Buck-boost transformer and PWM topology help OEMs operate equipment in countries with mains fluctuating outside design limits

Technology	Advantages	Drawbacks
Electromechanical	• Precise regulation •  Low impedance •  Excellent stability •  High efficiency	• Correction takes seconds • Voltage overshoots following mains cycling •  Requires periodic replacement of brushes •  Manual bypass only •  Complex design
Electronic Tap-switching	• Low cost •  High efficiency •  Low impedance	• Slow correction Average reliability • Coarse regulation • Interrupts load current when switching •  Complex internal wiring Manual bypass only
Dual Conversion	• Precise regulation •  Fast regulation •  No switching of power path •  Energy storage •  Corrects frequency variations	• Very High cost Very Poor efficiency • Must be oversized for high-inrush loads • Complexity • Reliability
High-speed PWM VRp	• Precise regulation •  Fast regulation •  High efficiency •  Low impedance •  No switching of power path •  Simple design •  Automatic bypass   •  Reasonable cost	• No energy storage • Does not correct frequency variation