Category Archive for: «Motor»

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13 features and advances of using electronic soft starters for a motor starting

Starting characteristic Soft starters serve for a continuous adjustment of the starting characteristic of three-phase asynchronous motors to the requirements of the load by controlling the voltage across the motor and enable for an optimum integration of the drives in process control by means of various complementary functions. While when star-delta starters are used, the […]

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A Few Words About Selecting AC Induction Motors for Cement Plant Applications

Introduction This technical article relies on the great paper written by Barton J. Sauer (Siemens Energy & Automation) which goes into essence of selecting the proper AC motor for cement plant applications. Although motors may appear to be the least complicated component in the specification of cement mill equipment, this article shall try to demonstrate that cement plant […]

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How to measure insulation resistance of a motor

Winding insulation resistance If the motor is not put into operation immediately upon arrival, it is important to protect it against external factors like moisture, high temperature and impurities in order to avoid damage to the insulation. Before the motor is put into operation after a long period of storage, you have to measure the […]

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PLC application for reduced voltage-start motor control

Reduced-voltage-start motor control circuit Figure 1 shown below illustrates the control circuit and wiring diagram of a 65% tapped, autotransformer, reduced-voltage-start motor control circuit. This reduced voltage start minimizes the inrush current at the start of the motor (locked rotor current) to 42% of that at full speed. In this example, the timer must be set to […]

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Motor Starting via Chokes or Resistors

Reducing the voltage and starting current The series-connected chokes (Figure 1) or resistors (Figure 2) reduce the voltage at the motor and hence also the starting current. The starting torque is reduced by around the square of the current. Starting via chokes At rest the motor impedance is small. Most of the supply voltage drops […]

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Physical Structure & Configuration of DC Machines

Two-pole machine Figure 1 depicts a two-pole machine in which the stator poles are constructed in such a way as to project closer to the rotor than to the stator structure. This type of construction is rather common, and poles constructed in this fashion are called salient poles. Note that the rotor could also be […]

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Inspection and test procedures for Rotating Machinery, Synchronous Motors and Generators

Procedures (Index) Visual and Mechanical Inspection Electrical Tests Test Values Visual and Mechanical Tests Electrical Tests Pictures: Electrical machine wired for electrical testing The Electrical Machines Laboratory TABLE 100.10 – Maximum Allowable Vibration Amplitude TABLE 100.12 – US Standard Fasteners 1. Visual and Mechanical Inspection Compare equipment nameplate datawith drawings and specifications. Inspect physical and […]

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Calculating the short-circuit current across the terminals of a synchronous generator

Alternators and motors Calculating the short-circuit current across the terminals of a synchronous generator is very complicated because the internal impedance of the latter varies according to time. When the power gradually increases, the current reduces passing through three characteristic periods: Subtransient (enabling determination of the closing capacity of circuit breakers and electrodynamic contraints), average duration, 10 […]

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Heat as one of the most common cause of motor failure

Service life Heat is the most common cause of motor failure before reaching rated service life. Overheating arises from a number of factors. If a motor is undersized for an application, or if a manager selects a motor with the wrong starting current and torque characteristics, it will operate warmer than its design temperature. Managers […]

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Identity Card of Every Asynchronous Motor

Motor parameters A motor is characterized by different electrical and constructional parameters which identify its correct application field. Hereunder is a short description of the main parameters included in the nameplate rating with simple information about the electrical parameters which are the most known ones and those more easily explained, whereas particular attention is paid […]

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