bimetals	Trip within 10s at 0.9×In with single phase open, prevents single-phasing damage
Phase Imbalance Protection	Thermal differential between phases	Trip when current unbalance >30% for >2 minutes
Locked Rotor Protection	Sustained high current (>6×In for >2s)	Integrated with thermal curve, prevents rotor/stator damage
Manual Switching	Mechanical toggle/push button	100,000 electrical operations, ON-OFF motor control, isolation function

Trip Characteristics & Coordination

MPCBs feature inverse-time thermal curves specifically matched to motor heating characteristics:

Thermal Trip Times (Typical Class 10A):

1.05×Ir: No trip (2h)

1.2×Ir: Trip 10-20 minutes

1.5×Ir: Trip 2-4 minutes

6×Ir: Trip 2-10 seconds (starting current withstand)

12-14×Ir: Instantaneous magnetic trip (<20ms)

Magnetic Trip Settings:

Set 20-30% above motor locked-rotor current

Prevents nuisance trips during startup (6-8×FLC for 1-3 seconds)

Ensures rapid clearance of short-circuit faults

Application Environments & Use Cases

Industry Sector	Specific Application	Typical Specifications
Industrial Automation	Conveyor systems, pumps, compressors, fans	4A-25A, AC-3, 100kA Icu, push button control, DIN rail
HVAC Systems	Chillers, air handling units, cooling towers	10A-32A, ambient compensation, high starting frequency
Water & Wastewater	Submersible pumps, booster stations, irrigation	6A-40A, dry-run protection (pressure switch integration), IP65 enclosures
Machine Tools	Lathes, milling machines, grinders	1.6A-10A, high inrush withstand, frequent starting (AC-4)
Material Handling	Cranes, hoists, conveyors, elevators	10A-63A, rotary handle, lockable OFF, mechanical interlocking
Food & Beverage	Mixers, grinders, packaging machines	2.5A-16A, stainless steel accessories, washdown duty
Renewable Energy	Solar tracking motors, wind turbine auxiliaries	1A-10A, extended temperature range (-25°C to +70°C)
Oil & Gas	Drilling rig auxiliaries, pump jacks	25A-100A, tropicalized (T2), corrosion-resistant, high shock resistance

Manufacturing Process & Production Workflow

Precision Manufacturing Sequence

Raw Material IQC → Bimetallic Element Production → Electromagnetic Coil Winding → Contact System Fabrication → Arc Chute Assembly → Mechanism Integration → Calibration & Testing → Final Assembly → Quality Verification → Packaging

Critical Manufacturing Stages

Stage	Process Details	Quality Control Points
Bimetallic Element Production	Inconel/passivated steel composite rolling, heat treatment for deflection characteristics, stamping to shape, calibration marking	Deflection rate 0.15-0.25mm/°C, trip temperature ±3% tolerance, stability testing 1000h at 200°C
Electromagnetic Coil Manufacturing	Copper wire winding (0.3-0.8mm), vacuum varnish impregnation, magnetic core assembly	DC resistance ±5%, dielectric strength 2kV/1min, pickup/dropout voltage testing
Thermal Trip Calibration	Automated calibration station with precision current injection, temperature chamber (-20°C to +60°C)	Trip time at 1.05×Ir, 1.25×Ir, 6×Ir recorded, ±10% tolerance, permanent marking
Magnetic Trip Setting	Solenoid air gap adjustment, spring pre-load calibration, sealed after setting	Instantaneous trip at 12-14×Ir ±10%, <20ms operation, tamper-proof sealing
Contact System Assembly	Silver-alloy (AgNi or AgCdO) contacts brazed to copper carriers, wiping action geometry	Contact resistance <1mΩ, hardness HV 100-150, brazing strength >50MPa
Arc Chute Integration	Ceramic splitter plates (6-12 plates), arc runner alignment, deionizing chamber assembly	Dielectric strength >2.5kV, arc quenching <10ms at 400V, dimensional ±0.1mm
Final Mechanism Assembly	Toggle/push button mechanism, trip-free override, contact pressure springs, handle linkage	Mechanical endurance 100,000 operations, contact pressure 5-10N, bounce time <3ms
Comprehensive Testing	Primary injection testing (0.5-1000A), time-current curve verification, phase failure simulation	100% automated testing, data logging, QR code traceability

