in the form of generators are often used asynchronous motors. This is due to the presence of the shaft remanence. Drum under squirrel cage molded from a lightweight alloy axis represents pure ferromagnetic material. As a result, after a stop, the motor shaft is often left magnetized. Below we explain how to verify generator multimeter describe the methods starting the engine, achieving of electric current.
Most modern electric power generators operate on the basis of Faraday's law for EMF stating that the conductor a voltage proportional to the area and rate of change magnetic flux. In addition, said value is multiplied by the number of turns. Immediately see ways to increase the voltage:
- Increase the area of the coil winding.
- Increase rate of magnetic flux change:
- By increasing the excitation current of the rotor or more strong permanent magnets.
- By increasing the rotational speed.
If we take the industrial generators, preferably the first method is used. This is due to stringent requirements for frequency generation. As for the coil area, the parameter is set constructive change is problematic. The purpose of describing simple facts: many examples found in the network, where the motors are trying to run as generators. Some attempts are not successful, and the authors demonstrate ignorance simplest laws of physics.
Thus, the advantage of synchronous generators in the frequency constant - often this is the main requirement. From voltage parameters are directly dependent on engine speed, normal operation and other filter circuits. If the voltage is wrong, first of all, you want to check the generator voltage regulator comparison with the testimony of a multimeter. Imagine now what would happen if the power frequency will increase twice. Yes, certain types of asynchronous squirrel-cage motors, in addition to collecting react predominantly amplitude. So what is next?
- Checking voltage generator multimeter rate difference output potentials (major) nests (terminals), not including ground line.
- Checking charging generator, perform measurement on the DC nest 12 V.
Are invited to choose the right equipment for the power supply. And in the case described this knowledge is important for the reason that the design of synchronous and asynchronous generators are different. Consequently, the test methods are required to take into account the mentioned fact. A brief look at types of alternating current generators.
Various designs of generators
Said induction generators are called for that the generated AC frequency is different from the rotational speed (even taking into account the number of poles). Structurally similar machine is considered to be a typical engine with a phase or a magnetized rotor. From synchronous winding shaft by the absence of the area between the poles. Due to this, the plus and minus less pronounced. Thus, depending on the design type induction motor start technique in its generator mode differs.
For pre-cage rotor relies magnetize the shaft. This is done by a short but high current pulse. The polarity of the poles depends on the location. Please note that a relatively small section of the shaft does not allow to create a strong magnetic field. Hence, according to the above, we conclude that a large voltage will not be able to receive using the described generator. Much more advantageous to magnetize the rotor phase of the plates by applying a voltage to the coil. With the stator voltage will begin to appear. The driving force becomes:
- Combusted gases, or the car engine shaft.
Electricity is produced by changing the pitch. The magnets are permanent (short-circuited rotor) or electrical (rotor phase). The second type of device is needed to supply the current, for example, from the battery through the current collector (ring shaft). Consistent with this construction methods loom check generator multimeters. In the case of a squirrel-cage rotor stator solely testing. Number of outputs depends on the phase character of the power and other features:
Generator asynchronous type
- Three-phase stator winding of the generator integrated in star. Form a common point and three opposing end planted into phases A, B and C. In this case, the pairs should multimeter to check the generator for the resistance value. The answer is always the same.
- Then he checked the insulation on the body. This will require special equipment: driver test voltage of 500 V and a current clamp (one option among others). Insulation resistance standard is not less than 20 megohms. If there is a short circuit, the motor is constructed according to the scheme with gluhozazemlonnoy neutral, which is typical for voltages up to 1 kV. In this case, the structure is specified by the specifications. Easier data on the induction motor on the Internet.
- Domestic induction motor stator much more complex. Such machines are not used as generators, but... we'll show you how to check performance. In most cases there are two windings, one is fed via the capacitor, and becomes the starting or auxiliary. In our case, each allowed to take power. The resistance of the auxiliary (or launcher) windings are generally slightly larger than that of the working. It's easy to check the tester. Then he measured the insulation resistance in the generator housing.
