Introduction
In industrial power distribution systems, high-capacity circuit breakers are the core protective components of main incoming cabinets and large distribution cabinets. The Megatiker M4 series launched by BTicino, as an important component of the Megatiker platform, is designed specifically for current levels ranging from 250A to 630A, providing a breaking capacity of up to 100kA, meeting the dual requirements of high reliability and flexibility in industrial power distribution.
This article is based on the official technical documentation of BTicino, systematically reviewing the technical characteristics, electrical parameters, installation methods, accessory configurations, and trip characteristics of Megatiker M4 thermal magnetic circuit breaker and MS4 isolating switch, providing professional reference for engineers and system integrators.
Product positioning and scope
1. Product positioning
The Megatiker M4 platform is positioned in the high-end industrial power distribution market and has the following characteristics:
High power applications: rated current covering 250A to 630A
High segmentation capability: up to 100kA
Flexible installation: supports multiple installation methods including fixed, plug-in, and pull-out
Rich attachments: supports multiple functions such as leakage protection, electric operation, interlocking, etc
2. Product Scope
Thermal magnetic circuit breaker
According to different breaking capabilities, M4 circuit breakers are divided into four levels:
Breaking ability level, model code, breaking ability Icu (415V AC), number of poles
F (36kA) T743Fxxx / T744Fxxx / T742Fxxx 36 kA 3P / 4P / 3P+N/2
N (50kA) T743Nxxx / T744Nxxx / T742Nxxx 50 kA 3P / 4P / 3P+N/2
H (70kA) T743Hxxx / T744Hxxx / T742Hxxx 70 kA 3P / 4P / 3P+N/2
L (100kA) T743Lxxx / T744Lxxx / T742Lxxx 100 kA 3P / 4P / 3P+N/2
Rated current level: 250A, 320A, 400A, 500A, 630A
disconnecting switch
MS4 isolation switch is suitable for isolation applications that require visible breakpoints:
Rated current 3P model 4P model
400A T743S400 T744S400
630A T743S630 T744S630
Size and weight
The M4 series adopts a modular design for easy panel installation:
Parameters 3P 4P
Width (W) 140 mm 183 mm
Height (H) 260 mm 260 mm
Depth (D) 105 mm 105 mm
Pole spacing 42 mm 42 mm
Weight Reference
Component 3P weight (kg) 4P weight (kg)
Fixed circuit breaker 5.20 6.85
Fixed isolation switch 5.00 6.40
Plug in accessory (front wiring)+3.35+4.29
Plug in accessory (rear wiring)+3.55+4.79
Pull out attachment+2.30+5.50
Supply content and installation method
1. Factory standard configuration
Each M4 circuit breaker comes with the following accessories at the factory:
Fixed screws (4 for 3P, 4 for 4P)
Wiring screws (6 for 3P and 8 for 4P)
Interphase insulation partitions (2 pieces for 3P, 3 pieces for 4P)
2. Installation method
The circuit breaker supports the following installation directions:
Vertical installation: standard installation method
Horizontal installation: suitable for cabinets with limited space
Reverse feeding: Supports upper or lower input lines, no LINE/LOAD marking required for reverse feeding
3. Installation form
Fixed type: directly installed on the panel
Plug in: Installed through a dedicated base for quick replacement
Pull out type: equipped with a "Debro lift" mechanism, supporting live plugging and unplugging, with three positions for connection, testing, and disconnection

Electrical and mechanical characteristics
1. Technical parameters of circuit breaker
Parameter values
Rated current In 250/320/400/500/630 A
Pole number 3P/4P/3P+N/2
Rated insulation voltage Ui 800 V AC
Rated working voltage Ue 690 V AC
Rated impulse withstand voltage Uimp 8 kV
Rated frequency 50/60 Hz
Reference ambient temperature 40 ° C/50 ° C
Working temperature range -25 ° C to+70 ° C
Mechanical lifespan of 20000 cycles
Mechanical lifespan (with electric operation) 10000 times
Electrical lifespan (In) 4000 times
Electrical lifespan (0.5 × In) 8000 times
Use category A
Suitable for isolation is
2. Protection features
Overload protection (thermal): adjustable range from 0.8 to 1 × In
Short circuit protection (magnetic): adjustable range 5 to 10 × In
Neutral wire protection: The 4P version provides 100% phase pole protection
3P+N/2 version: The neutral wire protection current is 50% of the phase pole
3. Technical parameters of isolation switch
Parameter 400A model 630A model
Rated uninterruptible current Ie 400 A 630 A
Short time withstand current Icw (1s) 5 kA 8 kA
Rated short-circuit connection capacity Icm 8 kA 14 kA
Use category AC23A AC22A
Is it suitable for isolation
Mechanical lifespan 20000 cycles 20000 cycles
Electrical lifespan 4000 times 4000 times
Breaking ability and current limiting characteristics
1. Breaking ability (Icu)
The breaking capacity of M4 circuit breaker at different voltage levels is as follows:
Voltage 36kA (F) 50kA (N) 70kA (H) 100kA (L)
240V AC 70 kA 100 kA 105 kA 150 kA
415V AC 36 kA 50 kA 70 kA 100 kA
500V AC 25 kA 30 kA 40 kA 50 kA
690V AC 14 kA 18 kA 20 kA 22 kA
250V DC 35 kA 35 kA 35 kA 35 kA
2. Operating short-circuit breaking capacity (Ics)
F/N/H level: Ics=100% Icu
L level: Ics=70% Icu