Choice of electric motors

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Section 5. Electric power plants

Electric motors and their switching devices. Choice of electric motors

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Encyclopedia of radio electronics and electrical engineering / Rules for the installation of electrical installations (PUE)

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5.3.9. The electrical and mechanical parameters of electric motors (rated power, voltage, speed, relative duration of the operating period, starting, minimum, maximum torques, speed control limits, etc.) must correspond to the parameters of the mechanisms they drive in all modes of their operation in this installation .

5.3.10. For mechanisms, the preservation of which in operation after short-term interruptions in power supply or a decrease in voltage due to a short-circuit disconnection, the action of an automatic reclosure or AVR, is necessary according to technological conditions and is permissible according to safety conditions, self-starting of their electric motors must be ensured.

As a rule, it is not required to use electric motors and transformers of greater power for self-starting mechanisms than is required for their normal long-term operation.

5.3.11. To drive mechanisms that do not require speed control, regardless of their power, it is recommended to use synchronous or asynchronous electric motors with a squirrel-cage rotor.

To drive mechanisms that have difficult starting or operating conditions or require a change in speed, electric motors with the simplest and most economical methods of starting or speed control possible in this installation should be used.

5.3.12. Synchronous motors, as a rule, must have devices for forcing excitation or compounding.

5.3.13. Synchronous electric motors, in cases where they can provide voltage regulation or reactive power mode in a given load node, should have ACD in accordance with 3.3.39.

5.3.14. DC motors are allowed to be used only in cases where AC motors do not provide the required characteristics of the mechanism or are uneconomical.

5.3.15. Motors installed in normal environments must generally be IP00 or IP20.

5.3.16. Electric motors installed outdoors must have a design of at least IP44 or a special one corresponding to the conditions of their operation (for example, for open chemical installations, for especially low temperatures).

5.3.17. Electric motors installed in rooms where dust and other substances that interfere with natural cooling are possible to settle on their windings must have a design of at least IP44 or purged with a supply of clean air. The body of the blown electric motor, air ducts and all interfaces and joints must be carefully sealed to prevent air from being sucked into the ventilation system.

In the case of a ventilated version of the motor, it is recommended to provide dampers to prevent the intake of ambient air when the motor is stopped. Heating of external (cold) air is not required.

5.3.18. Electric motors installed in damp or especially damp places must have a design of at least IP43 and insulation designed for moisture and dust (with special coating, moisture resistant, etc.).

5.3.19. Electric motors installed in places with chemically active vapors or gases must have a design of at least IP44 or purged with a clean air supply, subject to the requirements given in 5.3.17. It is also allowed to use electric motors of performance not less than IP33, but with chemically resistant insulation and with closing of open non-insulated current-carrying parts with caps or in another way.

5.3.20. For electric motors installed in rooms with an air temperature of more than plus 40 ºС, measures must be taken to exclude the possibility of their unacceptable heating (for example, forced ventilation with a cooling air supply, external airflow, etc.).

5.3.21. With a closed forced ventilation system for electric motors, devices for monitoring the temperature of air and cooling water should be provided.

5.3.22. Electric motors equipped with thermal indicators embedded in the windings or magnetic cores must have leads from the latter to special shields that ensure the convenience of periodic measurements. Panel meters for this, as a rule, should not be provided.

See other articles Section Rules for the installation of electrical installations (PUE).

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