The rotor is tested with the current collector. Three-phase circuit are designed to work with isolated neutral, to ensure the winding of the generator multimeter to measure resistance should pairwise between all three rings. Values are required to catch up. Sometimes there is a short to the housing (with gluhozazemlonnoy neutral scheme). All abuts the structural features of engines (generators). If you have one or two rings to draw conclusions about single-phase supply. Nicknamed the coil, check the insulation housing.
Synchronous generators operate in a similar manner, but is held constant shaft speed. Hence, the parameters are more stable. Here are a number of differences are taken into account in order to properly check the generator multimeter.
On the stator (referred to as an anchor) is often present AC coil, synchronizing the rotation. Its role is hard to overestimate, and the coils are, for example, between the main coil windings. The role of the poles in this case, the sync. This voltage is connected to the desired frequency, due to the interaction with the inducer (rotor) specifying the rotational speed. Typically the winding dimensions are smaller than the main higher resistance.
In large synchronous generators present accessories - podvozbuditel. This synchronous machine, the shaft of which is equipped with permanent magnets. Voltage generated by the generator is rectified and is then used as a current for the exciter. So energy is saved. The permanent magnets in addition, reduce the number of current collectors, which positively affects the reliability of the entire system. Podvozbuditel becomes, in fact, a simple synchronous motor type, the stator winding prozvanivatsya tester in the normal way.
In connection with the above, sometimes you want to check a diode bridge multimeter generator. By the way, it is important for motorists, which is often used for the rectification of Larionov circuit. Diode bridge prozvanivatsya depending on the design. The most common domestic shown. First it considered typical solution for single phase alternating current, and the second - a diagram Larionov.
According to the resulted figure show how to ring. The single-phase diode bridge safely evaluated the integrity of each diode individually. For this purpose, the corresponding mode is set multimeter Further, regardless of the position of cathode and anode, the probes are represented with one side and then the other. As a result, direct incorporation gives a value of 500 - 700 ohms, and the reverse - breakage.
Popular designs diode bridges
The result is different if somewhere in the chain of resistors shorted bridge, but this happens rarely, and their face value is large enough to have no effect. Road bridge Larionov prozvanivatsya similarly. If possible, remove it from under the hood. Login each phase calls to the positive and negative output. Resistance Value - to 1 kOhm. The reverse inclusion is easy to check. It is believed the red probe to positive supply and in turn make sure that all the phases to give the black probe infinite resistance. Similarly verified mass. Here the black test lead on the negative output goes, and red - in phases.
AC generators as motors, are often equipped with thermal fuses, tachometers Hall sensors and other accessories. There are specific steps, for example, generator protection relay asynchronous mode (that is fraught with equipment failure). In general, keep in mind that ordinary engines often run in a specific mode. Therefore, it is required to be able to maximally simple way to test accessories:
- Thermal Cutoffs are calculated at a certain temperature, usually indicated on the package. When exceeding some threshold melted insulation that is fraught with windings of malfunction. If you take the generators, they overload fenced using MTP (relay overcurrent) that sochtom analogue fuse. The action is based on the limitation of capacity, requested by the consumer. For example, the short-circuit of one phase is simply terminates. Regarding Thermal Cutoff typical engines, their location is usually limited to the surface of the magnetic circuit or insulation of the windings (hump clearly visible among turns). It is necessary to find the output terminals and the circuit to ring from the socket.
- Thermal Thermal Cutoff considered analogues with a reusable actuation, saves winding of combustion. When the engine cools down, the current generation can be resumed.
- frequency sensors are usually built on the principle of tachometers. Organization of different devices, depending on the wire and check.
To summarize, each engine may run as a generator. This is clearly written in the Wikipedia. Be that as it may, the design of the generator reveals features. Specific methods for regulation and protection are different from those used for engines. Impose restrictions stopping results: in the case of failure of the generator is much more sad consequences. Already because of the presence of such features the price is very different.
In summary: according to unconfirmed data have asynchronous generators less vulnerability to short circuit on the load side, and the voltage waveform better. In addition, eliminating the need for maintaining the rotational speed, which would be a big plus for practitioners. Regarding the organization of HPP, they apply only synchronous machines due to obviousness standards.