Installation of electric motors: expert advice

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

Today, there are many different types of electric motors. All of them differ not only in size, but also in technical indicators, as well as installation rules, which is most important. Because of this, the installation of electric motors has to be approached very responsibly. It is also very important to carry out the preparatory stage correctly, at the stage of which you need to check the foundation, as well as evaluate the location and size of all the holes used to mount the equipment.

Preparing the engine for installation

In addition to the fact that it is necessary to prepare a site for mounting the electric motor, it is necessary to carry out certain work on the preparation of the device itself before starting work. It is important to note here that the electric motor arrives at the object for installation already assembled. In the event that the rules for transporting and storing this equipment have not been violated, then there is no need to disassemble it for inspection. In such cases, you need to proceed with the following actions:

• first you need to carry out a fullexternal inspection;
• next, you need to start cleaning the foundation plates and paws of the bed;
• it is important to check the thread before fixing the device, for which they run the nuts, and also rinse the foundation bolts with a solvent to get rid of dirt;
• after these steps, you need to inspect parts such as terminals, brush mechanisms, collectors;
• all bearings are checked separately;
• before mounting the motor, work must be done to measure the gaps between all important parts, for example, between the shaft and seals;
• checking the air gap between the moving part of the rotor and the stator is considered a separate procedure;
• you need to inspect the rotating part of the rotor as a whole so that it does not touch any other parts of the machine, and make sure that the required resistance of the windings is present with a megohmmeter.

For carrying out all work on the inspection of equipment, a special stand is allocated, which is located in a separate room. After the inspection and before mounting the motor, the electrician who carried out the inspection must report the presence or absence of defects to the senior worker.

If no external damage was found during the inspection, then one more preparatory procedure should be carried out. The unit must be blown out with compressed air. But before that, you need to check the device itself so that it only supplies dry air. To do this, it will be enough to point it at another object and turn it on. During purge, you need to manuallyturn the rotor to make sure that the rotation of the shaft in the bearings is free. The outside of the engine must be completely wiped with a rag that is wetted in kerosene.

Working with bearings

There are many different versions of electric motors according to the method of installation, but for all there are some general operations that must be carried out in any case. The flushing of plain bearings belongs to this type of work. There are several ways to achieve the desired result.

First you need to remove all oil residues from the parts, for which you need to unscrew the drain plugs. After that, the plugs are screwed back, and instead of oil, kerosene is poured. It is impossible to turn on the device, you need to manually rotate the rotor or the armature of the equipment. In this way, all residual oil can be removed, and then the kerosene is drained in the same way that the oil was drained. But this is not the end yet and you need to flush again, but this time with fresh oil, which is also drained. Only after performing these two operations can the bath be filled 1/2 or 1/3 with fresh oil for work.

It is worth noting that only plain bearings are washed in this way. Rolling bearings for any version of the electric motor according to the installation method are not washed. The only requirement is that the amount of oil does not exceed 2/3 of the total volume.

Measuring before installation

Installation work includes a step that requires an insulation resistance test.

IfDC motor, then the resistance test is carried out between the armature and the excitation coil, in addition, it is required to check the insulation of the armature itself, as well as the brushes and excitation coils in relation to the motor housing. Naturally, if the motor itself is connected to the network, then before starting measurements, it is necessary to disconnect all wires that go from the network and the rheostat to the equipment.

Installation and adjustment of 3-phase electric motors with a squirrel-cage rotor must be accompanied by a measurement of the insulation resistance of the stator windings in relation to each other, as well as to the housing. However, such a procedure can only be done if all 6 ends are brought out. If there are only 3 ends of the windings outside, then you need to check the insulation of the winding in relation to the body only.

The technology of mounting electric motors with a phase rotor is different in that here insulation measurements must be carried out between the rotor and the stator, as well as the insulation of the brushes in relation to the housing.

As for the instrument for measuring insulation, a megohmmeter is used for this. If the power of the device is not more than 1 kW, then the device is taken with a maximum scale of up to 1 kW. If the motor power is higher, then the megger should be rated for 2.5 kW.

Installation of the unit and connection with mechanisms

If everything has become somewhat clearer with the type of electric motor, the installation and preparation of which is highly dependent on its purpose and the rotor itself, then further it is necessary to deal with the connection of the apparatus and othermechanisms. It is worth noting that if the weight of the equipment is not more than 50 kg, then it can be installed manually if the concrete platform is not too high.

As for the connection of an electrical appliance and other mechanisms, a clutch or a belt or gear transmission is used for this. Any version of the electric motor for installation needs to check the position in the horizontal plane using a level, and this must be done in two mutually perpendicular planes. The "gross" level is best suited for this, which has a special recess that fits under the motor shaft.

Electric motors can be installed both on a concrete floor and on a foundation. In any case, metal pads must be placed under the paws of the bed in order to very accurately adjust the position of the device in the horizontal plane. It is impossible to use, for example, wooden linings for this, since when the bolts are tightened, they are compressed, and when the foundation is poured, they can swell, which in any case knocks down the position of the machine.

As for the repair and installation of an electric motor with a belt drive, it is very important to accurately observe the parallelism of its shafts, as well as the mechanism connected to them. The same rule applies to the center line, which must match across the entire width of the pulleys. In the event that the width of the pulleys is the same, and the distance between the shafts does not exceed 1.5 meters, then all measurements can be carried out using a steel ruler.