Primary Raw Materials & Component Specifications

Component	Material Specification	Supplier Standards	Key Properties
Bimetallic Strip	Inconel 718/passivated steel composite (ASTM TM2) or brass/steel	ASTM B388, IEC 60404	Deflection rate 0.2mm/°C, stability ±3% over 20 years, creep resistance
Electromagnetic Coil	Enameled copper wire Class F (155°C) or Class H (180°C)	IEC 60317, NEMA MW 35	Breakdown voltage >2kV, solderability 390°C/2s, flexibility
Magnetic Core	Silicon steel laminations (0.35-0.5mm) or solid iron	IEC 60404-8, JIS C 2552	High permeability, low remanence, consistent pickup characteristics
Main Contacts	Electrolytic copper (Cu-ETP) + AgNi 90/10 or AgCdO tips	ASTM B152, IEC 60368	Conductivity ≥100% IACS, arc erosion resistance, anti-welding
Contact Springs	Beryllium copper (CuBe2) or stainless steel 301	ASTM B196	Fatigue life >100,000 cycles, consistent pressure 5-10N
Arc Chute Plates	Steatite ceramic or alumina (Al₂O₃ 95%)	IEC 60672	Heat resistance >1000°C, dielectric strength >15kV/mm
Arc Runners	Copper-tungsten (CuW) or steel with copper plating	ASTM B702	Arc erosion resistance, magnetic arc deflection
Moulded Case	BMC (DMC-2) thermosetting plastic or PA66 GF30	IEC 60664-1, UL 94 V-0	Tracking index >600V, heat resistance 180°C, impact >7 kJ/m²
Operating Mechanism	Zinc-plated steel or stainless steel 304	ISO 898-1, ASTM A240	Tensile strength >400MPa, corrosion resistance, wear-resistant
Terminals	Brass C36000 or copper C11000 with tin plating (5-8μm)	ASTM B16/B187	Current density 1.0-1.5 A/mm², torque withstand 1.5-3.0Nm

Standards Compliance & Testing Protocols

International Standards Framework

Standard	Scope	Applicable Ratings
IEC 60947-2	Low-voltage switchgear - Circuit-breakers	Short-circuit protection, breaking capacity, isolation
IEC 60947-4-1	Contactors and motor starters - Electromechanical contactors and motor starters	Motor starting, overload protection, coordination with contactors
EN 60947-2 / EN 60947-4-1	European harmonized versions	CE marking, EU market compliance
GB/T 14048.2 / GB/T 14048.4	Chinese national standards	CCC certification, China market

Mandatory Type Tests (IEC 60947-4-1 & IEC 60947-2)

Test Category	Specific Test	Acceptance Criteria
Temperature Rise	Continuous current at rated Ir	Terminals ≤80K (silver), ≤65K (bare), bimetal ≤85K
Dielectric Properties	Power-frequency withstand (2kV-2.5kV/1min), impulse (6kV-8kV)	No breakdown, no flashover
Overload Protection	1.05×Ir (no trip 2h), 1.25×Ir (trip ≤2h), 1.5×Ir (trip <4min)	Conventional tripping times per tripping class
Short-Circuit Breaking	Icu (ultimate), Ics (service) at rated voltage	100kA @ 400V (compact), 15-50kA @ 400V (power range)
Coordination	Type 1 or Type 2 with SCPD	Type 2: no damage, immediate reoperation
Phase Failure Sensitivity	Single-phase operation at 0.9×Ir	Trip within 10s, prevents motor single-phasing
Mechanical Endurance	100,000 no-load operations	<5% parameter drift, no mechanical failure
Electrical Endurance	100,000 AC-3 operations (0.63-32A)	Contact wear <50%, trip characteristics maintained
Environmental	Damp heat (IEC 60068-2-30), cold, dry heat	Functional after conditioning, no corrosion
EMC	Immunity to radiated/conducted interference (electronic types)	No nuisance tripping, EN 60947-4-1 Annex L

Factory Quality Control & Inspection Standards

Incoming Material QC (IQC)

Material	Inspection Items	Sampling Plan	Equipment
Bimetallic strips	Deflection rate, resistance, stability, dimensional tolerance	Per batch, sample testing	Thermal oven, deflection gauge, resistance bridge
Enameled wire	Diameter, insulation thickness, breakdown voltage, flexibility	AQL 0.65	Micrometer, dielectric tester, elongation tester
Silver contact tips	Purity, density, hardness, brazing alloy compatibility	Per batch	Spectrometer, hardness tester, metallurgical microscope
Plastic compounds	Glass content, viscosity, cure characteristics, flammability	Per batch	Melt flow indexer, DSC, UL 94 test apparatus
Steel components	Hardness, tensile strength, dimensional tolerance	AQL 1.0	Rockwell hardness tester, tensile machine, CMM

In-Process Quality Control (IPQC)

Station	Control Parameters	Frequency	Method
Bimetal calibration	Trip temperature, deflection at reference temp, marking	Every unit	Automated calibration station with current injection
Coil winding	Turns count, tension, resistance, insulation	Every unit	Automated winding machine with feedback, ohmmeter
Magnetic trip setting	Air gap, spring pre-load, instantaneous trip current	Every unit	Primary injection tester (50-1000A), timing measurement
Contact assembly	Contact gap, pressure, alignment, resistance	Every 100 units	Force gauge, micro-ohmmeter, optical comparator
Mechanism integration	Toggle force, trip-free function, handle operation	Every unit	Automated functional tester, force-displacement curve

