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 correctly conduct the preparatory phase, at the stage of which you need to check the foundation, as well as assess the location and size of all the holes used to attach the equipment.
Preparing the engine for installation
In addition to the fact that it is necessary to prepare the 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 comes to the installation site already assembled. In the event that the rules of transportation and storage of this equipment were not violated, then it is not necessary to disassemble it for inspection. In such cases, you need to proceed with the following steps:
- first you need to conduct a full external examination;
- then you need to start cleaning the fundamental plates and feet 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 solvent to get rid of dirt;
- after these actions, it is necessary to inspect parts such as terminals, brush mechanisms, collectors;
- all bearings are checked separately;
- Before mounting the electric motor, it is necessary to measure the gaps between all important parts, for example, between the shaft and seals;
- a separate procedure is checking the air gap, which is located between the movable part of the rotor and the stator;
- it is necessary to inspect the entire rotating part of the rotor so that it does not touch any other parts of the machine, and make sure with the megger that the necessary resistance of the windings is present.
For all inspection of equipment, a special stand is allocated, which is located in a separate room. After conducting the inspection and before mounting the electric motor, the electrician who performed the inspection must report the presence or absence of defects to the senior worker.
If no external damage was found during the inspection, then you need to conduct another preparatory procedure. Blow out the unit with compressed air. But before that, you need to check the device itself so that it delivers only dry air. To do this, it will be enough to point it at another subject and turn it on. During the purge, you must manually rotate the rotor to make sure that the shaft rotation in the bearings is free. Outside, the engine must be completely wiped with a cloth that is wetted with kerosene.
Work with bearings
There are many different versions of electric motors according to the installation method, but for all there are some general operations that need to be carried out in any case. Flushing of plain bearings refers to this type of work. There are several ways to achieve the desired result.
First you need to remove all residual oil from the parts, for which it is necessary to unscrew the drain plugs. After this, the plugs are screwed back, and instead of oil, kerosene is poured. You cannot turn on the device, you need to manually rotate the rotor or the equipment armature. Thus, you can remove all residual oil, and then drain the kerosene in the same way that the oil was merged. But this is not the end and it is necessary to rinse again, but this time with fresh oil, which also merges. Only after performing these two operations can you fill the bath 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 design of the electric motor by mounting method are not washed. The only requirement is that the amount of oil does not exceed 2/3 of the total volume.
Carrying out measuring work before installation
Installation work includes the stage at which you want to check the insulation resistance.
If the DC motor, then the resistance test is carried out between the armature and the excitation coil, in addition, it is necessary to check the insulation of the armature itself, as well as the brushes and excitation coils with respect to the motor housing. Naturally, if the motor itself is connected to the network, before to start the measurement, it is necessary to disconnect all the wires that go from the network and the rheostat to the equipment.
Installation and commissioning of 3-phase current motors with a squirrel-cage rotor should be accompanied by a measurement of the insulation resistance of the stator windings with respect 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 on the outside there are only 3 ends of the windings, then you need to check the insulation of the winding in relation only to the housing.
The technology for mounting electric motors with a phase rotor differs in that here insulation measurements must be carried out between the rotor and the stator, as well as the insulation of the brushes with respect to the housing.
As for the instrument for measuring insulation, a megger 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 engine power is higher, then the megohmmeter should be rated at 2.5 kW.
Unit installation and connection to mechanisms
If with the type of electric motor, the installation and preparation of which greatly depends on its purpose and the rotor itself, everything has become somewhat clearer, then you need to figure out the connection between the device and other mechanisms. 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 the electrical appliance and other mechanisms, a clutch or a belt or gear transmission is used for this. Any installation of the electric motor for installation needs to check the position in the horizontal plane with the help of a level, and this must be done in two mutually perpendicular planes. The “gross” level, which has a special recess suitable for the motor shaft, is best suited for this.
Electric motors can be installed both on a concrete floor and on a foundation. In any case, metal pads must be placed under the feet of the bed to very accurately adjust the position of the device in the horizontal plane. For this, for example, wooden linings cannot be used, since when they tighten the bolts they are compressed, and when pouring the foundation 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 strictly observe the parallelism of its shafts, as well as the mechanism connected to them. The same rule applies to the midline, which should match the entire width of the pulleys. In the event that the width of the pulleys coincides, 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, it is necessary to attach a ruler to the ends of the pulleys and adjust the electric 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. The adjustment takes place until the distance from the bracket to the pulley is the same.
