Fundamentals of Smart Metering - kWh and kVArh Meters
The kilovolt-amperes (kVa) are the generator end capacity. Generator sets are usually shown with both ratings. To determine the kW and kVa ratio the formula. The unit used for contract demand is kVA or kW. .. Test connection diagrams, shown in the figure below shows methods of connecting. Originally Answered: Why are transformers rated in kVA and not in kW? .. but it is not always possible to predict the phase relationship (power factor) between.
Power Calculator for Generators: Convert kVA to kW, kW to kVA, kW to HP
This causes eddy currents to be set up in the disk. The reaction between the eddy currents and the field tends to move the disk in the direction of the field. While on load, the disk revolves continuously. This induces the emf electromagnetic force in it dynamically, as it cuts through the flux between the poles, in addition to the statically induced emfs due to the alternating flux in these poles. Torque is produced due to dynamically induced eddy currents in the disk.
This torque is negligible as compared to the operating torque produced by the statically induced currents. Tr is the retarding torque due to eddy currents in proportional to the speed of revolution, N, of the disk, i. In order to achieve steady state speed of the disk, Td must be equal to Tr; hence we can write This means that the speed of revolution of the disk is proportional to the power.
The total number of revolutions, NT, over a time interval T is given as: This equation shows that the total number of revolutions is proportional to the total energy supplied. Poly Phase Induction Watt-Hour Meter Polyphase energy can be measure by several single phase circuits that make up the polyphase circuit. The energy delivered over a polyphase circuit is the total energy delivered over each equivalent single-phase circuit. Polyphase energy can be measured by connecting a single-phase watt-hour meter in each phase and then adding up readings of individual meters.
This is not commercially practicable because: The electrical industry has developed polyphase watt-hour meters. The polyphase watt-hour meter is a combination of single-phase watt-hour meter stators that drive a rotor at a speed proportional to the total power in the circuit. The meter consists of a multi-stator motor, means for balancing the torques of all stators, a magnetic retarding system, a register, and compensating devices.
These components are assembled on a frame and mounted on a base.
The operating principle of polyphase watt-hour meters, having any number of stators, is the same as single-phase watt-hour meters. Torque on each stator results from current in one set of electromagnetic coils and eddy currents induced in a disk, or disks, by current in the other set of coils.
The torques of the several stators combines to give a resultant torque proportional to total power. Because the same rules apply to measurement of both polyphase energy and polyphase power, principal parts of single-phase watt-hour meters can be combined for polyphase energy measurement, much as components of single-phase watt-meters are combined for polyphase power measurement.
Blondel's theorem applies to measurement of energy exactly as it does to measurement of power. A polyphase watt-hour meter is built with the number of elements necessary to satisfy Blondel's theorem. Hill-Schotter kVArh meter The spherical integrator types of kVArh meter The Landis and Gyr trivector meter Hill-Schotter kVArh meter This meter is essentially an induction type ampere hour meter with the registration mechanism designed for a particular system voltage.
The system undergoes some voltage variation, to compensate for which a voltage compensating device is added to the system. Principle of operation The main driving magnet M is a shaded pole electromagnet. This electromagnet is supplied by the load current.
The electromagnet V is energized by the system voltage. The armature A is attached to spindle S switch carries two control weights W1 and W2, the balance weight W3 and the copper shading piece P. The movement of P is prevented by the control weight W2 until the system voltage exceeds the predetermined value. Weight W1 prevents its movement until the system voltage comes down the predetermined value.
The effect of the shading piece P is to increase or decrease the driving torque according to whether the voltage is high or low.
The breaking torque is developed due to a permanent magnet together with the main electromagnet. Spherical Integrator type kVArh meter This is an integrator type of meter because it essentially consists of both kWh and kVArh meters together with a mechanical device called spherical integrator. To expand on it a bit more, the kW rating is essentially the resulting power output a generator can supply based on the horsepower of an engine.
For example if you have a horsepower engine it has a kW rating of The kilovolt-amperes kVa are the generator end capacity.
How to convert VA to Watts and KVA to Kilowatts
Generator sets are usually shown with both ratings. To determine the kW and kVa ratio the formula below is used. The power factor pf is typically defined as the ratio between kilowatts kW and kilovolt amps kVa that is drawn from an electrical load, as was discussed in the question above in more detail.
It is determined by the generators connected load. The pf on the nameplate of a generator relates the kVa to the kW rating see formula above.
Generators with higher power factors more efficiently transfer energy to the connected load, while generators with a lower power factor are not as efficient and result in increased power costs.
POWER ELECTRICS BLOG
The standard power factor for a three phase generator is. What is the difference between standby, continuous, and prime power ratings?
Standby power generators are most often used in emergency situations, such as during a power outage. It is ideal for applications that have another reliable continuous power source like utility power. Continuous power is similar to prime power but has a base load rating. It can supply power continuously to a constant load, but does not have the ability to handle overload conditions or work as well with variable loads.
Generator FAQ - Frequently Asked Questions about Generators | Diesel Service
If I am interested in a generator that is not the voltage I need, can the voltage be changed? Generator ends are designed to be either reconnectable or non-reconnectable. If a generator is listed as reconnectable the voltage can be changed, consequently if it is non-reconnectable the voltage is not changeable.
What does an Automatic Transfer Switch do? An automatic transfer switch ATS transfers power from a standard source, like utility, to emergency power, such as a generator, when the standard source fails. An ATS senses the power interruption on the line and in turn signals the engine panel to start.