add wishlist add wishlist show wishlist add compare add compare show compare preloader
  • electro-marker-icon Store Location
  • Currencies
    • AUD
2 Leg Burst Fire SCR Control Advantages

2 Leg Burst Fire SCR Control Advantages

Advanced Energy Logo SmallFastron Electronics Logo

Advantages of 2 Leg Control for 3 Wire, 3 Phase Systems using Burst Fire Control Method

2 Leg Wiring

Requirement for 2 Leg Control Method

  • Burst Fire Control is Acceptable
  • 3 Phase 3 Wire system

2 Leg Control Can Not be used in the following configurations

  • 4 Wire System
  • 3 Wire Inside Delta Wiring Arrangement
  • Phase Angle Control
  • Hybrid Phase/Burst Control

5 Main Advantages to 2 Leg Control

  • High Efficiency/Economical – 33% less losses due to only switching two legs. The load current passes through 4 SCR’s instead of 6.
  • Lower heat dissipation – Since we are only switching 2 legs, then the heat dissipation if 33% less than switching all three legs
  • Safety – 3 Lage and 2 Leg Controllers have the same level of safety as both require a mechanical Contactor for safety disconnect. This is a clear requirement for the National Electricity Code since SCR’s are not considered a complete disconnect.
  • Lower EMC and Harmonics due to having one phase connected at all times. This reduces potential clipping when one phase turns on while there is no return current path. 2 Leg Control generates less noise and harmonics than both 3 Phase Burst and Phase Angle Control


We Highly Recommend the use for 2 Leg Control for Open Delta, or 3 Wire Star applications using Burst Fire control, and in particular in EMC/Harmonics sensitive environments.

Reference of SCR Controller Wiring Topologies

Single Phase and 2 Leg

Single and 2 Leg Wiring Methods

Three Phase Star

3 Wire Star

Three Phase Delta

Delta Wiring Methods

Daniel Rehe
M.D. Fastron Electronics
Eng, Electronics RMIT

Download a PDF Copy of this article

Thyro A Series Quick Setup Guide

BasicBus Comms Setup Guide

Anybus Setup Guide (Ethernet IP)

Images copywrite - Advanced Energy © 2019