Final Quality Control (FQC) & Outgoing QC (OQC)

Test Item	Standard	Sample Size
Thermal trip verification	1.05×Ir (no trip), 1.25×Ir (trip), time recording	100%
Magnetic trip verification	12-14×Ir instantaneous trip, <20ms	100%
Phase failure test	Single-phase operation, trip within 10s	100%
Dielectric withstand voltage	2kV AC/1min	100%
Insulation resistance	>100MΩ @ 500V DC	100%
Contact resistance	<1mΩ per pole	100%
Mechanical operation	10 ON-OFF cycles, smooth operation	100%
Visual & dimensional inspection	Zero defects on critical dimensions	100%
Marking permanence	Solvent wiping, abrasion test	AQL 1.0
Packaging integrity	Drop test, vibration (ISTA 3A)	Per lot

Production Infrastructure & Manufacturing Capability

Advanced Production Equipment

Equipment Category	Machine Specification	Function	Capacity
Bimetal Production Line	Precision rolling mill, heat treatment furnace, stamping press	Bimetallic strip manufacturing, calibration	50,000 strips/day
Automated Calibration	6-station rotary calibration system with temperature chambers	Thermal trip calibration (-20°C to +60°C)	2,000 units/day
Primary Injection Testing	1000A primary current injection set	Time-current curve verification	500 units/hour
Coil Winding	CNC winding machines with tension control	Electromagnetic coil production	10,000 coils/day
Contact Brazing	Controlled atmosphere brazing furnace (H₂/N₂)	Silver tip brazing to copper carriers	5,000 contacts/hour
Assembly	Labor assembly cells	Mechanism assembly, calibration, testing	3,000 units/day per line
Endurance Testing	Mechanical/electrical life test benches (100,000 cycles)	Life verification, wear monitoring	200 units simultaneous
Environmental Testing	Temperature/humidity chambers, vibration tables	IEC 60068-2 compliance verification	100 units/day

Production Capacity & Lead Times

Product Category	Monthly Capacity	Standard Lead Time	Urgent Order Capability
Compact MPCB (0.63A-25A)	100,000 units	4-5 weeks	3 days (stock components)
Standard MPCB (0.1A-32A)	80,000 units	4-5 weeks	5 days
Power MPCB (10A-63A)	60,000 units	4-5 weeks	7 days
Heavy-duty MPCB (40A-100A)	20,000 units	4-5 weeks	10 days
Electronic MPCB (25A-150A)	20,000 units	4-5 weeks	7 days

Engineering & Technical Team Structure

Department	Personnel	Expertise	Responsibilities
R&D Engineering	5 engineers	Motor protection algorithms, bimetallic materials, electromagnetic design, arc quenching	New product development, thermal modeling, patent portfolio (40+ patents)
Process Engineering	18 engineers	Precision calibration, automated assembly, lean manufacturing, Industry 4.0	Production optimization, SOP documentation, yield improvement (>99.5%)
Testing & Validation	15 engineers	High-current testing, motor simulation, environmental testing, EMC	Type testing coordination (IEC 60947-4-1), failure analysis, certification
Application Engineering	10 engineers	Motor starting calculations, coordination studies, field commissioning	Customer technical support, scheme design, motor protection training
Quality Assurance	30 technicians	ISO 9001, IATF 16949, statistical process control (SPC), metrology	Supplier audit, process audit, corrective action, calibration laboratory

Certifications & Compliance Documentation

Certification	Issuing Body	Scope	Validity
ISO 9001:2015	ZHONGDA HUAYUAN	Quality management system	Annual surveillance
IEC 60947-2 Type Test	SGS	Circuit-breaker performance	Per product series
CE Marking	Notified Body	EU market access	Design-dependent
CCC (China)	CQC	Chinese compulsory certification	5-year validity

Why Our MPCB Manufacturing Stands Apart

Our production facility represents 20 years of specialization in motor protection technology, delivering MPCBs that exceed global standards through:

Vertical integration: In-house bimetallic element production, precision calibration, and electromagnetic coil manufacturing ensuring complete quality control and rapid customization

Advanced calibration technology: 6-station automated calibration systems with temperature chambers (-20°C to +60°C) achieving ±3% trip accuracy across the entire operating range

Testing infrastructure: $3M+ invested in primary injection testing (1000A capacity), 100,000-cycle endurance verification, and comprehensive environmental simulation

Motor-specific expertise: Deep understanding of motor starting characteristics, thermal curves, and coordination requirements with contactors and soft starters

Customization capability: From specialized current settings to unique mounting configurations and auxiliary contact arrangements—engineered to your motor protection requirements

CDADA is a Motor Protection Circuit Breaker manufacturer and supplier in China. Our factory serves diverse industries such as power systems, building automation, and industrial manufacturing, offering flexible OEM/ODM solutions.

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