How to ring a motor with a multimeter

Today we will discuss how to ring the electric motor with a multimeter. Able to use suitable screwdriver indicator. One caveat: having enlisted the help of a tester, we estimate the parameters, we distinguish the starting winding from the working one by the resistance value( in the first case the value will be twice as high).Screwdriver indicator miniature, convenient, the ability to use will acquire, if necessary, paying 30 rubles will find a new one.

The device electric motor

Varieties of engines abound. Made up of a moving part - the rotor - fixed - the stator. First of all, let's see where the copper wire is wound. Three answer options:

1. Coils only on the rotor.
2. Coils only on the stator.
3. On the movable and fixed part of the winding.

The rest of the asynchronous motor will ring out no more difficult than the collector. And vice versa. The difference is limited to the principle of action, without affecting the methodology for assessing the efficiency of the structure. In order to ring the electric motor correctly, stop analyzing the features.

Rotor of the electric motor

In this and the next subtitle we will teach how to ring a three-phase electric motor. If the coils( regardless of the number) are on the rotor, we look at the design of the current collector. There are at least two possible answers.

Graphite brushes

We see the rotor drum, equipped with pronounced sections. Current collectors are graphite brushes. The engine is collector. Need to ring all sections. The outputs of the coils are the opposite sections of the circle.

We take the tester, we begin to evaluate the resistance one by one: in each case the answer( in ohms) is the same plus or minus the error. When fixing a break, cleaning the drum does not help. The fact of infinite resistance or short circuit testifies: the coil burned out. In some engines, the coil resistance is close to zero.

Told what to do in this case. Take a normal Kron 12 volt, connect the rotor coil in series with low impedance( 20 Ohm).Using a tester, measure the voltage drop across the coil, the additional resistor, using the proportion, calculate the value( R1 / R2 = U1 / U2).Note: a high-precision resistor( E48 series or higher), so that the calculations have a small error. Can measure relatively small resistances.

Note: the current reaches 0.5 A at a power of 7 watts. Instead of a battery, it is better to take a computer power supply or a battery.

Continuous Rings

The current collector is made up of one or more continuous rings. Indicates eloquently: a synchronous motor( the number of phases by the number of sections), or asynchronous with a phase rotor. Actually, this does not matter, because they are going to ring the electric motor with a tester, determine the purpose of the device, we are too lazy. We look at the number of rings: the number fits within 1 - 3. The latter means: the motor is three-phase. We start to call.

The windings are connected by a star, as a result, the resistance between every two contacts is equal. If you have equipment to create a voltage of 500 V, you should ring the electric motor with a megger meter on the case. The standard insulation value is 20 MΩ.Please note: windings can not stand the test. With the engine at 12 volts such actions are not worth taking. As a result, with a fully serviceable rotor, you get equal resistance between the contacts. If a short circuit is detected on the case, check if it is a technical solution to create a system with a low-grounded neutral.

It is time to mention that for such a system the method of supply is characteristic for voltages below 1 kV.However, with resonant compensation( if it is possible to find an engine in nature) something similar can be used. By nameplate with marking, you can quickly resolve the issue( output neutral to the body).

Collector brushes are more often located perpendicular to the surface of the drum, whereas they are pressed against a current collector at a certain angle. The question arises - where is the neutral. Does not go to the case - do not use in the scheme. Often found at voltages above 3 kV.Here the neutral is isolated, the currents go through the phase, where in this case zero is present( or a negative value).

In high-voltage circuits, the common wire can be grounded through an arc suppression reactor. When a short circuit of one phase to the ground forms a parallel circuit between the capacitive resistance of the line and the inductance of the reactor. Actually, the type of impedance gave the name of the device( imaginary, reactive part of the resistance).At the industrial frequency, the resistance of the contour is close to infinity, as a result the break is blocked until the repair group arrives.

The rotor is often called the anchor.

The stator of the electric motor

After the rotor of the electric motor is cranked, work on the stator. Detail of a simpler design. If we are facing a generator, a part of the windings is exciting, in the general case one should simply find the resistance of each. The windings are starting only single-phase circuits. Coil resistance will be greater. Suppose there are three contacts, then the distribution between them is as follows:

• The common wire of both windings, to which zero( ground) is fed.
• Phase input of the working coil.
• End of the starting winding, where the voltage is 230 volts, bypassing the capacitor.