To do everything right, you need to attachruler to the ends of the pulleys and adjust the motor until the measuring tool touches the two pulleys at 4 points. It also happens that the distance between the shafts is more than 1.5 meters, and there is no alignment ruler at hand. When repairing and installing an electric motor, in this case, you need to use a string and brackets that are temporarily attached to the pulleys. Adjustment occurs until the distance from the bracket to the pulley is the same.

Shaft alignment

Another important operation, which is necessarily included in the process of installing an electric motor, is the alignment of the shafts that are interconnected, as well as mechanisms. This is done in order to completely eliminate the possibility of lateral and angular displacements of these parts.

When carrying out this operation, feelers, micrometers or indicators are used, with the help of which side and corner clearances are measured. It is very important to note here that when performing work with a probe, errors are not excluded. Its percentage depends directly on the employee who is engaged in measurements, on his experience. If the alignment was carried out correctly, then the numerical sum of the even measurements should match the sum of the numerical value of the odd measurements.

Why center the motor shaft of pumping equipment?

Installation of electric motors for pumps is not too different from the installation of the same equipment. Here it is worth paying attention only to the alignment of the shafts. In this case, it is very important that the axes coincide asmotor shafts and pump shafts. If such work is not carried out, then the risk of breakage of such parts as clutches or gears - gear or belt greatly increases.

If we talk about the shortcomings of the belt drive in this case, then the belt itself will either constantly jump off or experience an increased load, which will lead to its faster wear. For example, if a downhole pump with an electric motor is installed, and they are connected using a coupling half, then an excessive load will fall on the bearing, which will also cause it to fail very quickly. In any case, the installation, maintenance of electric motors should always be accompanied by checking or adjusting the alignment of the shafts.

Motor alignment methods for pumping equipment

Today, there are many different ways to carry out this operation, but the most modern and accurate of them is the use of laser equipment. The use of these devices will allow in the shortest possible time and most accurately to carry out the alignment of the shafts of the electric motor and the shaft of pumping equipment or any other mechanism. However, this method has one significant drawback - the high cost of equipment, which greatly complicates the use of this method. Because of this, the more traditional shaft centering methods that were described earlier are still most commonly used. It is worth adding here that before starting work, it is very important to decide what and under what to customize. In other words, you need to understand thatit is more convenient to adjust - the motor shaft under the pump shaft or vice versa.

Installation work of a wound rotor motor

Here it is immediately worth saying that the installation of the type of an asynchronous motor with a phase rotor is similar to the installation with a squirrel-cage rotor. The only difference is that for the normal operation of the phase rotor, it is necessary to additionally carry out such work as starting the rheostat, checking the brushes and the brush lifting mechanism.

Before proceeding with the installation of the starting rheostat, you need to make sure that all contacts are fixed securely enough. To do this, use a wrench to tighten all available nuts. After this stage, you can proceed to checking the insulation of the winding, and how this is done was described earlier.

There are some nuances here. It is possible to continue installation after checking the insulation resistance if the value is not lower than 1 mΩ. In the event that this numerical value is lower, then it is considered low and the cause of this defect must be sought. To do this, the integrity of all parts of the winding is usually checked, and you also need to make sure that the lead ends do not touch the motor housing. Another reason is also possible - this is the dampness of the insulating plate, on which the fixed contacts are usually located. If this is the case, then it is necessary to carry out the drying procedure for all damp parts. For this, either a special drying cabinet or an electric lamp is used.

Slip rings and rotor

Installation of an asynchronous electric motor with phaserotor or its repair, if required, is carried out with a mandatory check of the rotor winding, the output ends of the winding, slip rings and brushes must also be checked. It is very important to check the reliability of fastening of all wires, and besides this, the insulation resistance and the absence of breaks in the circuit are checked separately. This is all done with a megohmmeter.

After checking the insulation resistance value of the rings and winding, the numerical value should not be less than 0.5 mΩ. If the value is lower, then you will have to look for the cause of the decrease, and also separately check the resistance of each ring and winding. In this case, as in the previous one, a decrease can occur due to dampness of the winding of the rings or windings. In this case, you will have to dry. However, if after this the resistance has not returned to normal, then you will have to remove each ring separately and look for the cause of the decrease. It is forbidden to start up a reduced resistance motor.

Explosion-proof motor

In some plants there is a need to install explosion-proof models of the engine. Each such device is brought to production already assembled, and instructions for its use, as well as for its installation, are always delivered with it. This is quite important, since all disassembly work is carried out only if there is reduced resistance or open circuits.

If the power of the explosion-proof type of motor is 6 or 10 kW, then a megohmmeter must be used to measure the resistance of the winding, which is ratedat 2.5 kW. The numerical value must not be lower than 6 mΩ. If everything is in order, then you can start connecting.

Here it is important to pay attention to the input of wires and cables, which usually follows the instructions that come with the engine. If during installation it is necessary to connect cable brands such as ABVG and BVG to an explosion-proof device, then from the main cable route they are laid open on trays or mounting profiles. In this case, no additional protection is required for this wire. In addition, this rule applies regardless of the height at which the line will be laid.

It is worth mentioning that all types of engines have a special marking that indicates exactly how they should be installed, as well as their design. In this case, it means that from the designation you can find out how and where exactly all the necessary fasteners are located. Installation, dismantling of the electric motor is greatly simplified if the marking is correctly understood. As for the design, it is indicated by numbers from 1 to 9 and is indicated at the very beginning of the marking. Next come the numbers from 0 to 7, and they indicate the method of mounting the electric motor. Another important design parameter that is also indicated is the direction of the shaft end. It is indicated by the third digit (the value can be from 0 to 9).

Motor installation estimates are usually based on these three factors.