Wattmeter

Power input to a three-phase machine may be measured by two single-phase wattmeters, connected as in the two-w attmeter method. (Section 11.4.3). Alternatively i single polyphase wattmeter may be used. 

The Power Factor is obtained by tbe ratio of the algebraic sum of wattmeter rettdings to voh-atnpere readings. For a three-phase system ... 

Generator protection. The generator proteetive relays are mounted in a switehboard, whieh usually houses the wattmeter and various transdueers, teleduetors, and optional watt-hour meters. 

A true RMS wattmeter for conveniently measuring efficiency and power factor. This is needed for off-line power supplies. 

Leistungs-fahigkeit, /. serviceability, power, ability productivity capacity (Meah.) efficiency, -faktor, m. (Elec.) power factor, leistungslos, a. (Elec.) wattless. Leistungsmesser, m. power meter (Elec.) wattmeter. 

Watt-messer, m. Elec.) wattmeter, -stunde, /. Elec.) watt-hour, -zahl, /. Elec.) num ber of watts, wattage. 

Electric Instruments, Many and various kinds of electric instruments are used in industrial processes and in analytical and research, laboratories, including those dealing with expls and ammunition. Among such instruments may be mentioned ammeters, voltmeters, galvanometers, thermocouples, ohm meters, wattmeters, frequency meters, oscillographs, computers, etc... 

This "circulating interface" is taken through the microcalorimeter (acting as a wattmeter), then to an oxygen electrode and is then returned to the microcosm (Fig. 1). 

Two-element wattmeter wired for three-phase, three-wire loads. 

Power measurements can be made in three-phase, four-wire circuits by a three-element wattmeter (Figure 3.55). Such a design is seldom utilized because the two-element wattmeter movement can be modified to permit measurement on three-phase, four-wire systems by reconnecting one of the fixed coils for each element. Meters of this type are known as 21/2-element wattmeters. They will correctly indicate power for three-phase, four-wire loads as long as the line-to-neutral voltages are balanced for all three phases. 

Digital wattmeters are available for both AC and DC applications for both single and multiphase measurements. Without using external components, the ranges can extend from a few milliwatts to tens of thousands of watts. Direct current wattmeters are the same as single-element AC wattmeters, but it is advisable to calibrate them for use on DC circuits. 

A Thomas flowmeter is a device in which heat is transferred at a measured rate from an electric coil to a flowing fluid, and the flow rate of the stream is calculated from the measured temperature increase of the fluid. Suppose a device of this sort is inserted in a stream of nitrogen, the current through the heating coil is adjusted until the wattmeter reads 1.25 kW, and the stream temperature goes from 30°C and 110 kPa before the heater to 34°C and 110 kPa after the heater. 

As viscosity builds further, a slight power increase will be noticed as the reaction moves into the transition region (B) where the mixing curve begins to bend upward. At a certain point, viscosity begins to build rapidly, and the reaction enters the viscous or laminar region (C). A rapid increase in power draw will be noted on the wattmeter if the motor is not greatly oversized. (A power draw of 35-50% of rated capacity at endpoint is usually sufficient.)... 

A wattmeter, however, automatically takes the phase angle into account and computes power directly. This provides an accurate measurement. Wattmeters are relatively inexpensive and can be installed by any electrician. Several measurement ranges (numbers of coils) can be built into one unit so that the same wattmeter can be used on pilot and plant-scale equipment. 

Find The endpoint of the reaction. Solution A wattmeter is used to correlate power draw to molecular weight (see the table) and the reading is then used to reliably determine the batch endpoint The reactor s mixing cur e (for one set of blades) is obtained from the vendor and is given in the figure. The initial Reynolds number ... 

Such a determination shows that, at the endpoint, the motor will not overload, and that the mixing is well into the laminar regime and the power draw is measurable. The first large-scale batch is successfully stopped at the proper molecular weight as determined by a wattmeter. 

A 40-cm-long, 0,4-cm-diameter electric resistance wire submerged in water is used to determine the convection beat liansfer coelQcient in water during boiling al I atm pressure. The suiface leinperaiuie of the wire is measured to be lld C when a wattmeter indicates the electric power consumption to be 7.6 kW. The heat transfer coefficient is... 

I - computer, 2 - condenser, 3 - exhaust system, 4 - vacuometer, 5 - manometer, 6 - thermal controlled box, 7 - thermostated liquid loop, 8 - cooling machine, 9 - power supply, 10 - wattmeter,... 

Compared to impeller torque, motor power consumption is easier to measure wattmeters are inexpensive and can be installed with almost no downtime. However, motor power signal may not be sensitive enough for specific products or processing conditions. Wear and tear of mixer and motor may cause power fluctuations. Moreover, power baseline may shift with load. 

Catalyst-circulation rate was originally measured by use of wattmeters or torquemeters connected to the bucket-elevator system (175, 185). The energy required to drive the elevator motors was calibrated against catalyst-circulation rate, as calculated from average bucket loading and number of buckets transported per hour. Later a radioactive-tracer method was developed that involves introducing a few radioactive particles into the catalyst inventory and determining the time required for each of these particles to pass from one end of the reactor seal leg to... 

The power is measured by the cathode-ray wattmeter method. Let the deflecting sensibility of each pair of deflection plates be Di and D2, respectively Ci is the capacity of the current calculating condenser, which is inserted in place of the resistance, R, to measure the current. Then the area of the diagram, A, is given by... 

On an over-all basis the average, computed from the main wattmeter of the plant and including all losses, is 39 watt-hours per gram of ozone available for water treatment (equivalent to 17.7 kw.-hr. per pound of ozone). 

Wl and W2 can easily be measured with a wattmeter or with an oscilloscope by determining the applied voltage (V), the current intensity (/) and the phase shift (cos <(>). Determination of the phase shift at the entry of the transducer may provide interesting information [25,26]. However the determination of these quantities is very seldom reported in patents or research papers. 

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