Hager HMF399T Miniature Circuit Breaker MCB 125A 3 Pole C Curve 10kA 4.5 Module DIN Rail 415V

Description

The 125A three-phase high-current MCB.

The Hager HMF399T is a 125A three-pole high-current miniature circuit breaker (MCB) with a C tripping curve and 10kA breaking capacity, the top of the three-phase HMF range, protecting sub-mains and heavy distribution from a 4.5-module DIN rail body.

Key Features

• Rated current: 125A, three-phase (3P)
• C tripping curve (5–10x In)
• 10kA breaking capacity (Icn) to IEC 60898-1; Icu 10kA to IEC 60947-2
• Rated voltage 415V AC, insulation voltage 500V
• 4.5-module width (80mm) DIN rail mount
• High-capacity terminals: rigid to 70mm², flexible to 50mm²
• Rated impulse withstand voltage 6000V; IP20
• Compliant with AS/NZS 60898.1 and AS/NZS IEC 60947-2

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Why it Matters

Top of the three-phase high-current range.
The HMF399T is a 125A three-pole miniature circuit breaker, the largest in Hager's high-current HMF range, protecting all three phases of a circuit against overload and short circuit and tripping automatically when either occurs. At 125A across three poles it is built for the heaviest three-phase sub-mains and general distribution – feeding sub-boards, large machinery and high-demand three-phase loads – while still mounting on standard DIN rail rather than requiring a moulded-case breaker.

C curve and genuine cable capacity.
The C tripping characteristic trips on short circuit at 5 to 10 times rated current, the general-purpose curve for mixed resistive and inductive loads including motors and high inrush. Backed by a 10kA short-circuit breaking capacity to IEC 60898-1 (Icu 10kA to IEC 60947-2, with a 75% Ics service breaking capacity), its high-capacity terminals accept rigid conductors up to 70mm² and flexible up to 50mm² per pole at a 3.5 to 5.0Nm torque – matching the heavy cable a 125A three-phase feed runs.

Built for Australian switchboards.
At 4.5 modules (80mm) wide, 90mm high and 70mm deep, the HMF399T mounts on standard 35mm DIN rail with 360° mounting flexibility. It is compliant with AS/NZS 60898.1 and AS/NZS IEC 60947-2, rated IP20, and operates from -25°C to 70°C to suit main and sub-distribution boards across Australian conditions. At this rating heat is significant, so plan board ventilation and spacing and consider an LZ060 heat dissipation insert; MZN130 terminal cover, MZN175 locking kit and MZ auxiliaries are also available.

Q: Is the Hager HMF399T a three-phase breaker?
Yes. It is a 3-pole (3P) MCB that protects all three phases of a 415V circuit; it does not include a separate neutral pole, so a 3P+N model is needed where neutral switching is required.

Q: What cable can the HMF399T terminals take?
Rigid conductors up to 70mm² and flexible up to 50mm² per pole, tightened to between 3.5 and 5.0Nm – sized for a 125A three-phase sub-main.

Q: What does the 10kA rating mean on the HMF399T?
10kA is the rated short-circuit breaking capacity (Icn) to IEC 60898-1 – the maximum fault current the breaker can safely interrupt – with Icu 10kA and a 75% service breaking capacity (Ics) to IEC 60947-2.