Patent GB-1182652-A (GB)
Title: Improvements in Power Converter Employing Integrated Magnetics
Inventor: MORGAN RAYMOND EVAN
IPC: H02M3/10
Filed: 1967-04-10
Abstract: 1,182,652. Converting; supply systems for consuming apparatus. GENERAL ELECTRIC CO. 10 April, 1967 [20 May, 1966], No.16347/67. Headings H2F and H2H. [Also in Division H1] A power converting system is characterized in that a single transformer is arranged to provide all the inductances required in the circuit, e.g. for commutating, filtering or cushioning. Fig. 1 shows an inverter using a transformer 33 provided with two centretapped primary windings 34 and 35, and a centre-tapped secondary winding 36. When thyristor 15 is turned on, capacitor 27 discharges through it and throughthe primary winding half 34a which has a leakage inductance such that it resonates with the capacitor at the commutating frequency. When the charge on capacitor 27 reverses, the charge on it will oscillate with that on the main commutating capacitor 23 through the winding half 34b, and when capacitor 23 reverses its charge the diode 24 conducts to apply reverse bias across thyristor 15 and turn it off. Capacitor 23 limits the rate of rise of voltage across thyristor 15 when it is turned off, and leakage inductance limits the rate of rise of current through the thyristor when it is turned on. A feedback diode 37 is arranged in parallel with the thyristor, and a clamping diode (54, Fig. 6, not shown), may be connected in series with it to the other D.C. supply terminal 19. When the direction of power flow may need to be reversed, an oppositely polarized thyristor (15 2 , Fig. 13, not shown), is connected in parallel with the thyristor 15 and its control electrode is connected to a point on a parallel circuit comprising a resistance (81), a diode (82), and a second resistance (83). The circuit may be adapted for three-phase operation, (Fig. 12, not shown). In a modified circuit, (Fig. 5, not shown), using a transformer without centretaps on the primary windings, the capacitors 23 and 23<SP>1</SP> are connected together through a non-capacitive impedance element (48). Power control circuit.-Fig. 7 illustrates a chopper circuit for controlling the power supplied to a load 22 by controlling the frequency at which thyristor 15 is turned on. When the thyristor is turned on, conduction through the coasting rectifiers 17a and 17b stops, and energy trapped in winding 16 is directed into the commutating capacity 27 which resonates with the winding at the commutating frequency. When the charge on capacitor 27 reverses the capacitor oscillates with capacitor 23 and resonant winding 26, and the capacitor 23 applies reverse bias to the thyristor 15 through diode 24. The transformer 55 may alter the supply voltage to the load by auto-transformer action. In a simpler circuit, (Fig. 8, not shown), capacitor 27, diode 24, and windings 16 and 26 are omitted, and the diodes 17a and 17b are replaced by a single diode (17) connected between the thyristor 15 and the negative supply terminal 19. This circuit may be modified by including a commutating thyristor (57<SP>1</SP>). Inverters.-Fig. 9 shows an inverter circuit with commutating capacitors 23 and 23<SP>1</SP> which resonate with winding 62b. In a modified circuit, (Fig. 10, not shown), the turn on of one thyristor will result in the other being turned off, and in another modification, (Fig. 11, not shown), separate commutating thyristors are provided. The circuits described may be modified to employ diacs or triacs, the former being triggered by a high speed pulse.