Category Archive for: «Motor»

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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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Few Words About Stepper Motor (Advantages, Disadvantages and Classification)

Introduction A stepper motor is an electromechanical device which converts electrical pulses into discrete mechanical movements. The shaft or spindle of a stepper motor rotates in discrete step increments when electrical command pulses are applied to it in the proper sequence. The motors rotation has several direct relationships to these applied input pulses. The sequence […]

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4 Motor Designs Identified In NEMA MG1

It’s all about performance… Performance requirements for various types of induction motors for use on standard sinewave power supplies are identified in NEMA MG1. Some of these types of motors are suitable for use in variable speed applications, dependent on the type of application. The purpose of this section is to provide guidance on the […]

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Testing and Commissioning Procedure For Motors

Scope Of Motor Testing It should be noted that the scope of motor testing depends upon the motor type and size, this being indicated on the inspection forms. Motor vibration shall be measured in a tri-axial direction, i.e.: Point x axis – side of bearing housing at shaft height Point y axis – top of […]

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Sizing The DOL Motor Starter Parts (Contactor, Fuse, Circuit Breaker and Thermal Overload Relay)

Calculate size of each part of DOL motor starter for the system voltage 415V, 5HP three phase house hold application induction motor, code A, motor efficiency 80%, motor RPM 750, power factor 0.8 and overload relay of starter is put before motor. Basic Calculation of Motor Torque and Current Motor Rated Torque (Full Load Torque) […]

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