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A phase meter is a device used to obtain accurate information about the magnitude of the phase shift between two electrical oscillations that change from time to time. The device is usually used for measurements in a 3-phase network.
Phase meters are often used in electrical installations to calculate the reactive power factor (cosine “phi”). The device is actively used in the operation of electrical substations and networks, in the development of electronic and electrical products.
Briefly about the phase meter
To carry out measurements, the phase meter is connected to the voltage circuits, which act as a reference point, and the current circuit, which shows the position of the measured vector. When working in a 3-phase network, it may be necessary to connect to all phases.
The peculiarity of modern devices lies in the simplified principle of application, therefore, it will not be difficult even for an inexperienced specialist to deal with the features and subtleties of using a phase meter.
The measurement is made for two phases, after which the last phase is calculated based on the addition of vectors. In addition, the phase meter is often used to measure the cosine “phi”, as mentioned at the beginning of the article.
Types
All phase meters according to the principle of operation are divided into three types:
- Electrodynamic;
- Digital;
- Electromechanical.
The first two types are in the greatest demand, but it is recommended to use digital devices. They are characterized by greater accuracy and low interference.
According to the number of phases, phase meters are:
- Single-phase – for measurements in a 1-phase circuit.
- Three-phase – for 3-phase circuits.
Electrodynamic
Until recently, electrodynamic (electromagnetic) phase meters were in the greatest demand. Structurally, this device consists of a simple ratiometric mechanism that allows you to accurately measure the phase shift.
The device has two frames that are rigidly connected to each other. The angle between the mentioned elements is 60 degrees. The frames are mounted on axes fixed on the support nodes. Due to this feature, there is no mechanical resistance in the device.
The device has a special element that rotates through an angle that characterizes the magnitude of the current phase shift. Using a linear scale, a specialist can fix the measurement and determine the current displacement parameter.
The electrodynamic phase meter is based on a fixed current coil, as well as two more similar, but moving elements. In the displaced coils, currents flow, which contributes to the appearance of a magnetic flux in all coils – movable and stationary.
When the coil flows interact, a pair of rotating moments appears, the magnitude of which depends on the distance between the moving elements of the device. The mentioned moments have a different direction, which is opposite in magnitude.
The torque values depend on the currents flowing in the moving coils, as well as on the current level in the fixed coil. In addition, the mentioned indicators depend on the design features of the coil and the angular phase shift.
As a result, the moving element of the phase meter scrolls under the influence of the mentioned moments until the situation when equilibrium does not occur, that is, the moments become equal.
The phase meter itself often has a graduation that allows you to accurately measure the power factor.
The advantages of the device are reliability, high accuracy of readings, affordable price.
The disadvantage is the dependence of the measured parameters on the frequency indicator. Another disadvantage is the increased power consumption from the source under study.
See also:
Digital
As noted, this is a more preferred type of instrument due to more convenient use and high accuracy. Such devices are manufactured using various technologies.
For example, a compensation phase meter makes the most accurate measurements, despite the need for manual use. The device works on a different principle. During the measurement process, a pair of U appears, having a sinusoidal type, and the main purpose of the device is precisely to calculate the shift between the phases.
First, U is fed to the phase shifter, which is controlled from a special device. The measurement process proceeds smoothly until the phase coincidence occurs. During tuning, the amount of phase shift is calculated using a phase-sensitive device.
The output signal is transmitted from the detector to the control device. The specified algorithm is implemented by means of pulse coding. Once balancing occurs, the phase shifter code reflects the information of interest.
At the present stage, digital phase meters use a technique based on a discrete count. The essence of the method is the passage of two stages.
First, a process is performed to convert the phase offset into a signal parameter with a certain duration. Further, the length of this pulse is changed using a discrete count.
The device includes:
- A converter that provides the conversion of phase displacement into an impulse;
- Time selector;
- An element that generates discrete pulses;
- Control device and counter.
The advantages of digital-type phase meters are a smaller error due to calculations over several periods, greater accuracy and ease of use. Disadvantages – higher price.
See also:
User’s manual
To understand the use of the phase meter, the main attention is paid to the instruction manual (included with the device). Before you get started, there are a few steps you need to take.
To begin with, it is worth making sure that the operating conditions correspond to those recommended by the manufacturer, and the frequency range is in accordance with the metrological characteristics. After that, the circuit itself is assembled.
The operation of the phase meter is performed according to the following algorithm:
- First you need to read the instructions that come with the product. The document reveals the nuances and rules for using the device.
- With the help of the corrector, the arrow is set at the 0th mark.
- Make sure the buttons don’t work.
- Connect the input probes to the required sockets.
- Press the key that supplies power to the device. Pay attention to the fire of a special indicator.
