Check and repair of asynchronous electric motors. Measuring the insulation resistance of an electric motor What is the resistance of the motor windings

How to check the condition of the electric motor winding

At first glance, the winding is a piece of wire wound in a specific way and there is nothing to break in it. But she has features:

serious selection of homogeneous material along the entire length;

clear calibration of shape and cross section;

applying a layer of varnish in industrial conditions, which has the highest insulating qualities;

strong contacts.

If at any point of the wire any of these requirements is violated, then the conditions for the passage of the electronic current change and the engine starts to work with reduced power or stops altogether.

To check one winding of a three-phase motor, you need to disconnect it from other circuits. What electric motors can be checked with a multimeter? Three-phase how to check the insulation. In all electric motors, they can be assembled according to one of 2 schemes:

The ends of the windings are usually brought out to the terminal blocks and marked with the signs "H" (beginning) and "K" (end). How to test an engine with a multimeter. From time to time, individual connections may be hidden inside the case, and other methods of designation are used for terminals, for example, by numbers.

A three-phase motor on the stator uses windings with similar electronic features that have equal resistances. If, when measured with an ohmmeter, they show different values, then this is already a reason to seriously think about the reasons for the scatter in readings.

How do faults appear in the winding

It is not possible to visually assess the quality of the windings due to the limited access to them. In practice, their electronic properties are inspected, taking into account that all winding faults appear:

breakage, when the integrity of the wire is violated and the passage of electronic current through it is excluded;

a small circuit that occurs when the insulation layer between the input and output turns is broken, characterized by the exclusion of the winding from work with shunting of the ends;

interturn short circuit, when the insulation is broken between one or more nearby turns, which are thereby taken out of operation. The current passes through the winding, bypassing the short-circuited turns, without overcoming their electronic resistance and without creating a certain work by them;

insulation breakdown between the winding and the stator or rotor housing.

Checking the winding for a broken wire

This type of malfunction is determined by measuring the insulation resistance with an ohmmeter. The device will show a huge resistance - ∞, which takes into account the section of the air space formed by the gap.

Checking the winding for a short circuit

The engine, inside the electronic circuit of which a short circuit has appeared, is turned off by protection from the power supply. But, even with a quick withdrawal from work by this method, the place where the short circuit appears is clearly visible visually due to the consequences of exposure to high temperatures with pronounced soot or traces of melting of metals.

With electronic methods for determining the resistance of the winding with an ohmmeter, a very small value comes out, very close to zero. Indeed, virtually the entire length of the wire is excluded from the measurement due to random shunting of the input ends.

Checking the winding for an interturn short circuit

This is a more hidden and difficult to detect malfunction. Several methods can be used to identify it.

Ohmmeter method

The device operates on a constant current and measures only the active resistance of the conductor. The winding, when working due to turns, makes a significantly huge inductive component.

When the 1st turn is closed, and their total number can be several hundred, it is very difficult to see the change in active resistance. After all, it varies within the limits of a few percent of the total value, and immediately less.

How to ring an electric motor

three-phase asynchronous electric motor, checking by a tester. In practice, quite verify electric motor

The location of the contacts of a three-phase motor and the continuity of the windings

We consider the placement of the ends of the windings three-phase motor, we determine whether they are connected correctly.

You can try to accurately calibrate the device and closely measure the resistance of all windings, comparing the results. But the difference in readings, even in this case, will not always be visible.

More accurate results can be obtained with a bridge method for measuring active resistance, but this is usually a laboratory method that is difficult for most electricians.

Measurement of consumption currents in phases

With an interturn circuit, the ratio of currents in the windings changes, and excessive heating of the stator appears. A good motor has similar currents. Therefore, their direct measurement in the current circuit under load more accurately reflects the real picture of the technical condition.

AC measurements

It is not always possible to find the impedance of the winding, taking into account the inductive component in a complete working circuit. To do this, you have to remove the cover from the terminal box and cut into the wiring.

For a motor that has been taken out of operation, a step-down transformer with a voltmeter and an ammeter can be used for measurement. To limit the current will allow a current-limiting resistor or a rheostat of the corresponding rating.

