Electric clamps are focused on measuring the relevant characteristics (phase angle, voltage, power, current, etc.). In this case, the working circuit is not broken and its functioning is not disturbed. There are voltmeters, ammeters, phase meters and clamp-on wattmeters.
General information
Among the considered type of tools, the most widely used are electric clamps for measuring current (AC ammeters). Their main purpose is the operational measurement of the corresponding value in the conductor element, without interrupting its working state. These devices are used in systems up to 10 kilowatts.
Elementary electrical clamps for alternating current operate according to the transformer principle, with one turn and a primary busbar winding. The secondary layer is a multi-turn analogue placed on a detachable magnetic wire to which an ammeter is connected.
Working principle
To check the tire, the magnetic wire of the electricalpliers opens under the force of the worker, who compresses the insulating handles of the tool. The alternating current passing through the line in the part of the coverage transfers to the magnetic circuit the working flux induced by the electromotive force in the winding of the secondary configuration. A current is created in its closed space, its indicator is measured by an ammeter.
In modern modifications of the considered devices, a circuit is used in which a rectifier and a current transformer are combined. This design provides for connecting the outputs of the "secondary" using a set of shunts.
Types
Electrical clamp meters are divided into two types:
- Single handle models for installations up to 1 kW.
- Analogues with a pair of handles for systems from 2 to 10 kW.
In the first modifications, the insulating compartment is also a handle. The wire-magnet opens with a push-on configuration lever. For two-handed versions, the insulating part is at least 380 millimeters long, and the handles are from 130 mm. The first group has no control dimensions.
The device under consideration consists of three blocks:
- Working element with magnetic circuit, winding and meter.
- Insulating part.
- Pens.
Application
Electric clamps are also used in closed installations or open systems (if it is dry outside). Measurement work is allowed to be carried out onon insulated parts (cables, wires, fuse holders) and exposed parts (e.g. busbars).
The operator working with the tool must wear dielectric gloves while standing on an insulating mat. His assistant is located slightly behind and to the side, reading information from the instruments.
Modification C-20
Crimping electric pliers of C-20 configuration are equipped with an open-type magnetic circuit and a rectifier system. This device belongs to the transformer current group. Ts-20 clamps make it possible to measure a value in the range from 0 to 600 A. In this case, coverage is performed on a wire element, alternating current in frequency does not exceed 50 Hz.
In this modification, the "primary" is the current conductor itself, provoking a variable value in the closed space of the ferromagnet, transmitted to the secondary winding using the EMF, where the electrical measuring apparatus is connected.
The read current is directly proportional to the value in the tested conductor. Its reading is carried out on a dividing scale from 0 to 15 (if the switch lever is in position 15, 30, 75 A). Otherwise, the measurement is carried out according to the lower ruler (from 0 to 300).
If you connect the clamps of the C-20 device with conductors to the points of the electrical circuit between which voltage is monitored, then you can track the parameter of alternating voltage up to 600 volts at a frequency of 50 Hz. In this case, the switch-lever is moved to the "600 V" position when"secondary" transformer shorted.
Electric press tongs D-90
The design of this device includes a sliding magnetic circuit with a ferromagnetic part and a dynamic device. Product features allow you to read the active power characteristic without breaking the current circuit. The process itself is carried out by covering the conductor and connecting a couple more analogues with plugs to the mains.
Actual voltage and current measured by D-90:
- 220 and 380V;
- 50Hz;
- 150, 300, 500A;
- 25, 50, 75, 100, 150 kW.
Calculations for measurements in the norm 25-100 kW are carried out on the upper scale, the gradation of which is from 0 to 50, and from 75 to 150 kW the gradation is from 0 to 150. The parameters are switched by plugs. One of them is placed in a special generator socket marked "", the second - in a 220 or 380 V socket.
Correction of limiting current measurements is carried out with the help of a lever-switch, which is translated into one of six positions, identical to the nominal values of voltage and active power under investigation. The device in question is allowed to control a similar parameter in circuits with three phases. To do this, a linear wire is covered by a magnetic circuit. In this case, the voltage winding is connected to the required phase or line.
In symmetrical modes, you just need to take into account the power indicator of one phase, followed by its triple multiplication. ATotherwise (asymmetric), the corresponding powers are checked in turn, according to the data of two or three instrument circuits. The resulting numbers are added in algebraic order. It should be noted that the error parameter when using Ts-20 and D-90 does not exceed 4% of the available limit with different placement of teeth and conductor in the part of the magnetic wire.
How to use electric pliers correctly?
To get started, do the following:
- The required range is set on the switch.
- Activate the magnetic wire release key.
- The working elements are wrapped around the conductor on alternating or direct current, depending on the type of device.
- Place the pliers perpendicular to the direction of the wire.
- Retrieve data from the monitor.
Sometimes the difficulty of operating the device is associated with the selection of a single conductor. An attempt to take readings from a conventional cable that comes from an outlet should be accompanied by zero on the monitor. This action occurs for the reason that the phase and zero currents of the conductor are identical in magnitude and opposite in direction. Given this feature, the generated magnetic fluxes are mutually leveled.
In the case of non-zero current readings, there is current leakage in the circuit. Its parameter will be equal to the received value. In this regard, it is necessary for measurements to find the place of separation of the wires, followed by the allocation of one core. Suchthe point can be a switchboard or a place where a phase is connected to a circuit breaker. This option is not always possible, which narrows the scope of electric tongs.
If during the measurement work the unit is visible on the display, this means that the parameter of the current strength in the wire is beyond the limit of the measurement range. In this option, you will need to increase the range using the switch. To work in hard-to-reach places, it is recommended to use the Hold key. It will allow you to fix the latest information, which will remain even after removing the tool. Pressing the button again resets the stored data.
Safety measures
How to use electric pliers, described above. In addition to the above safety measures regarding the uniform of the operator, several other factors should be considered. If the instrument is used intensively, it should be checked at least twice a year. When purchasing a tool for home use, you should pay attention to the date of verification by the manufacturer, which is available on a special stamp. It is recommended to work with a team of two people: one of them takes the parameters, and the other writes down the obtained values.
