A general relationship for the input power factor of ac controllers with inductive loads is derived in this paper. Its simplified form is given for the phase angle, integral cycle, and symmetrical pulsewidth modulated controllers. The latter may or may not have a freewheeling path for the load.

Power Factor of AC Controllers for Inductive Loads

This paper shows that the voltage and current harmonics introduced by a single-phase triac ac controller can be significantly reduced by shunting the triac with a fixed-value resistance. Theoretical results are given for a purely resistive load and a fixed RL load with a power factor of 0.7, to substantiate this claim.

Reduction of the Voltage and Current Harmonics Introduced by a Single-Phase Triac AC Controller, by Means of Shunt Resistance

Several configurations of balanced three-phase series RL loads are investigated to consider the feasibility of using thyristor control with integral-cycle triggering. The four-wire star-connected load, with pairs of thyristors in the supply lines and the delta-connection with pairs of thyristors in the load legs, are found to be suitable. Both connections result in similar load voltage and current waveforms. The branch-delta connection is considered to be preferable because the supply lines do not contain DC components of current.

Three-phase circuits with voltage control by integral-cycle single-phase mode triggering of thyristors

The power factor of ac power controller circuits for resistive load drops to small values as the load power is reduced. This paper presents a new ac controller for resistive loads. The new controller has a good power factor for a change in the load power from 100% to 10%. Theoret-ical analysis of the controller circuit as well as experimental results are given.

A New Single Phase Ac Controller For Resistive Loads

of the thesis presented to UFSC as a partial fulfillment of the requirements for the degree of Doctor in Electrical Engineering. PARALLEL OPERATION OF VOLTAGE SOURCE INVERTERS Telles Brunelli Lazzarin

Universidade federal de santa catarina programa de pós-graduação em engenharia elétrica

A number of load waveforms, produced by switching elements in a single-phase supply to a resistance load, are analyzed. The power factor of the circuit is investigated and its relationship to power, distortion factor and fundamental power factor given. A number of particular switching modes are introduced to give leading power factors and certain harmonic elimination.

Steady-State Analysis of Single-Phase AC Controller with Resistance Load

A single-phase, thyristor-controlled resistive or series resistance-inductance load, with sinusoidal supply voltage, has a power factor that can be attributed to a combination of active, reactive (displacement) and distortion voltamperes.

Power Factor of Thyristor-Controlled Loads with Sinusoidal Supply Voltage and Integral-Cycle Triggering

The performance of the saturistor motor is improved by the addition of capacitors in the secondary circuit. The ac performance on run-up is changed considerably with increased torque production,reduced supply current and a power factor nearer to unity. DC dynamic braking is also influenced to the extent of increased braking torque, and reduced run-down times under comparable braking conditions. Braking using capacitor excitation is shown to be improved by the presence of saturistors. Analysis of the various modes of operation is discussed with acceptable prediction of the experimental characteristics.

T. G. Bland

Papers

Steady-State Analysis of Single-Phase AC Controller with Resistance Load

Power Factor of Thyristor-Controlled Loads with Sinusoidal Supply Voltage and Integral-Cycle Triggering

Control of the Saturistor Motor