When measuring, the winding is inside the magnetic circuit, and the rotor or stator can be removed. There will be no balance of electrical flows, on the condition of which the engine is designed. About how to check the engine and can it be trusted with a multimeter? And how can. Therefore, a reduced voltage is used and the values ​​\u200b\u200bof currents are controlled, which should not exceed the nominal values.

The voltage drop measured across the winding divided by the current, according to Ohm's law, will give the value of the impedance. It remains to be compared with the features of other windings.

The same scheme allows you to remove the current-voltage properties of the windings. You just need to take measurements at various currents and write them down in tabular form or build graphs. If, when compared with similar windings, there are no serious deviations, then there is no inter-turn short circuit.

ball in stator

The method is based on the development of a rotating electric field with serviceable windings. How to check an electric motor with a multimeter step by step. To do this, they are supplied with a three-phase symmetrical voltage, but certainly a reduced value. For this purpose, three similar step-down transformers are usually used, operating in each phase of the power circuit.

To limit the current loads on the windings, the experiment is carried out for a short time.

A small metal ball from a ball bearing is introduced into the rotating magnetic field of the stator immediately after the coils are energized. If the windings are in good order, then the ball rolls synchronously along the inner surface of the magnetic circuit.

When one of the windings has an interturn circuit, the ball will hang at the fault.

During the test, the current in the windings must not exceed the nominal value and it should be taken into account that the ball freely jumps out of the body at the speed of departure from the slingshot.

Electrical check of winding polarity

The stator windings may not be marked at the beginning and end of the leads and this will make correct assembly more difficult.

In practice, 2 methods are used to search for polarity:

1. using a low-power constant current source and a sensitive ammeter showing the direction of the current;

2. by using a step-down transformer and a voltmeter.

In both versions, the stator is considered as a magnetic circuit with windings, operating by analogy with a voltage transformer.

Polarity check with battery and ammeter

On the outer surface of the stator, three separate windings are brought out by six wires, the beginnings and ends of which must be found.

With the help of an ohmmeter, they call and mark the conclusions related to each winding, for example, with the numbers 1, 2, 3. Then they arbitrarily mark the beginning and end on any of the windings. An ammeter is connected to one of the remaining windings with an arrow in the center of the scale capable of indicating the direction of the current.

The minus of the battery is aggressively connected to the end of the selected winding, and the plus is briefly touched at its beginning and immediately breaks the circuit.

When a current pulse is applied to the first winding, it is transformed due to electric induction into a second circuit closed through the ammeter, repeating its original shape. In this case, if the polarity of the windings is guessed correctly, then the ammeter needle will deviate to the right at the beginning of the pulse and move to the left when the circuit is opened.

If the arrow behaves differently, then the polarity is simply confused. It remains only to mark the conclusions of the 2nd winding.

Another 3rd winding is checked in the same way.

Polarity check with step-down transformer and voltmeter

Here, too, the windings are first called with an ohmmeter, determining the conclusions that relate to them.

Then, the ends of the first selected winding are arbitrarily marked for connection to a step-down voltage transformer, for example, 12 volts.

The two remaining windings are randomly twisted at one point with 2 leads, and the remaining pair is connected to a voltmeter and power is supplied to the transformer. Its output voltage is transformed into other windings with the same value, since they have an equal number of turns.

Due to the alternate connection of the 2nd and third windings, the voltage vectors will add up, and the voltmeter will show their sum. How to check the parking sensors sensor with a multimeter (tester. In our case, if the direction of the windings coincides, this value will be 24 volts, and with different polarity - 0.

It remains to mark all the ends and perform a control freeze.

The article gives a general procedure for checking the technical condition of some random motor without certain technical features. They are subject to change on a case-by-case basis. See the documentation for your hardware for details.

To find out the cause of the problem of the electric motor, it will not be enough just to inspect it, you need to carefully check it. You can quickly do this with an ohmmeter, but there are other ways to check. How to check the electric motor, we will describe below.

