A three phase watt meter's potential transformer and current transformer are located remotely from the metering cabinet. On large size bus installations it would be impossible to take the bus bars to the meter so it is done the other way around. Leave the Ct's and Pt's on the bus bars and use smaller wire to feed the meter in a remote accessible location. The utility company requires a metering cabinet over certain voltages and amperage be accessible to the meter reader. In some installations the metering cabinet is installed remotely on the outside of the building away from the electrical room.
There are two alternate methods depending on whether the motor is single phase or three phase. On a single phase motor, reverse either the start winding coil lead or the run winding coil lead but not both. This action will reverse the motor's rotation. On a three phase motor, interchanging any two of the three coil leads will reverse the motor's rotation.
The order in which the voltage of the coil reaches to the maximum value is called the Phase Sequence.POSITIVE PHASE SEQUENCE: If the coil is rotated in anticlockwise direction, the phase sequence will be Positive Phase Sequence, i.e., R-Y-B or A-B-C.NEGATIVE PHASE SEQUENCE: If the coil is rotated in clockwise direction, the phase sequence is called Negative Phase Sequence, i.e., R-B-Y or A-C-B.NOTE: Phase Sequence is of great importance in parallel operation of three phase transformers and alternators.
There are two coils in watt meter namely current coil & potential coil.the two ends of current coil are 'M' & 'L' and they should connect in series with instrument. and the two ends of p.c. is 'c' which is connected to 'L'. and another is at the other end of instrument.There are two coils in watt meter namely current coil & potential coil.the two ends of current coil are 'M' & 'L' and they should connect in series with instrument. and the two ends of p.c. is 'c' which is connected to 'L'. and another is at the other end of instrument.There are two coils in watt meter namely current coil & potential coil.the two ends of current coil are 'M' & 'L' and they should connect in series with instrument. and the two ends of p.c. is 'c' which is connected to 'L'. and another is at the other end of instrument.
Two wattmeter method is used in a three phase sysstem to measure the true power without regard to the balance ie. It can be used to measure both balanced loads and unbalanced loads.The three phase power could be measured using single phase wattmeters in each loads of the system. But using three wattmeters is quite unnecessary as we can measure it by using only two wattmeters.The three phase power could be measued by using single phase wattmeters , haing a current coil in one line and a potential coil connected between the line and some arbitrary common junction point. If that arbitrary common point is chosen on one of the three lines, then the wattmeter connected to that line will indicate zero power because it's potential coil has no voltage across it. hence, that wattmeter may be eliminated, and the three phase power can be determined by means of only two single phase wattmeters.
one windingAnswerA three-phase motor has three phase windings, normally (but not necessarily) connected in delta.
your not completing the circuit your only using one phase for a three phase motor
There are two alternate methods depending on whether the motor is single phase or three phase. On a single phase motor, reverse either the start winding coil lead or the run winding coil lead but not both. This action will reverse the motor's rotation. On a three phase motor, interchanging any two of the three coil leads will reverse the motor's rotation.
The two-wattmeter method can be used to measure power in a three-phase system. Each current coil is connected in series with one of the live phase wires, while the voltage coils are connected between those and the third live wire.
Three coils ( Suppose: A, B and C ) are placed at 120 degree from each other in uniform magnetic field. The coils are rotated at uniform angular speed ( Suppose: omega ) ( unit: radian per second ). Emfs are induced in each coil. As coil B is placed at 120 degree from coil A, emf induced in coil B lags behind that of A by 120 degree. If the three phase voltage are equal in magnitude, the sum of the three phase voltage is zero. This can be shown by different ways. ( e.g. Vector sum ). The order in which the voltage of the coil reaches to the maximum value is called the phase sequence. ( Phase sequence is of great importance in parallel operation of three phase transformers and alternators ). Phase sequence R-Y-B is known as the positive sequence, while R-B-Y is known as the negative sequence. Phase sequence can be checked by using phase sequence indicator. Phase sequence can be reversed by interchanging any two terminals.
A three-phase motor has a steady rotating magnetic field generated by the stator coil, and the rotor just follows the field.
15 a ig coil meter
The terms you are looking for are 'dynamometer' (no hyphen!) or 'electrodynamic' instrument. These terms describe an instrument movement, where the torque applied to the pointer results from the interaction of magnetic fields produced by fixed and moving coils. In the case of a wattmeter, the fixed coil is the current coil which is connected in series with the load, and the moving coil is the voltage coil which is connected in parallel with the load.A dynamometer type instrument differs from a moving-coil instrument, such as an ammeter or a voltmeter, in which the torque applied to the pointer is the result of the interaction between the magnetic fields produced by the moving coil and a permanent magnet.For three-phase power measurements, it is possible to use just two wattmeters in a configuration called the 'two wattmeter method'.
The order in which the voltage of the coil reaches to the maximum value is called the Phase Sequence.POSITIVE PHASE SEQUENCE: If the coil is rotated in anticlockwise direction, the phase sequence will be Positive Phase Sequence, i.e., R-Y-B or A-B-C.NEGATIVE PHASE SEQUENCE: If the coil is rotated in clockwise direction, the phase sequence is called Negative Phase Sequence, i.e., R-B-Y or A-C-B.NOTE: Phase Sequence is of great importance in parallel operation of three phase transformers and alternators.
interchange connections of c and v i.e pressure coil
for what or in what?
There are two coils in watt meter namely current coil & potential coil.the two ends of current coil are 'M' & 'L' and they should connect in series with instrument. and the two ends of p.c. is 'c' which is connected to 'L'. and another is at the other end of instrument.There are two coils in watt meter namely current coil & potential coil.the two ends of current coil are 'M' & 'L' and they should connect in series with instrument. and the two ends of p.c. is 'c' which is connected to 'L'. and another is at the other end of instrument.There are two coils in watt meter namely current coil & potential coil.the two ends of current coil are 'M' & 'L' and they should connect in series with instrument. and the two ends of p.c. is 'c' which is connected to 'L'. and another is at the other end of instrument.
Two wattmeter method is used in a three phase sysstem to measure the true power without regard to the balance ie. It can be used to measure both balanced loads and unbalanced loads.The three phase power could be measured using single phase wattmeters in each loads of the system. But using three wattmeters is quite unnecessary as we can measure it by using only two wattmeters.The three phase power could be measued by using single phase wattmeters , haing a current coil in one line and a potential coil connected between the line and some arbitrary common junction point. If that arbitrary common point is chosen on one of the three lines, then the wattmeter connected to that line will indicate zero power because it's potential coil has no voltage across it. hence, that wattmeter may be eliminated, and the three phase power can be determined by means of only two single phase wattmeters.