What affects the life of the electric motor and how to extend it
Electric motors of both alternating and direct currents are designed for a service life of 15-20 years (as a rule). Subject to the rules of operation and timely maintenance, electric machines last longer than this period. In the article we will tell the readers of the site Elecroexpert, which affects the life of the electric motor and how it can be extended.
Rules for choosing an electric motor
In order for the standard service life not to decrease during the operation of the engine, it is necessary to initially 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 motor. In this case, it must be taken into account that the electric machine will heat up under load, and the air temperature will increase accordingly.
- The power of the electric motor should be higher by 10% of the power of consumers (we are talking about the load capacity, power and torque necessary to drive the actuators in motion). In accordance with GOST, when designing an electric power system, the electric motor power is taken with a margin of 10% of the nominal.
- The choice of explosion and moisture and dust protection (according to the standard IP) The engine must comply with the operating conditions of the machine. Degrees of protection, types of performance and categories of electrical equipment are regulated by GOST R IEC 60034-5-2007.
- The choice type of electric motorsynchronous or asynchronous, must correspond to the nature of the load and the mode of use (long, short, intermittent and others). With the wrong choice of engine to the mechanism, its service life is significantly reduced. So do not use the engine from a winch, crane or valve actuator to drive fans or pumps.
- The voltage and current of the electric motor must be selected taking into account the possibility of power supply to the enterprise. To reduce inrush currents (especially for high-power EDs), it is worth choosing an electric machine with start-up by switching with"Stars" to the "triangle". For this, the nominal voltage of the "triangle" should be equal to the linear 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 the work and affect the service life. This is the moment of load on the shaft and energy efficiency, and many others.
The manufacturer attaches instructions to each product. Throughout the 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 contentious issues, you can make a request to the manufacturer.
In operation, throughout the entire service life, the electric motor needs daily, weekly or at other intervals monitoring and inspection:
- winding insulation resistance measurement rotor and stator (also carried out before each launch);
- measuring the temperature of the windings (at rated load);
- bearing temperature control (organoleptic method is allowed);
- control engine vibration and 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 necessary to control the humidity in the room, moisture from the air can condense in the electric motor due to temperature differences, which will lead to a decrease in insulation resistance and increased heating of the windings. Electric motor bearings can also suffer from condensation, especially after long periods of inactivity.
One of the most common causes of failure of an electric motor is the quality of electricity. The quality of electricity is determined GOST 32144-2013. When the supply voltage decreases, the stator current increases and, accordingly, the windings heat up. Heating the windings significantly reduces the life of the insulation.
Due to the increased voltage there is an increase in the magnetic flux of the stator, the magnetization current, which leads to heating of the core. Temperatures reach critical levels, right up to the fire of steel. In addition, due to the increased supply voltage, reactive power is taken from the network, which negatively affects consumers.
Maintenance should be carried out in time and in the volumes specified in the instruction manual. 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 service life of the engine will exceed that specified in the data sheet.
With electrical installations up to 100 kW, as a rule, three-phase asynchronous motors with a squirrel-cage rotor are chosen. This is due to the simplicity of design, ease of maintenance and use in work, high reliability and low cost. Maintenance of such engines is carried out at least once every six months.
During operation collector and synchronous engines, 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, the SDBM series motors are equipped with a brushless excitation system.
The influence of operating conditions on the life of the electric motor is proven by many methods for assessing failures and breakdowns. Choosing the right engine is the primary way to maintain and extend your life. The working conditions will not affect in any way if initially the engine will work, for example, with overload or in a room with a high temperature, and the execution will be for northern countries, instead of tropical and so on.