Motor Inspection

First, the test begins with a thorough inspection. In the presence of certain defects of the device, it can fail much earlier than the deadline. Defects may appear due to improper operation of the engine or its overload. These include the following:

• broken stands or mounting holes;
• the paint in the middle of the engine has darkened due to overheating;
• the presence of dirt and other foreign particles inside the motor.

The inspection also includes checking the markings on the motor. It is printed on a metal nameplate., which is attached to the outside of the engine. The label contains important information about the technical specifications of this instrument. As a rule, these are parameters such as:

• information about the manufacturer of the engine;
• model name;
• serial number;
• the number of revolutions of the rotor per minute;
• device power;
• a diagram of connecting the engine to certain voltages;
• a scheme for obtaining one or another speed and direction of movement;
• voltage - requirements in terms of voltage and phase;
• dimensions and type of case;
• description of the stator type.

The stator on the electric motor can be:

• closed;
• blown by a fan;
• splashproof and other types.

After inspecting the device, you can begin to check it and you need to do this starting with the engine bearings. Very often, electric motor malfunctions occur due to their breakdown. They are needed so that the rotor moves smoothly and freely in the stator. Bearings are located at both ends of the rotor in special niches.

For electric motors, the most commonly used types of bearings are:

• brass;
• ball bearings.

Some need to be equipped with grease fittings, and some are already lubricated during production.

Bearings should be checked as follows:

• place the engine on a hard surface and place one hand on top of it;
• turn the rotor with the other hand;
• try to hear scratching sounds, friction and uneven movement - all this indicates a malfunction of the device. A serviceable rotor moves calmly and evenly;
• we check the longitudinal play of the rotor, for this it needs to be pushed by the axis from the stator. Play is allowed up to a maximum of 3 mm, but not more.

If there are problems with the bearings, then the electric motor is noisy, they themselves overheat, which can lead to the failure of the device.

The next stage of verification is checking the motor winding for a short circuit on his body. Most often, a household motor will not work with a closed winding, because a fuse will burn out or a protection system will work. The latter is typical for ungrounded devices designed for a voltage of 380 volts.

An ohmmeter is used to check the resistance. You can check the motor winding with it in this way:

• set the ohmmeter to the resistance measurement mode;
• we connect the probes to the desired sockets (as a rule, to the common “Ohm” socket);
• select the scale with the highest multiplier (for example, R*1000, etc.);
• set the arrow to zero, while the probes should touch each other;
• we find a screw for grounding the electric motor (most often it has a hex head and is painted green). Instead of a screw, any metal part of the case can be used, on which the paint can be scraped off for better contact with the metal;
• we press the probe of the ohmmeter to this place, and press the second probe in turn to each electrical contact of the engine;
• Ideally the pointer of the measuring device should deviate slightly from the highest resistance value.

During operation, make sure that your hands do not touch the probes, otherwise the readings will be incorrect. The resistance value must be shown in million ohms or MΩ. If you have a digital ohmmeter, some of them do not have the ability to set the device to zero, for such ohmmeters the zeroing step should be skipped.

Also, when checking the windings, make sure that they are not short-circuited or broken. Some simple single-phase or three-phase electric motors are tested by switching the range of an ohmmeter to the lowest, then the needle goes to zero and a resistance measurement is made between the wires.

To make sure that each of the windings is measured, you need to refer to the motor circuit.

If the ohmmeter shows a very low resistance value, then it either exists, or you touched the probes of the device. And if the value is too high, then this indicates a problem with the motor windings, for example, about the gap. With a high resistance of the windings, the engine will not work at all, or its speed controller will fail. The latter most often concerns three-phase motors.

Checking Other Parts and Other Potential Problems

Be sure to check the starting capacitor, which is needed to start some models of electric motors. Basically these capacitors are equipped with a protective metal cap inside the motor. And to check the capacitor you need to remove it. Such an inspection may reveal signs of a problem, such as:

• oil leakage from the condenser;
• the presence of holes in the body;
• swollen capacitor case;
• unpleasant odors.

The capacitor is also checked with an ohmmeter. The probes should touch the terminals of the capacitor, and the resistance level should first be small, and then gradually increase as the capacitor charges with battery voltage. If the resistance does not increase or the capacitor is short-circuited, then most likely it is time to change it.