- Wait a while for the appliance to warm up well. This is necessary to achieve maximum measurement accuracy. On average, the exposure time should be about 10-15 minutes.
- Find the input voltage.
- Press the key depending on the choice of external voltage and set the required frequency range.
- Press “>0
- Connect the channel probes to the 4-pole input.
- Set the border switch to position “20”.
- After the meter arrow, use the regulator to set the “zero” position.
Popular models on the market
Consider several models of phase meters that are in the greatest demand today.
Phase meters D5721 and D5782
They are used to work in 1-phase AC circuits with a frequency of 50 (60) Hertz and allow you to measure the phase shift between the harmonic components of current and voltage.
The device has a high accuracy class (0,5), allows you to measure angles in the range from 0 to 360 degrees. The weight of the device is not more than 6,5 kg, and the dimensions are 23 * 28 * 14 cm.
Megeon 40850
This model of the phase indicator belongs to the category of portable (compact) devices that allow you to perform measurements with high speed and accuracy.
To diagnose the correct phase sequence or the presence of errors, the LEDs installed on the front panel are used. There is also a built-in buzzer.
The advantages of Megeon 490850 is its readiness for work and compliance with the 2nd security class. In the process of measurement, “crocodiles” are used (included in the kit), which simplifies the process of using the device.
The package includes the device itself, crocodile clips (3 pcs.), wrist strap (3 pcs.), instruction manual, as well as a case for storing and transporting the device.
The gross weight of the product is only 810 grams, and the dimensions of the box are 15 * 10 * 15 cm. The device measures at a voltage of 200 to 400 V. Protection level IP65. Optimum working temperature from -10 to +40 degrees Celsius.
Ts302 – three-phase phase meter
The main purpose of the Ts302 phase meter is that it can be used to quickly and accurately measure the “phi” coefficient in a variable network. The frequency of the current can be different – from 50 to 10 thousand Hz. The dimensions of the device are 12*12*9,5 cm, the accuracy class is 2,5.
The model under consideration is characterized by increased resistance to shock and vibration. The principle of operation of the meter is based on the conversion of the input sinusoidal signal into rectangular pulses, followed by conversion to direct current.
The parameter I depends on the angle of the phase shift. The Ts302 includes an electrical meter and an indicator of the magnetoelectric system.
See also:
Phasometer E35000
The task of this equipment is to verify the correct operation of the D578 and D5782 phase meters.
In addition, the product is used for measurements in various circuits with a high accuracy class of 0,2 (in case of application without a transformer).
The operation of the product is based on comparing the obtained angle of difference between the initial parameters of the voltage and current distortion phases with a given indicator. The error of the model is up to 0,1%. Dimensions – 23 * 28 * 14 cm. Weight 7 kg.
Phasometer D5000
Model D5000 is used to determine the accuracy of single-phase phase meters operating at a frequency of 50 Hz. This type of measuring device is often mounted in circuits with separated current and voltage circuits.
The rated current and voltage of the device are 5 and 10 A, as well as 100, 127 and 220 V, respectively. Power consumption in series / parallel connection 5 and 8 Amps, respectively. Outwardly similar to the previous device.
Single-phase phase meter S302-M1
Model C302-M1 is used to measure the power factor in a 3-phase AC network having a frequency of 50 Hz. The main condition is the symmetry of the line voltages, as well as the symmetry of the load of the phases.
Structurally, the device consists of an electronic type converter, as well as an indicator of the magnetoelectric system (both elements are in the same housing).
Phasometer C42305
The model of the phase measuring device Ts42305 is used to measure the power factor in 3-phase networks with a nominal frequency of 50 Hz under the condition of a symmetrical load and the presence of linear U symmetry.
The device is based on an electronic device that converts the input signal, as well as a magnetoelectric element.
The accuracy class of the model is 2,5. Rated voltage (220, 100, 380 or 127 V). The connection is made directly via a CT or VT.
Phasometer C42309
The Ts42309 meter is used to calculate the exact power factor in 3-phase AC networks. The principle of operation is based on the operation of an electronic type converter, which receives input signals and converts them to direct current.
The accuracy class of the instrument is 2,5. Rated voltages – 220, 100, 380 or 127 V.
Other models
In addition to the phase meters discussed above, it is worth highlighting a number of models – phase meters PIC144A, FTZ144 500V, FEMC144 110V, FEMC96 100/v3, FEMC96 100V FTZ96 230V, FEMC96 100V and others.
The importance of phase meters is difficult to overestimate. With the help of this device, it is possible to accurately measure the coefficient “phi”. This parameter indicates the presence of a reactive component in the network.
Based on the measurement results, specialists decide on the need for power factor correction and the general nature of the load.