The difference is made by the magnitude of the resistance: between the phase inputs the nominal value is larger, therefore, the remaining end is the neutral wire. Further division is carried out as indicated above. The resistance of the starting coil is greatest( the difference between zero and this contact), the remaining ends will mark the working winding. The value of the active part of the impedance is reduced, reducing heat loss. Please note: on 230 volts there are also models of electric motors, where both windings are considered working. The difference in resistance between them is small( less than two times).

For three-phase motors, the stator windings are made on a different number of poles, always equivalent. Strict symmetry is confessed. Association is carried out according to the scheme of the star. In the high-power collector engines between the poles of the main coil can be placed additional( additional).Wound in one layer, therefore, demonstrate greater resistance. Designed to compensate for the reactive power of the armature. It is clear that the number of additional poles is equal to the number of main ones. The difference is limited by geometric dimensions.

The core of the additional poles is overlapped( laminated design) to reduce eddy currents. Similar to the rotor, a three-phase electric motor will not be sufficiently called by a multimeter, the insulation of the case should also be measured( typical value is 20 MΩ).

Additional constructive engines

Often the composition of the engines is replete with additional elements that optimize the work, perform a protective, different function. This should include varistors. Resistors connecting each brush to the body, with a sharp increase in voltage close the spark. Extinguishing is carried out. Phenomena such as a circular fire on the collector, lead to premature equipment failure.

The phenomenon is observed as a result of the occurrence of anti-EMF.The generation mechanism is quite simple: when the current changes in a conductor, a force is formed that counteracts the process. In the process of transition to the next section, the phenomenon causes the occurrence of a potential difference brush-non-working part of the collector. At voltages above 35 volts, the process causes ionization of the gap air, we observe in the form of a spark. At the same time, the noise characteristics of the equipment deteriorate.

This phenomenon, however, is used to track the constancy of the rotation speed of the collector motor. Sparking level is determined by the number of turns. When the parameter deviates from the nominal, the thyristor circuit changes the voltage cut-off angle to the desired direction in order to return the shaft speed to the nominal one. Such electronic circuit boards are often found in the composition of household food processors or meat grinders. The engine is as follows:

1. Thermal fuses. The response temperature is chosen to protect the insulation from burnout, destruction. The fuse is mounted on the motor housing with a steel handle, or hides under the winding insulation. In the latter case, the conclusions stick out, it is easy to ring a multimeter. It is easier to follow, with the help of a tester, an indicator screwdriver, on which connector feet the protection circuit goes. In the normal state, the thermal cutout gives a short circuit.
2. Instead of frequency fuses, temperature relays are installed. Normally open or closed. The latter type is used more often. They write a stamp on the case; you can find the corresponding type of element on the Internet. Then proceed according to the information found( type, resistance, response temperature, contact position at the initial moment of time).
3. Speed ​​sensors and tachometers are often installed on washing machine engines. In the first case there are three conclusions, in the second - two. The principle of operation of Hall sensors is based on the change in the potential difference in the transverse direction of the plate through which a weak electric current flows. Accordingly, the two extreme leads are used for power supply, should give a short circuit( small resistance), whereas the output can be checked only under the action of a magnetic field in the operating mode. To do this, apply power according to the electrical wiring. We recommend downloading the technical information( data sheet) to the Hall sensor present in the motor. Other options are invented. You can measure the power of the tester on the included washing machine. We believe readers understand the danger of manipulation. It would be better to remove the electric motor, apply power separately, only to the Hall sensor. Then it all depends on the design. If the magnet is permanent on the rotor, it is enough to simply rotate the axis with your hand so that pulses appear at the output of the Hall sensor( fixed by a tester).Otherwise, you will need to remove the sensor. Enlisting the help of a permanent magnet, checked performance. The Hall sensor in the composition of the electric motor is usually used to control the speed of rotation.

Now readers know how to ring a motor with a multimeter, the review ends. A number of specific devices can be continued indefinitely. The main thing is to ring the motor winding, the motor usually costs more than other parts. Do not take the case when the Hall sensor is priced at 4,000 rubles. Sure, readers will be able to supplement the recommendations. But enter the position - it is impossible to grasp the immensity. .. within the limits of one review.