The capacitor must be discharged before retesting.

We proceed to the next stage of checking the engine: the rear of the crankcase, where the bearings are installed. In this place a number of electric motors are equipped with centrifugal switches, which switch start capacitors or circuits to determine the number of revolutions per minute. You also need to check the relay contacts for burntness. In addition, they should be cleaned of grease and dirt. The switch mechanism is checked with a screwdriver, the spring should work normally and freely.

And the final step is to check the fan. We will look at it using the example of checking the fan of a TEFC engine, which is completely closed and air-cooled.

Make sure the fan is securely attached and not clogged with dirt or other debris. The holes in the metal grill must be sufficient for free circulation of air, if this is not provided, then engine may overheat and subsequently it will fail.

The main thing when choosing an electric motor is its selection in accordance with the conditions where it will be used. For example, for a humid environment, splash-proof devices should be selected, and open-type devices should absolutely not be exposed to liquid. Remember the following:

So, we have listed the most common problems that can happen with household electric motors. Almost all of them can be recognized and certain measures taken by checking the device. And how to check it correctly and what details you should pay attention to first of all, we examined above.

Currently, many household appliances are used, the work of which is associated with an electric motor. Its malfunction causes anxiety and deprives the usual comfort. The multimeter is a universal measuring device that allows you to independently carry out the primary diagnosis of the unit.

What tools are needed

First of all, you will need the device itself. But before you ring the electric motor with a multimeter, you need to know the principles of operation of this device.

The main functions of the standard meter allow you to measure with sufficient accuracy:

• the value of the active resistance of the circuit to electric current;
• constant pressure;
• AC voltage.

Some models additionally give a check:

• the integrity of the electrical circuit by continuity;
• the capacitance value of the capacitor.

To open the cases of equipment and motors, you need screwdrivers, wrenches, pliers, a hammer. Thanks to this set, as well as minimal knowledge in electrical engineering, the question of how to check the electric motor with a multimeter is easy to identify faults that are fixed on their own.

Complicated damages are eliminated by service workshops, where there is precise equipment.

What electric motors can be checked with a multimeter?

Electric machines use the principle of rotation of the moving part relative to the static due to the magnetic induction that occurs in the coils through which the electric current flows. Depending on the type of food, they are divided into the following:

Electric motors are powered by:

• Constant, with circuit solutions to simplify the adjustment of power, speed.
• Variable, single or three-phase. They are separated:
  • synchronous, their rotor speed coincides with the frequency of change in the stator induction;
  • asynchronous. The number of revolutions does not depend on the network. The rotors of such engines differ in the winding connection scheme, they can be:
    • short-circuited, where the role of the windings is performed by aluminum or copper rods cast into the surface at an angle to the axis of rotation, connected at the ends of the rotor by rings;
    • phase: the ends of the coil laid in the grooves of the core are connected by a "star" or "triangle" with contact lamellas on the rotor shaft.

The phase rotor is more complex, its starting characteristics are better, the adjustments are wider. But more often they use a squirrel-cage rotor because of the simplicity of design, high reliability, and lower price.

Checking the electric motor by external inspection

Before checking the motor winding with a multimeter, you need to examine the motor disconnected from the mains along with the power cord to look for mechanical damage, signs of insulation breakdown or overheating. The motor axle should rotate easily in the bearings, without jamming or jamming. There should be no smell of burnt insulation, oil spills, sagging.

The absence of visible damage may require disassembly of the motor to inspect the graphite brushes, contact lamellas, the condition of the coils, their conclusions. Closing the electrical circuit causes heating, which is manifested in clearly visible color changes near the breakdown of the insulation.

How to find an open or interturn circuit

If no signs of damage are visible, then it's time to start measuring with a digital tester. To do this, do the following:

1. Insert the test leads into the sockets on the front panel.
2. Select the continuity with the mode switch, connect the bare ends of the probes, the meter will beep. The break will stop the sound. This checks the presence, serviceability of the battery, measuring cords, sockets. This mode allows you to ring the circuit without looking at the indicator, by ear.
3. If the device is without a buzzer, the resistance measurement mode is switched on at the lowest limit, usually it is “200” Ohm. The alignment of the cord tips will be reflected on the multimeter indicator with numbers indicating the resistance of the probe wires in the range of 0.6 ÷ 1.5 Ohm.

