Applications of Harmonic Commutation for Thyratron Inverters and Rectifiers

The problem of commutation in thyratron rectifiers and inverters is discussed and a method of using a harmonic circuit of reduced kva to force commutation is described. By the aid of harmonic commutation, inverters can be operated to supply lagging loads and rectifiers can be phase controlled in the leading quadrant. A rectifier which is phase controlled 90 degrees leading becomes equivalent to a synchronous condenser and may be used for power factor correction. A duplex type of circuit is described which enables a polyphase inverter to produce a sinusoidal voltage and current, and permits a rectifier to draw a sinusoidal current from the a-c system. The inverter is shown to differ from a synchronous converter only in that the sum of the a-c and d-c armature reactions of the inverter must always be zero. By providing two sets of tubes in the inverter, one on the unity power factor axis and the other on the zero power factor axis, a crossed axis inverter is developed which will furnish a sinusoidal current and voltage for all conditions of load.