An improved apparatus for the measurement of the power factor of electric alternating current circuits, more especially designed for remote measuring purposes

摘要

507,287. Power-factor measurements. LANDIS & GYR AKT.-GES. Oct. 22, 1938, No. 30624. Convention date, Oct. 22, 1937. [Class 37] A power-factor meter comprises a Ferraris meter 10 having one driving winding 11 supplied from the secondary voltage of a phase regulator 9 operated by a phase-controlling apparatus 1, the other driving winding 12 and the brake winding 13 being connected across the supply mains R, T. The phase-controlling apparatus 1 comprises a wattmeter having two measuring systems 2, 2SP1/SP of which the current coils'3, 3SP1/SP are connected in the phase conductors R, T of the polyphase network R, S, T and the voltage coils 7, 7SP1/SP are connected to the secondary winding 8 of the phase regulator 9. The movable primary winding 16 of the phase regulator 9 is coupled through reduction gearing 17 with the rotor 18 of an auxiliary motor 19 having two field windings 20, 21 connected to fixed contacts 23, 24 and a movable contact 22 actuated by the wattmeter 1. At a particular value of the power-factor the contact 22 is stationary in its mid position and the motor 19 is not energized, so that the primary winding 16 remains stationary. The rotor 26 of the meter 10 then turns at a velocity proportional to the sine of the phase displacement, when the driving system is so adjusted that it is stationary at unity power' factor. Change of power factor causes the wattmeter 1 to move the contact 22 to engage one of the contacts 23, 24 so that the corresponding winding 20 or 21 is energized. The primary winding 16 is thereupon turned until the difference of phase between the driving fields of the wattmeter 1 is again neutralized and the contact 22 is returned to its mid-Position. The voltage driving field produced by the driving winding 11 of the meter 10 is then altered in phase by the same amount as the voltage driving field of the wattmeter 1, and the speed is correspondingly altered. A variable resistance 31 in series with the winding 11 enables the phase relation between the two voltage fluxes of the meter 10 to be adjusted so that at any definite power factor any predetermined speed of rotation may be selected. The rotor 26 may transmit impulses through brushes 15 for remote measurement. In a moditication the auxiliary motor 19 and the contacts 22, 23, 24 are omitted and the phase controlling apparatus 1 is directly coupled with the phase regulator 9.