A break is searched for by dialing or measuring the resistance of wires, cords, all coils, having previously disassembled the connection of their ends. The rotor is tested by measuring each pair of leads.

The interturn short circuit of windings made of relatively thick wire with a small one cannot be determined. Shorting a few turns will reduce the total resistance by fractions of an ohm not shown on the display.

Checking the insulation of the windings relative to the housing

Using a multimeter in the maximum resistance measurement mode, you can make sure that there is no bad insulation, shorts to ground. It's life-threatening.

Everything is checked on the motor disconnected from the network. One probe of the device is connected to the case, the second one touches all the winding terminals. The indicator should show an open, or large, hundreds of megaohms, resistance in all cases.

Then you need to check the absence of insulation breakdown between the windings, for which the probes are connected in pairs to the terminals of different coils. The indicator should not show resistance.

Checking asynchronous three-phase motors with a squirrel-cage rotor

A three-phase motor with a multimeter is checked quickly. Having disassembled the ends, measure the resistance of each of them with a multimeter. The difference in values ​​must be less than 10%. Along the way, you need to make sure that there is no breakdown on the body between the coils.

The exact location of the interturn circuit will be shown by a device made of a step-down three-phase transformer; the stator of the disassembled motor is connected to the terminals. Power is supplied, a metal ball is placed inside, which, with good windings, rolls along the inner surface. If there is a short circuit in the turns, the ball will stick in this place.
Repairmen use current clamps. Each phase coil of the same resistance passes the same current if there is no phase voltage imbalance. If there is more current in one, most likely there is an inter-turn malfunction.

Checking capacitor motors

An asynchronous motor, where in series with one of the coils of which a capacitance is connected to create a current phase shift, is a capacitor motor. The test of such an electric motor, in addition to continuity, includes a check of the capacitance, which is selected to create a phase shift between the coils equal to 90 degrees, so that the rotor torque is maximum.

The capacitance of the working capacitor is relatively small, you can check it if the multimeter can measure the capacitance by connecting to the terminals of a part that is disconnected from the motor circuit, after briefly shorting its terminals.

Checking motors with a phase rotor

Testing a wound rotor motor is similar to testing a conventional induction motor, the rotor windings are additionally measured. Their connection scheme is performed by a “star” for a three-phase supply network with a voltage of 380 volts, or a “triangle” is used for a 220 network.

Measurements with a multimeter are carried out according to the same method as for the stator.

Checking the starting capacitor

A confident start of the electric motor occurs when, at the moment of power-up, a starting capacitor is briefly connected in parallel with the working capacitance. It serves to create a circular magnetic field at the start, after the start of rotation of the rotor it turns off. The starting capacitor is easy, even if it does not have a capacitance measurement mode:

1. The capacitor, having previously been discharged by closing the terminals, is disconnected from the motor circuit, carefully inspected. If there are cracks, swelling of the case, or other visible damage, the container can be changed to a new one without checking.
2. Set the resistance measurement mode on the tester to the limit of 2000 kilo-ohms, check the operability by briefly connecting the measuring probes.
3. Connect the probes to the terminals of the capacitor. Discharged, it will begin to quickly charge from the probes of the device. Its capacity is relatively large, much more than that of a working capacitor. The multimeter indicator will first show a small resistance, which will increase as the capacity is charged, because the charging current gradually decreases. At the end of the process, the multimeter will show an infinitely large resistance, an open.
4. Reverse the polarity of connecting the probes to the capacitor, see the increase in resistance, with an indication of a break at the end of the measurement. This will confirm that the capacitor is good.
5. Check the breakdown of the plates on the capacitor case, if it is metal, by measuring the resistance between the part case and each of the terminals in turn.

The tester indicator should show a break. Other values ​​are a sign of a malfunction.

Repair of asynchronous motors

Identified damage must be repaired. Some of them are easy to do at home, “on your knee”, checking the electric motor with a 220 volt multimeter is quite simple. Others will require contacting an electrical repair shop, where they can repair both mechanical damage and replace or rewind the coils.

