Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Patent
1994-12-20
1998-02-03
Karlsen, Ernest F.
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
324108, G01R 3134, G01R 2500
Patent
active
057148899
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/FI93/00267, filed Jun. 22, 1993.
The object of the invention is a method and measuring device for measuring the direction of rotation of a three-phase system, the measurement being carried out by means of measuring sensors.
An electrical voltage with a varying direction is called alternating voltage. Periodic alternating voltage is a voltage, the variation of which is repeated in similar form at certain intervals.
If a coil is rotated at constant angular speed in a homogenous magnetic field, a sinusoidal supply voltage is induced. A one-phase system is achieved when the coil is connected to a loading circuit. If coils are placed on the surface of a rotor at random, and a separate loading circuit is connected to each coil, a multiphase system is achieved.
The multiphase system is symmetrical if all its supply voltages are equally high and if the phase angle difference between the supply voltages is equal; otherwise it is asymmetrical.
The most common symmetrical multiphase system is the three-phase system. Since the number of phases of the system is three, the angle difference between the phase coils of the generator is 120.degree.. As the positive direction of the supply voltages to be induced in phase coils we can select the direction from the end of the phase to its beginning. The phase sequence is then 1, 2, 3. If the rotor's direction of rotation is changed, the phase sequence becomes negative: 1, 3, 2.
By connecting three circuits together, the conductors can be partly shared by the different circuits. An electricity source for alternating current or an electrical apparatus to be connected to an electrical instrument is connected by joining either the beginnings or ends of the phase coils into a star point; similarly, in serial connection, the electrical apparatus is connected by joining the phase coils into a closed ring by always connecting the end of a phase coil to the beginning of the following phase coil.
At present, measuring the direction of rotation of a voltage in field conditions--when connecting electrical apparatus and installing new apparatus--is carried out galvanically on the live parts of a three-phase system, the measurement thus having to be done on bare conductor surfaces. The conductor insulation on the conductor surface has to be peeled off, and to the bare conductor surface is fastened a so-called alligator clamp or the like, which is connected to the measuring device through a conductor.
The disadvantages of the above known method are that the manner of measuring is not occupationally safe and carrying out the measurement alone in field conditions is difficult. In addition, the traditional measuring device must be connected when de-energized, that is, the supply of electricity must be disconnected for a moment.
The aim of the present invention is to eliminate the above-mentioned problems and to achieve a new method and measuring device which facilitate measurements in field conditions, and which are at the same time occupationally safe.
It is characteristic of the method relating to the invention that a measuring sensor operating on the electrostatic principle is mounted adjacent to each three-phase system wire, that the alternating voltage produced in the measuring sensors is transformed by means of an electronic coupling circuit or the like into rectangular pulses, that the pulse sequences obtained from all measuring sensors are transmitted to a logic circuit or microprocessor circuit which determines the direction of rotation on the basis of the phase difference between the pulses.
It is characteristic of the device relating to the invention that, after each measuring sensor a coupling circuit is connected, transforming the voltage produced in the measuring sensor into rectangular pulses, and that the coupling circuit outputs are connected to a common logic or microprocessor which determines the direction of rotation on the basis of the phase difference between the pulses.
By means of the invention a measuring device is achieved, with which t
REFERENCES:
patent: 1669159 (1928-05-01), Duncan, Jr. et al.
patent: 2128019 (1938-08-01), Sleeper
patent: 3825768 (1974-07-01), Grygera
patent: 3976919 (1976-08-01), Vandevier et al.
patent: 4028686 (1977-06-01), Wilson et al.
patent: 4710703 (1987-12-01), Harkiewicz et al.
patent: 4804922 (1989-02-01), Sometani et al.
patent: 4879509 (1989-11-01), Sometani et al.
patent: 5378979 (1995-01-01), Lombardi
Karlsen Ernest F.
Oy Sekko AB
LandOfFree
Method and device for indicating the direction of rotation of a does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and device for indicating the direction of rotation of a , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for indicating the direction of rotation of a will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-666093