Content last revised on April 14, 2026
SKR 320/04 Semikron Rectifier Diode: 400V 320A Stud-Mount Reliability
The SKR 320/04, part of Semikron's robust stud diode family, is a high-reliability discrete rectifier diode that delivers unmatched thermal stability and exceptional surge current endurance for high-stress line-frequency applications. Rated at 400V and 320A, with an ultra-low Rth(j-c) of 0.16°C/W and a massive IFSM of 9000A, it readily withstands punishing electrical transients. What makes the SKR 320/04 resilient against environmental degradation? The hermetic metal case with a glass insulator completely seals the silicon from corrosive elements. Its threaded M24x1.5 design guarantees formidable mechanical mounting, effectively neutralizing risks in high-vibration industrial deployments. For 400V front-end rectifiers prioritizing surge resilience, this 320A stud diode is the optimal choice.
Key Parameter Overview
Decoding the Specs for Enhanced Thermal Reliability
The following functional breakdown highlights the core electrical and physical ratings that define the operational safety envelope of the SKR 320/04.
| Functional Group | Parameter | Value | Condition / Note |
|---|---|---|---|
| Voltage & Current Limits | Repetitive Peak Reverse Voltage (VRRM) | 400V | Continuous operation limit |
| Average Forward Current (IFAV) | 320A | sin. 180°, Tc = 120°C | |
| Surge Forward Current (IFSM) | 9000A | Tvj = 25°C, 10ms | |
| Fusing Integral (I²t) | 405,000 A²s | Tvj = 25°C, 8.3...10ms | |
| Thermal & Mechanical | Thermal Resistance Junction-to-Case (Rth(j-c)) | 0.16 K/W | Direct cooling efficiency |
| Operating Junction Temp (Tvj) | -40°C to +180°C | Wide operating window | |
| Mounting Torque | 60 Nm | M24x1.5 Stud (48 Nm if lubricated) | |
| Static Characteristics | Forward Voltage Drop (VF) | 1.35V max | Tvj = 25°C, IF = 1000A |
| Device Polarity | Cathode to Stud | Indicated by the "SKR" prefix |
Download the SKR 320/04 datasheet for detailed specifications and performance curves.
Application Scenarios & Value
Mastering Inrush Currents in Heavy-Duty Industrial Motor Drives
Engineers consistently face component degradation during the initial spin-up of heavy-duty industrial motors, primarily due to devastating inrush current transients. The SKR 320/04 is strategically structured to neutralize this specific threat within a front-end rectifier stage. By leveraging an extraordinary IFSM rating of 9000A, the silicon die safely absorbs the massive thermal shock generated during a 10ms surge event. This prevents localized hotspot formation and ensures the continuity of the line-frequency power conversion process without triggering protective shutdown sequences.
Furthermore, the robust continuous current capability of 320A at a high case temperature of 120°C minimizes the reliance on oversized, expensive cooling architectures. While the SKR 320/04 serves perfectly for rugged, individual phase rectification in 400V grid networks, designs demanding an integrated solution for higher voltage lines might benefit from evaluating the MDS500A/1600V three-phase bridge module.
Technical Deep Dive
Unpacking the Hermetic Stud Architecture and Heat Dissipation
The mechanical architecture of the SKR 320/04 fundamentally dictates its electrical durability. The active silicon wafer is entirely encapsulated within an E16 hermetic metal case featuring a specialized glass insulator. Think of this hermetic sealing as a submarine's pressure hull—it completely isolates the internal semiconductor micro-structures from harsh, corrosive external environments, eliminating the ingress of moisture or airborne industrial particulates that routinely compromise non-hermetic alternatives over time.
Beyond baseline environmental protection, the M24x1.5 threaded stud executes a critical function in system thermal management. Extracting maximum performance and achieving the ultra-low Rth(j-c) of 0.16 K/W requires a continuous, flawless interface between the diode case and the heatsink. The threaded stud operates like an industrial anchor, sustaining a tightening torque of up to 60 Nm. This immense clamping force securely fastens the device under extreme mechanical vibrations, preventing thermal runaway caused by microscopic air gaps. Finally, the "SKR" nomenclature indicates a Cathode to Stud polarity. This distinct polarity structure allows designers to bolt multiple SKR units directly onto a single, non-isolated heatsink to form the common positive rail of a bridge converter, drastically shrinking the total volume of the thermal solution.
Frequently Asked Questions
Addressing Core Engineering Concerns
- How does the cathode to stud polarity (SKR) influence my heatsink design compared to the SKN variant?The SKR prefix designates the device's threaded stud as the cathode terminal. In a typical bridge rectifier topology, this configuration allows multiple SKR 320/04 diodes to be directly fastened onto a shared heatsink that inherently functions as the positive DC output rail. This removes the necessity for individual isolated thermal pads, immediately enhancing direct heat transfer and drastically simplifying your mechanical assembly process.
- What is the critical significance of the 405,000 A²s I²t rating for my overcurrent protection circuitry?The massive I²t rating of 405,000 A²s fundamentally dictates the required clearing time for your fast-acting semiconductor fuses. It establishes a precise thermal energy ceiling, guaranteeing that during a hard short-circuit fault, a properly sized fuse will rupture milliseconds before the internal silicon junction temperature surpasses its catastrophic destruction threshold of 180°C.
To secure authentic SKR 320/04 components for your next high-surge rectification project or to discuss volume pricing parameters, contact our technical sales team for immediate stock verification.
