STS 300

Centralized Static Transfer Switches
3-phase STS 100-3000 A

Three-phase static transfer switches for seamless load transfer in dual path power systems.

  • Rugged design and high reliability
  • Solutions up to 3000 A
  • Optimized system configuration for ICT applications
  • Customization for harsh environment and specific applications
  • Total control over load transfer: continuous source monitoring and robust management logic guarantee disturbance free power transfers to downstream critical loads.
  • High overload capability: industrial derivation design providing high overload capability and high fault current management.
  • Enhanced safety: redundant control logic and embedded backfeed protection for complete system and operator safety.
  • Minimum maintenance costs: full front accessibility to all components and high material quality extremely reduce servicing.
  • Continuous monitoring of voltage and frequency and automatic instant transfers for secure power switching without cross connection between sources.
  • Short circuit transfer inhibit for robust load protection.
  • SCR fault detection and backfeed protection for maximum upstream safety.
  • Dual manual bypass for complete source independence during maintenance.
  • True oversized neutral (2x In), redundant cooling with monitored fans and redundant (3x3) internal power supply in all system control boards for top product reliability in high availability applications.
  • Full front access for easy maintenance.
  • Bottom and top cable entry for maximum installation versatility.
  • Comprehensive set of communication options for total remote monitoring of equipment operation.
  • Fully compliance with all international product standards for maximum quality guarantee.

Tech Specs

STS 300: Centralized Static Transfer Switches 3-phase STS 100-3000 A

Rating (A)* 100 250 400 630 800 1000 1250
Dimensions WxDxH (mm)** 820x835x1475 1220x860x1900 2000x1000x2100
Weight (kg)** 265 290 305 615 660 1000 1450

*rating up to 3000 A on request **3-pole version


Connection type Hardwired 4w
Nominal voltage 208/380/400/415/440/480 Vac 3-phase with neutral
Voltage tolerance ±10% (up to ±20% on request)
Frequency and range 50/60 Hz, ±2 Hz (up to ±4 Hz on request)
Source harmonic voltage
Unlimited (if THD>20% transfer time ≤10ms)
Transfer phase angle 5° to 30°


Connection type Hardwired 4w
Nominal voltage 208/380/400/415/440/480 Vac 3-phase with neutral
Frequency 50/60 Hz
Transfer time ≤4 ms
Transfer mode Break before make, transfer inhibit on fault
Load power factor 1 to 0.3
Maximum crest factor 3:1
THD current fedback
from load
Overload capacity 125% for 30 min, 150% for 10 min, 200% for 30 s, 2000% for 1 cycle, 4000% for ½ cycle
Efficiency (AC/AC) >99%

Connectivity and function extensions

Front panel Graphical LCD display, mimic LED panel and keyboard
Remote communication Included: dry contact relay card, RS232 and RS485 serial ports,
ModBus-RTU protocol.
Optional: additional dry contact relay card
Optional function extensions 4-pole configuration, plug-in circuit breakers,
operation without neutral,
panel builder execution,
output distribution panels, isolation transformer


Protection degree IP 20 (other options)
Colour RAL 9005 (other options)
Installation layout Wall, back to back and side by side installation allowed
Accessibility Front access, bottom and top cable entry


Operating temperature range 0°C to +40°C
Storage temperature range -10°C to +70°C
Altitude (AMSL) < 1000 m without power reduction, > 1000 m with reduction of 0.5% per 100 m
Audible noise at 1 m (dBA) <62

Standards and certifications

Quality assurance,
environment, health
and safety
ISO 9001, ISO 14001, ISO 45001
Safety IEC/EN 62310-1
EMC IEC/EN 62310-2
Breakers IEC/EN 60947-3
Transfer voltage limits IEEE Standard 446
Protection degree IEC 60529
Performance IEC/EN 62310-3
Marking CE