SKKT 570/18 E: A Technical Review for High-Reliability AC Power Control

SKKT 570/18 E Thyristor/Diode Module Technical Review

High-Current AC Control with SEMIKRON’s SKKT 570/18 E

The Semikron SKKT 570/18 E is a Thyristor/Diode module engineered for high-reliability AC power control in demanding industrial environments. Housed in the robust SEMIPACK® 3 package, it delivers precise and durable performance through its use of pressure contact technology and an isolated metal baseplate. This module’s architecture is focused on providing a dependable solution for line-frequency applications where high current and voltage capabilities are critical.

• Core Specifications: 1800V | 570A | 4000V Isolation
• Key Advantages: High thermal cycling capability, simplified thermal management, and UL recognized reliability.

This design addresses the engineering need for efficient and stable power switching in systems like motor soft-starters without the complexity of high-frequency devices.

Download the Official SKKT 570/18 E Datasheet (PDF)

Technical Analysis: Engineering for Durability

A core feature of the SKKT 570/18 E is its construction using glass passivated thyristor chips. This manufacturing process creates a stable and hermetically sealed junction, providing excellent blocking voltage stability over the module’s lifetime. For design engineers, this translates to predictable performance and reduced aging effects, even in environments with fluctuating temperatures and potential humidity. This robust chip technology is fundamental to the module’s long-term operational reliability in the field.

The module’s thermal design is equally critical. It employs an aluminium nitride ceramic insulated baseplate which offers superior heat transfer compared to conventional materials. The low junction-to-case thermal resistance (Rth(j-c)) of 0.069 K/W per thyristor is a key parameter. This can be thought of as the width of a pipe for heat to escape; a lower value means heat is evacuated more effectively from the silicon chip to the heatsink. This efficiency allows the module to sustain its high 570A average current rating, simplifying heatsink selection and overall thermal management.

Optimized Application Scenarios

The SKKT 570/18 E is engineered for specific high-power, line-frequency applications where its characteristics provide distinct advantages.

• AC Motor Soft Starters: The module’s ability to precisely phase-control high currents allows for smooth voltage ramping, which reduces mechanical stress on motors and drivetrains during startup.
• Controlled Rectifiers: With its 1800V blocking voltage and 570A current rating, it is well-suited for input stages of large DC power supplies and battery chargers, providing reliable AC-to-DC conversion.
• Industrial Temperature Control: In applications like large ovens or chemical processes, the module offers dependable AC power regulation. Its robust thermal design ensures stable operation for precise heating element control.
• Professional Light Dimming: For theaters and studios, the module’s controlled switching provides smooth and flicker-free dimming of high-power lighting systems.

Its high surge current (ITSM) of 15,500A makes it an excellent match for applications with demanding inrush currents and potential fault conditions.

Key Specification Parameters for SKKT 570/18 E

Note: This is a summary. Refer to the official datasheet for complete specifications and operating curves.

Absolute Maximum Ratings (Tvj = 135°C unless otherwise specified)
Repetitive Peak Off-State Voltage (VDRM, VRRM)	1800 V
Average On-State Current (ITAV; sin. 180; Tc=85°C)	570 A
Surge Non-Repetitive On-State Current (ITSM; 10 ms)	15500 A
I²t Value for Fusing (10 ms)	1,201,250 A²s
Electrical & Thermal Characteristics
On-State Voltage Threshold (VT(TO))	0.78 V
Slope Resistance (rT)	0.32 mΩ
Thermal Resistance, Junction to Case (Rth(j-c) per thyristor)	0.069 K/W
Isolation Test Voltage (Visol; 50 Hz, 1 min.)	4000 V
Operating Junction Temperature (Tvj)	-40 to +135 °C

Engineer’s FAQ

What is the primary benefit of the pressure contact system in this module?
The precious metal pressure contact technology ensures a highly reliable electrical and thermal connection between the silicon chip and the terminals. Unlike soldered connections, it is more resilient to failure from thermal cycling, which is a common stress factor in high-power applications. This contributes significantly to the module’s operational longevity and is a key aspect of power module reliability.

How should I calculate the required heatsink for the SKKT 570/18 E?
To determine the appropriate heatsink, you must calculate the total power dissipation and use the module’s thermal resistance values. The datasheet provides the R_th(j-c) (junction-to-case) of 0.069 K/W and R_th(c-s) (case-to-heatsink) of 0.02 K/W. You can calculate power loss based on your load current using the V_T(TO) and r_T values. This allows you to find the maximum allowable thermal resistance of the heatsink to keep the junction temperature below its 135°C limit.

Is this module suitable for high-frequency applications like a VFD?
No, the SKKT 570/18 E is a thyristor (SCR) module designed for line-frequency (50/60 Hz) phase control and rectification. Its turn-off time (t_q) is in the range of 100-200 µs, which is too slow for the high-frequency switching required in a Variable Frequency Drive (VFD). For those applications, an IGBT module would be the appropriate choice.

Enabling Robust Power System Design

The SKKT 570/18 E provides a foundation for durable and efficient high-power AC control systems. Its combination of high current and voltage ratings, a proven housing, and a design centered on thermal stability allows engineers to develop reliable equipment for critical industrial processes. The module’s robust construction ensures consistent performance and a long operational lifespan.