Additional features
Network frequency	50/60 Hz
[Ue] Operational rated voltage	380 - 415 V AC 50/60 Hz; 125 V DC;
Magnetic trip threshold	4 x In
[Ics] Rated operational breaking capacity	37.5 kA 75 % corresponds to EN/IEC 60947-2 - 220 - 240 V AC 50/60 Hz; 75 kA 75 % corresponds to EN/IEC 60947-2 - 110 - 130 V AC 50/60 Hz; 9.37 kA 75 % corresponds to EN/IEC 60947-2 - 380 - 415 V AC 50/60 Hz; 50 kA 100 % corresponds to EN/IEC 60947-2 - 60 V DC; 50 kA 100 % corresponds to EN/IEC 60947-2 - 125 V DC
[Ui] Rated insulation voltage	690 V AC 50/60 Hz complies with EN/IEC 60947-2
[Uimp] Rated impulse voltage withstand	8 kV corresponds to EN/IEC 60947-2
Control type	Toggle switch; Manual trip test
Local signalling	Trip indicator; ON/OFF indicator
Mounting mode	Plug-in
Mounting position	Vertical
Mounting bracket	35 mm symmetrical DIN rail
9-mm pitch	3
Height	103 mm
Depth	81 mm
Width	27 mm
Product weight	0,24 kg
Mechanical life	20000 cycles
Electrical lifetime	10000 cycles
Provisions for padlocks	Lockable
Description of locking options	Integrated locking
Connections - terminals	Tunnel terminals 1.5…50 mm² solid; tunnel terminals 1…35 mm² stranded
Wire stripping length	20 mm
[M] tightening torque	3,5 Nm
Earth fault protection	None
Contact position indicator
Compatibility of comb rails and distribution blocks
Contractual warranty
Warranty (in months)	18
Main features
Product series	Acti9
Product name	Acti9 NG125
Product or component type	Miniature circuit breaker (MCB)
Device short name	NG125L
Device application	Distribution
Pole description	1P
Number of protected poles	1
[In] Rated current	40 A at 40 °C
Type of network	AC; DC
Trigger technology	Thermal-magnetic
Cam disc	B
Breaking capacity	50 kA Icu at 220 - 240 V AC 50/60 Hz complies with EN/IEC 60947-2; 100 kA Icu at 110 - 130 V AC 50/60 Hz complies with EN/IEC 60947-2; 50 kA Icu at 12 V DC complies with EN/IEC 60947-2; 50 kA Icu at 125 V DC complies with EN/IEC 60947-2; 36 kA Icu at
Application category	Category A corresponds to IEC 60947-2
Suitability for insulation	Yes, complies with IEC 60947-2
Standards	EN/IEC 60947-2
Mounting
Degree of protection (IP)	IP20 complies with IEC 60529
Degree of protection (IK)	IK05 corresponds to EN/IEC 62262
Pollution degree	3 corresponds to IEC 60947-2
Over voltage category	IV
Drip-proof	2 corresponds to IEC 60068-1
Relative humidity	95 % at 55 °C
Operating altitude	2.000 m
Operating ambient temperature	-30…70 °C
Ambient temperature during storage	-40…70 °C
Packaging units
VPE 1 type	PCE
Number of devices per package	1
VPE 1 height	3 cm
VPE 1 width	8,3 cm
VPE 1 length	11,1 cm
Packaging weight (Lbs)	232 g
VPE 2 type	BB1
VPE 2 quantity	12
VPE 2 height	9,1 cm
VPE 2 width	12,1 cm
VPE 2 length	36,1 cm
VPE 2 weight	2,794 kg
VPE 3 type	S03
VPE 3 quantity	72
VPE 3 height	30 cm
VPE 3 width	30 cm
VPE 3 length	40 cm
VPE 3 weight	17,251 kg

The NG125L circuit breaker from the Acti9 series by Schneider Electric is a 1-pole line protection switch designed for distribution in electrical installations. It provides protection against overload currents and short-circuit currents and is rated for operating voltages of 380–415 V AC and 125 V DC. The rated current is 40 A at an ambient temperature of 40 °C. The tripping technology is based on a thermomagnetic principle, with the B curve defining the tripping characteristic. This means the switch trips after a time-dependent thermal reaction under continuous overload current and reacts immediately via magnetic effect to sudden short-circuit currents. The magnetic tripping threshold is set at 4 times the rated current (4 x In), enabling rapid response to high fault currents.

Applications

The switch is suitable for use in industrial and commercial electrical installations, particularly in distribution systems where reliable protection is required. It complies with usage category A according to IEC 60947-2, making it suitable for installations with low power supply and low short-circuit current. The insulation capability is certified according to IEC 60947-2, enabling use in installations with higher insulation requirements. The rated insulation voltage is 690 V AC, ensuring high electrical strength. The rated impulse voltage withstand of 8 kV protects the device against transient voltage surges.

Functions and Equipment in Detail

The device features a contact position indicator that visually signals the ON/OFF state. A red mechanical indicator on the front panel shows the tripping status, enhancing operational safety. An integrated test button allows manual testing of the tripping mechanism to ensure functionality. Control is via a toggle switch, enabling clear operation. Local signaling includes the tripping indicator and the ON/OFF indicator, making the operating status immediately visible.

Technology Explained Simply

The thermomagnetic tripping technology combines two protection principles: the thermal component reacts to sustained overloads by deforming a bimetal strip when heated, triggering the switch. The magnetic component reacts instantly to high short-circuit currents by actuating an electromagnet to trigger the tripping mechanism. The snap-action switching ensures wear-free contact switching, increasing service life. The mechanical life is 20,000 cycles, and the electrical life is 10,000 cycles, indicating high operational reliability.

Compatibility and Accessories

The switch is designed for mounting on a 35 mm symmetrical DIN rail and is suitable for vertical installation. Compatibility with comb rails and distribution blocks enables flexible integration into existing distribution systems. Various accessories are available, including overload release units (e.g. 19064, 19066), undervoltage release units (e.g. 19061, 19067), auxiliary switches (e.g. 19071, 19072), interlocking elements (e.g. 19090), and multiple connection terminals (e.g. 19091, 19096). These modules can be optionally connected to enable additional functions such as fault tripping, signaling, or remote control.

Mounting and Installation

Mounting is on a 35 mm DIN rail, with vertical orientation specified. Connections are made via tunnel terminals designed for solid cable 1.5 to 50 mm² and flexible cable 1 to 35 mm². The required wire stripping length is 20 mm, and the tightening torque for the terminals is 3.5 Nm. Power supply is possible from both top and bottom, providing flexible installation options. The integrated interlock allows the fitting of padlocks to secure the switch against unintended operation.

Operational Advantages

The switch is characterized by high operational reliability, supported by clear signaling and an integrated test function. The thermomagnetic tripping technology ensures precise protection against overload and short-circuit. The high mechanical and electrical life reduces maintenance and replacement intervals. Compatibility with various accessory modules extends functionality and enables customized adaptation to specific requirements. The operating temperature range of -30 °C to 70 °C and storage temperature of -40 °C to 70 °C make the switch suitable for a wide range of operating conditions. The protection rating IP20 and IK05 protect against mechanical impacts and contact with hazardous parts, while pollution degree 3 and overvoltage category IV cover additional safety aspects. The operating altitude is up to 2,000 m above sea level, suitable even for installations in mountainous regions. The relative humidity of 95 % at 55 °C demonstrates tolerance to humid environments.