STS300: STS 100 – 800 A 3 phase

3-phase STS 100-800 A

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

  • Rugged design and high reliability
  • Solutions up to 3000 A
  •  Other ratings under request
  • Optimised 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
  • 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 (3×3) internal power supply in all system control boards for top product reliability in high availability applications
  • Short circuit transfer inhibit for robust load protection
  • 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

STS300 technical data

Rating (A) 100 250 400 630 800
Dimensions WxHxD (mm) 820x1475x835 1220x1900x860
Weight (kg) 265 290 305 615 660


Connection type Hardwired 2w
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 (>20%THD transfer time ≤10ms)
Transfer phase angle 5° ÷ 30°


Connection type Hardwired 2w
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 unlimited
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 SPDT contact relay board; RS232 and RS485
serial ports, ModBus-RTU protocol;
optional: additional SPDT contact relay board
Optional function extension 4-poles configuration; plug-in circuit breakers; operation without neutral;
panel builder execution; output distribution panels; isolation transformer


Protection degree IP 20 (other options)
Colour RAL 7035 (other options)
Installation layout Wall, back to back and side by side installation allowed
Accessibility Front access, bottom and top cable entry

Other features


Operating temperature range 0 °C ÷ +40 °C
Storage temperature range -10 °C ÷ +70 °C
Altitude <1000 m
Audible noise at 1m (dBA) <62

Standards and certifications

Quality assurance, environment, health and safety ISO 9001:2008, ISO 14001:2004, GOST, BS OHSAS 18001:2007
Safety IEC EN 62040-1
EMC IEC EN 62040-2
Breakers IEC EN 60947-3
Transfer voltage limits IEC EN 62040-3 IEEE Standard 446
Protection degree IEC 60529
Marking CE