Electric motors, both AC and DC, are designed for a service life of 15-20 years (usually). Subject to the rules of operation and timely maintenance, electrical machines last longer than this period. In the article we will tell the readers of the site Electrician himselfwhat affects the life of the electric motor and how it can be extended.
Content:
- Electric motor selection rules
- Operating tips
- Maintenance
Electric motor selection rules
In order for the standard service life not to decrease during the operation of the engine, it is necessary initially to correctly approach the choice of an electric machine. A few simple rules:
- The ambient temperature and humidity of the place where the electric motor will be installed must correspond to the climatic version of the engine. In this case, it is necessary to take into account that the electric machine will heat up when operating under load, respectively, the air temperature will increase.
- The power of the electric motor must be 10% higher than the power of the consumers (we are talking about the load capacity, power and torque required to drive the actuators in motion). In accordance with GOST, when designing an electric power system, the power of the electric motor is taken with a margin of 10% of the nominal.
- The choice of explosion-moisture-dust protection (according to the standard IP) the engine must be suitable for the operating conditions of the machine. Degrees of protection, types of execution and categories of placement of electrical equipment are regulated by GOST R IEC 60034-5-2007.
- Choice type of electric motor, synchronous or asynchronous, must correspond to the nature of the load and the mode of use (long-term, short-term, intermittent, and others). With the wrong choice of engine for the mechanism, its service life is significantly reduced. So do not use the motor from a winch, crane or gate valve drive to drive fans or pumps.
- The voltage and current of the electric motor must be selected taking into account the possibility of the power supply of the enterprise. To reduce inrush currents (especially for powerful electric motors), it is worth choosing an electric machine with start-up by switching from "Stars" to "triangle". For this, the rated voltage of the "delta" must be equal to the line voltage of the supply network, in most cases these are motors with a rated voltage of 380/660 V.
The choice of an electric motor must be entrusted to a professional. Because there are many more features that arise during operation and affect the service life. This is the moment of load on the shaft and energy efficiency and many others.
Operating tips
The manufacturer's instructions are attached to each product. Throughout the entire service life of the electric motor, it is necessary to strictly adhere to the requirements and recommendations described in it. If necessary, or to clarify any controversial issues, you can make a request to the manufacturer.
In operation, throughout its entire service life, the electric motor needs daily, weekly or other frequency control and inspection:
- measurement of winding insulation resistance rotor and stator (also carried out before each launch);
- measuring the temperature of the windings (at rated load);
- temperature control of bearings (organoleptic method is allowed);
- control engine vibration and the driven mechanism.
It is unacceptable to use the electric motor in rooms without ventilation, this leads to increased heating of its windings, as a result, the service life is significantly reduced. It is also necessary to control the humidity in the room, moisture from the air can condense into the electric motor due to the temperature difference, which will lead to a decrease in the insulation resistance and an increased heating the windings. Motor bearings can also suffer from condensation, especially after long periods of inactivity.
One of the most common causes of motor failure is power quality. Power quality is determined GOST 32144-2013. With a decrease in the supply voltage, the stator current increases and, accordingly, the windings are heated. Heating the windings will significantly shorten the life of the insulation.
Due to the increased voltage, there is an increase in the stator magnetic flux, magnetizing current, which leads to heating of the core. Temperatures reach critical levels, up to a steel fire. In addition, due to the increased supply voltage, reactive power is taken from the network, which negatively affects consumers.
Maintenance
Maintenance should be carried out within the timeframe and in the amount specified in the operating instructions. Maintenance is also regulated by documents: Rules for the technical operation of consumer electrical installations (PTEEP) and Electrical installation rules. Subject to all the requirements set forth in the instructions for the device and regulatory documents, the engine service life will exceed that specified in the data sheet.
With a power of electrical installations up to 100 kW, as a rule, three-phase asynchronous electric motors with a squirrel-cage rotor are chosen. This is due to the simplicity of design, ease of maintenance and use in operation, high reliability and low cost. Maintenance of such engines is carried out at least every six months.
During operation collector and synchronous motors, special attention should be paid to the collector-brush apparatus, to monitor the condition of the brushes and to remove carbon-graphite dust from the collectors and rings. By the way, motors of the SDBM series are equipped with a brushless excitation system.
The influence of operating conditions on the service life of an electric motor has been proven by many methods of assessing failures and breakdowns. Choosing the right engine is the primary way to maintain and extend service life. The operating conditions will not affect in any way if the engine will initially operate, for example, with overload or in a room with a high temperature, and the performance will be for the northern countries, instead of the tropical, and so on.
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