GB788058A - Electrostatic precipitator supply control circuits - Google Patents

Abstract

788,058. Automatic control systems for electrostatic precipitators. AIR PREHEATER CORPORATION. July 28, 1954 [Aug. 17, 1953], No. 22029/54. Class 38 (4). [Also in Group XXXIX] In an electrostatic precipitator supply control circuit wherein a bank of precipitator electrodes is charged with high direct voltage from a rectifier 53 connected across the secondary winding 52 of a transformer whose primary winding 51 is fed by an A.C. supply in a circuit which includes saturable power reactors 60, 70, to regulate the energy transfer of the transformer the energizing current of the power reactors is controlled by saturable control reactors 62, 63, 89 having windings which are subjected to the state of operation of the precipitator. The main windings of the power reactors 60, 70 are connected respectively in series and in parallel with the primary winding 51 and their energizing windings 61 and 71 ... 73 are energized respectively in opposite relation to each other. Energizing windings 61 are fed, from an auxiliary A.C. supply at 69 via control reactor control windings 64, a rectifier 64B and D.C. feedback windings 65,'with a direct current which depends on the control currents in further control windings 66 ... 68 of the reactors 62, 63; serially connected windings 66 are connected between earth and an adjustable tapping on a resistor 54 connected between earth and the earthed side of rectifier 53 while serially connected windings 67 are connected between earth and an adjustable tapping or a resistor 55 connected between the precipitator high voltage electrode and earth, and the two sets of windings 66, 67 are stated to be responsive respectively to the current and voltage of the electrode and act in opposite senses whereby when a flash-over occurs their magnetization, which opposes that of windings 65, greatly increases to " snap-off " the excitation of reactors 60 and reduce the precipitator power to below flashover level. Rotating in synchronism with a precipitator electrode cleaning pipe, not shown, is a disc 80 disposed in the gap of a magnetic pick-up 81 and of which only an edge sector 82 is of ferro-magnetic material, and serially connected windings 68 of the control reactors are fed from an auxiliary A.C. source at 84 via a .winding 83 on the pick-up 81 and a rectifier 85; during the cleaning period of the electrode bank to which the circuit is connected the sector 82 is in the gap of pick-up 81 and the resulting increased control current reduces the power level of that bank. Power reactor 70 is connected to a similar pick-up 75 also to reduce the electrode voltage during cleaning. Specifications 684,024, 684,025, [both in Group XL (a)], 723,568, 728,474, and 756,760 are referred to.