You can not start a complex repair without conditions, a base of experience and knowledge.

Winding insulation test

The operational reliability of the electric motor is determined by the condition of the insulation. Vibration of a running engine, thermal, chemical processes worsen the electrical insulating properties. Therefore, when diagnosing after repair, it is necessary to test the insulation in an electrical laboratory.

There is a test transformer, the secondary high voltage of which is supplied between one of the windings and the remaining coils connected to the motor housing. Test voltage values:

If the repair was done by hand and cannot be checked with a stand, you need to test the motor insulation with a megohmmeter. It supplies high voltage, which is not in the multimeter.

When checking the electric motor with a 380 volt multimeter, you need to take into account that the work is carried out with the network turned off. Working with electricity requires composure, attention, so as not to get an electric shock. Observing safety measures, checking the health of the unit is quite simple.

When an electric motor is not working, it may not be enough just to look at it to understand the reason. An electric motor that has been stored in a warehouse for a long time may or may not work, regardless of its appearance. A quick check can be done with an ohmmeter, much more information is given below to correctly assess the condition of the electric motor.

Steps

Part 1

Part 2

Start by checking the motor bearings. Many electrical motor failures are caused by failed bearings. Bearings allow the shaft (rotor) to rotate freely and smoothly in the stator. The bearings are located at both ends of the motor rotor shaft in bell-shaped niches.

• There are several types of bearings that are used in electric motors. The two most popular types are brass plain bearings and ball bearings. Many of them have fittings for lubrication, others are lubricated at the factory ("maintenance free").

1. Perform a bearing check. To perform a quick check of the bearings, place the motor on a hard surface and place one hand on top of the motor, spin the rotor with the other hand. Watch carefully, try to feel and hear friction, scratching sounds, uneven rotation of the rotor. The rotor must rotate quietly, freely and evenly.

   Then check the longitudinal play of the rotor, push, pull the rotor by the axle from the stator. A little play is acceptable (in the most common household motors, play should be no more than 3 mm), but the closer it is to "0", the better. An engine with bearing problems runs noisily, the bearings overheat, resulting in engine failure.

Part 3

Check the motor windings for a short to ground. Most household electric motors with closed windings will not work: most likely a fuse will blow or a circuit breaker will trip (motors rated for 380 volts are "ungrounded", so such motors can be operated with windings closed to the case, while the fuse will not blow).

Use an ohmmeter to check the resistance. Set the ohmmeter to resistance measurement mode, connect the probes to the appropriate sockets, usually the "common" and "Ohm" sockets (refer to the meter's instruction manual if necessary). Select the scale with the highest multiplier (R*1000 or similar) and set the pointer to “0” by touching the probes to each other. Find a screw designed to ground the motor (they are often green, with a hex head) or any metal part of the case (if necessary, to establish good contact with metal, you need to scrape off the paint) and press one ohmmeter probe to this place, and the other probe in turn to each of the electrical motor contacts. Ideally, the ohmmeter needle should barely deviate from the highest resistance. Make sure your hands do not touch the probes as this will result in inaccurate measurements.

• The ohmmeter should indicate a resistance value in millions of ohms (or "MΩ"). Sometimes the value can reach only a few hundred thousand ohms (500,000 or so). This may be acceptable, but the greater the resistance value, the better.
• Many digital ohmmeters don't offer the ability to set the meter to "0", so skip "zeroing" if you have a digital ohmmeter.

1. Make sure the motor windings are not broken off or short-circuited. Many simple single-phase and 3-phase motors (used in household appliances and in industry, respectively) can be tested by simply switching the range of the ohmmeter to the lowest (RX*1), set the needle to zero again, and again measure the resistance between the motor wires. Refer to the motor schematic to make sure you measure each winding.

   • You can see a very low resistance value. The resistance value can be quite low. Make sure that your hands do not touch the ohmmeter probes, as this will cause inaccurate meter readings. A high resistance value indicates a potential problem with the motor windings, which may be open. A motor with high resistance windings will not run or its speed controller will not work (this may be with 3-phase motors).

