Power Phase Angle

In phase-angle control, each SCR of the back-to-back pair is turned on for a variable portion of the half-cycle that it conducts. Power is regulated by advancing or delaying the point at which the SCR is turned ON within each half cycle. Light dimmers are an example of phase-angle control.

Phase-angle control provides a very fine resolution of power and is used to control fast responding loads such as tungsten-filament lamps or loads in which the resistance changes as a function of temperature. Phase-angle control is required if the load is transformer-coupled or inductive.

Power Phase Angle Controllers

Phase-angle controllers are typically more expensive than zero-cross controllers because the phase-angle circuit requires more sophistication than does a zero-cross circuit. Phase-angle control of three-phase power requires SCR's in all three legs and is appreciably more expensive than zero-cross control which only requires SCR's in two of the three legs.

Model	Phases	Firing Mode	Output	Current Low	Current High	Highlights
MicroFUSION Single Phase	Single phase	Phase angle, Zero cross, Zero Cross Transformer Mode, Fast Zero Cross	AC	8	400	MicroFUSION is an ultra-compact high performance digital SCR controller that adapts to the analog environment as well as the digital environment.
MicroFUSION Three Phase	Three phase	Phase angle, Zero cross, Zero Cross Transformer Mode, Fast Zero Cross	AC	8	400	MicroFUSION is an ultra-compact high performance digital SCR controller that adapts to the analog environment as well as the digital environment.
FUSION Single Phase (AC) Power Controller 500 - 1200A	Single phase	Phase angle, Zero cross, Fast Zero Cross	AC	500	1 200	24 - 600 Vac. A microprocessor-based SCR controller operating both analog and digital interfaces. A phase angle or zero cross fired controller which linearly controls, with respect to the setpoint, the AC voltage, current, or true power applied to an electrical load. Control is achieved by means of a pair of inverse parallel SCRs.
FUSION Three Phase (AC) Power Controller 500 - 1200A	Three phase	Phase angle, Zero cross, Fast Zero Cross	AC	500	1 200	24 - 600 Vac. A microprocessor-based SCR controller operating both analog and digital interfaces. A phase angle or zero cross fired SCR controller which linearly controls, with respect to the setpoint, the AC voltage, current, or true power applied to a three phase electrical load. The 3 phase controller can be ordered in either 2 or 3 leg control with 2 leg being limited to zero cross firing. Control is achieved for 3 leg by three pairs of inverse parallel SCRs or in 2 leg by 2 pairs of inverse parallel SCRs.
FUSION Single Phase (DC) Power Controller	Single phase	Phase angle	DC	45	1 080	24 - 600 Vac. A microprocessor-based DC SCR controller operating both analog and digital interfaces. A phase angle fired controller which linearly controls, with respect to the setpoint, the DC voltage, current, or true power applied to an electrical load. Control is achieved by means of a half controlled SCR bridge.
FUSION Three Phase (DC) Power Controller	Three phase	Phase angle	DC	60	1 400	24 - 600 Vac. A microprocessor-based DC SCR controller operating both analog and digital interfaces. A phase angle-fired controller which linearly controls, with respect to the setpoint, the DC voltage, current, or true power applied to an electrical load. Control is achieved by means of a six SCR bridge with freewheeling diode.