Caledon Controls Ltd
Contact Us Caledon Controls Ltd

Download Area

Buy direct from our online shop

Caledon Controls Ltd
Unit 2 Block 4
Castlehill Ind. Est., Carluke
Scotland ML8 5UF

Tel: +44 (0)1555 773355
Fax: +44 (0)1555 772212


Caledon Controls 25 years



Read Our Privacy Policy Here

Thyristor Stacks for Transformer Loads - STA SERIES



Thyristor Stacks for Transformer Coupled Loads
Click image for larger view


  • Versions for single or 3-phase loads
  • Current rating from 80A to 1000A air cooled
  • Operation without derating up to 50°C ambient
  • Low cost 2-line control of 3-phase load
  • Minimum radio frequency emissions
  • Minimum waveform distortion
  • No power factor degradation
  • Simple installation, commissioning and maintenance
  • Microprocessor controlled
  • Long life ball-bearing fans
  • Compact size, only 290mm deep


This is a range of thyristor stacks, specifically designed for burst fire control of the primary of transformer coupled loads in heating applications. A typical application example is in high temperature furnaces with low resistance graphite heating elements. These stacks switch on near the peak of the voltage waveform, thus minimising transient flux and transformer inrush without recourse to phase angle operation. This technique enables the control of a 3-phase transformer load by switching only two lines, and causes the minimum possible line disturbance, waveform distortion and radio frequency emissions. Special drive techniques ensure the minimum possible rfi associated with zero crossing commutation of the thyristors, enabling the units to be used with confidence in emc compliant systems. The driver control circuit is microprocessor controlled, and accepts either analogue (1-5V, 4-20mA) or logic input signals. A separate enable input is provided, which can be used in conjunction with system interlocks, current overload monitor etc. A logic output is provided for synchronising other thyristors if required. Semiconductor fuses and power supplies are electronically monitored, and an alarm relay is provided for system integration.These units do not have a current limit facility, and are not suitable for use with loads which have a low cold resistance requiring current limiting.

More detailed product information is available on our downloads page


Website Design by DM Web Solutions Ltd ©Caledon Controls Ltd