Part 4

1. Check the start capacitor used to start some motors. Most capacitors are protected from damage by a metal cover on the outside of the motor. It is necessary to remove the cover to gain access to the capacitor to check it. A visual inspection will help detect oil leaks from the condenser, holes in the case, a swollen condenser case, burning or smoke smells - all of these indicate potential problems.

   • Capacitor testing can be done with an ohmmeter. Touch the probes to the terminals of the capacitor, the resistance should start at low values ​​and gradually increase, as the small voltage supplied from the ohmmeter batteries gradually charges the capacitor. If the capacitor remains short-circuited or the resistance does not increase, then the capacitor is probably the problem and needs to be replaced. The capacitor must be discharged before attempting this test again.

2. Check the rear of the crankcase where the bearing is installed. There, some motors have centrifugal switches used to switch the starting capacitor or to connect circuits that determine the number of revolutions per minute. Check the relay contacts for burnt, clean them of dirt and grease. Use a screwdriver to check the switch mechanism, the spring should work freely.

   Check fan. Type "TEFC" (totally enclosed, air-cooled motor). This type of motor has the fan blades behind a metal grill on the back of the motor. Make sure the fan is secure and not clogged with dirt or other debris. The holes in the metal grill must allow free air movement, otherwise the engine may overheat and fail.

3. Choose the right motor for the conditions in which it will operate. Splash-proof motors are used in wet environments, and open motors should not be exposed to water or moisture.

   • Splash-proof motors can be installed in wet or damp locations and are designed so that water (or other liquids) cannot enter the motor by gravity or by the flow of water (or other liquid).
   • An open engine, as the name suggests, is completely open. From the ends, these motors have rather large holes, and the stator windings are clearly visible. These openings must not be blocked and these motors must not be installed in damp, dirty or dusty locations.
   • TEFC motors, on the other hand, can be used in all of the areas mentioned above, but they should also not be used in conditions for which they are not designed.

• This is not to say that it is rare for motor windings to be both "open" and "short" at the same time. At first glance, this may seem like an oxymoron, but it really isn't. An example would be an "open" circuit caused by a foreign object that has entered the motor, or an excessive supply voltage that literally causes the wires in the windings to melt and break the circuit. If the end of the molten copper wire comes into contact with the motor frame or other grounded part of the motor, this will result in a "short circuit". This doesn't happen often, but it can happen.
• A NEMA Quick Reference Refer to this link for typical motor housings and dimensions.

DC motors are widely used. Especially in the automotive industry. They are necessary for the operation of power windows and wipers, are included in the car's cooling system, etc.

The reliability of the entire device depends on the quality and performance of such engines. On the site http://www.sbpower.ru/brands/allen-bradley you will find only the highest quality motors and other electrical products.

Checking the integrity of the windings

DC motors are called collector motors. Their performance can be checked using a device called a multimeter. All actions are performed in this order:

1. The tester enters the resistance measurement mode (Ohm). The probes are applied in pairs to the collector lamellas. If the engine is running, the readings will be the same.
2. For a running engine, the resistance will be infinitely high if you simultaneously attach the probes to the armature and the collector.
3. Motor failure may be due to a broken winding. Using the device, we check for the presence of these defects.
4. One probe touches the stator box, and the second is applied to the motor leads. A low value will indicate a malfunction.

There are other types of engine checks, but they are used by craftsmen who repair various appliances. At home, you can limit yourself to the method described above.

Other types of checks

You can check the health of the engine in other ways. There are special devices that allow you to check the armatures of DC motors. You need to attach the engine to a special prism of the device, and then plug it into the network. During the diagnostic process, you need to slowly turn the engine. An interturn short circuit is indicated by vibration and attraction of the interturn web to the groove.

In order to quickly check the engine, you can use special working stands. This is a special design, consisting of a DC source, an inverter, a digital voltmeter, a voltage comparator, an indicator light and a buzzer that signals a break.

The stand can be assembled independently, but this is advisable if you are engaged in the diagnosis and repair of DC motors. At home, to check, it is enough to use a simple tester, which can be purchased at any electrical store at an affordable price.