Centering Shafts
Another major operation, which is necessarily included in the installation process of an electric motor, is the alignment of the shafts, which are interconnected, as well as the mechanisms. This is done in order to completely eliminate the possibility of lateral and angular displacements of these parts.
During this operation, probes, micrometers or indicators are used, with which, lateral and angular clearances are measured. It is very important to note that when performing work with the help of a probe, errors are not excluded. Its percentage depends directly on the employee who is involved in measurements, on his experience. If the alignment was carried out correctly, then the numerical sum of the even measurements should coincide with the sum of the numerical value of the odd measurements.
Why center the motor shaft on pumping equipment?
The 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 of both the motor shafts and the pump shafts coincide. If you do not carry out such work, then the risk of breakdown of parts such as couplings or gears - toothed or belt - is greatly increased.
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 borehole pump with an electric motor is installed, and they are connected using a half coupling, then the excessive load will fall on the bearing, because of which it will also fail very quickly. In any case, installation, maintenance of electric motors should always be accompanied by a check or adjustment of the shaft alignment.
Methods of centering the engine 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 align the motor shafts and the shaft of the 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 previously described are still often used. It is worth adding here that before starting work, it is very important to decide what to customize and what. In other words, you need to understand what is more convenient to customize - the motor shaft under the pump shaft or vice versa.
Installation work of the engine with a phase rotor
Here it’s worth mentioning right away that mounting a type of asynchronous electric motor with a phase rotor is similar to mounting with a squirrel-cage rotor. The only difference is that for normal operation of the phase rotor, it is necessary to additionally carry out such tasks 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 secured sufficiently reliably. To do this, use a wrench to tighten all existing nuts. After this stage, you can proceed to check the insulation of the winding, and how this is done is described earlier.
There are some nuances here. Continue installation after checking the insulation resistance if the value is not lower than 1 mOhm. In the event that this numerical value is lower, then it is considered reduced and you need to look for the cause of this defect. 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 are not touching the motor housing. Another reason is also possible - damping of the insulating plate, on which the stationary contacts are usually located. If this is the case, then it is necessary to carry out a drying procedure for all damp parts. To do this, either a special drying cabinet or an electric lamp is used.
Slip rings and rotor
Installation of an asynchronous electric motor with a phase rotor 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 should also be checked. It is very important to check the reliability of the fastening of all wires, and in addition, the insulation resistance and the absence of breaks in the circuit are separately checked. This is all done with a megger.
After checking the value of the insulation resistance of the rings and the winding, the numerical value should not be less than 0.5 mOhm. If the value is lower, then you will have to look for the reason for the decrease, and also individually check the resistance of each ring and winding. In this case, as in the previous one, lowering can occur due to dampening of the winding of the rings or of the windings. In this case, you have to carry out the drying. However, if after that the resistance has not returned to normal, then you will have to remove each ring individually and look for the cause of the decline. It is forbidden to start an electric motor with reduced resistance.
Explosion proof electric motor
Some enterprises need to install explosion-proof engine models. Each such device is brought to production in an already assembled form, and with it always deliver instructions for its use, as well as for its installation. This is quite important, since all work on its disassembly is carried out only if there is a reduced resistance or open circuit in the circuit.
If the power of an explosion-proof type of motor is 6 or 10 kW, then to measure the resistance of the winding you need to use a megohmmeter, which is designed for 2.5 kW. The numerical value should not be lower than 6 mOhm. If everything is in order, then you can start connecting.
It is important to pay attention to the input of wires and cables, which usually follows the instructions that are attached to the engine. If such types of cables as ABVG and BVG need to be brought to an explosion-proof device during installation, then from the main cable route they are laid open on trays or mounting profiles. In this case, no additional protection with this wire is required. In addition, this rule applies regardless of the height at which the line will be laid.
It is worth saying that all types of engines have a special marking that indicates how they should be installed, as well as their design. In this case, we mean that from the designation you can find out how and where exactly all the necessary fastening elements are located. Mounting, dismantling 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 are the numbers from 0 to 7, and they indicate the method of mounting the motor. Another important design parameter that is also indicated is the direction of the shaft end. The third digit indicates it (the value can be from 0 to 9).
The installation estimates for an electric motor are usually based on these three factors.