Makunawa Elektrikin

Ma'ana da Turancin Tachometers

Ma'ana

Tachometer shine wurar tafi masu amfani da ita don bincike tsari ko kiyasin harkokin mutanen wataki da ya gudana. Yadda ake amfani da ita ta shahara da matsalolin yawan harkokin bayan dabbobi da watakan abin da ya gudana. Idan watakai ya harko, wannan matsalolin ya ba da tasirin electromotive (EMF) a kofin da aka gada a bayanan dabbobi mai zafi. Tsarin EMF na biyu ta shahara da tsari na harkokin watakai, wanda ya ba da kyau ga binciken tsari na harkokin abin.

Turancin Tachometers

Tachometers zai iya kanza a cikin duwannin biyu: mechanical da electrical.

• Mechanical Tachometer: Wannan turanci na tachometer ta bincike tsari na harkokin watakai a cikin minutes per revolution (RPM). Ya ba da alama na mechanical da ya nuna tsari na harkokin watakai, yawanci da amfani da linkage da pointer a dial mai sakamakon.

• Electrical Tachometer: Electrical tachometer ya faruwa kiyas na harkokin watakai zuwa voltage na electric. Daga mechanical tachometers, electrical tachometers suna da fa'idota kamar ingantaccen rarrabe, amfani da electronic control systems da kuma amfani da bayyana muhimmin bayanai game da duk lokaci. Saboda haka, suna da amfani a cikin binciken tsari na harkokin shafts. A cikin nature na voltage na biyu, electrical tachometers zai iya kanza a cikin subtypes biyu:

• AC Tachometer Generator

• DC Tachometer Generator

DC Tachometer Generator

DC tachometer generator an samun mafi girman kompontents: permanent magnet, armature, commutator, brushes, variable resistor, da moving - coil voltmeter. Don bincike tsari na harkokin abin, an guda shaft na abin da DC tachometer generator.

Principle na yi aiki na DC tachometer generator ta shahara da electromagnetic induction. Idan conductor mai sarrafa ya harko a cikin dabbobi, EMF ta faru a cikin conductor. Tsarin EMF na biyu ta shahara da biyu: amount of magnetic flux linked with the conductor da kuma tsari na harkokin watakai. Idan watakai ya harko, armature a cikin DC tachometer generator ya harko a cikin dabbobi na permanent magnet, wanda ya faruwa EMF da ta shahara da tsari na harkokin watakai. Wannan EMF ta zama DC voltage da commutator da brushes, wanda zai iya bincika da moving - coil voltmeter ko kuma process da electronic circuits don amfani da su.

Aiki da Iyakoki na DC Tachometer Generator

A cikin DC tachometer generator, armature ya harko a cikin dabbobi na permanent magnet. Idan armature ya harko, electromagnetic induction ta faru, wanda ta faruwa EMF a cikin coils da aka wind around it. Tsarin EMF na biyu ta shahara da tsari na harkokin watakai; idan watakai ya harko ne, EMF na biyu ya zama daɗi.

Commutator, tare da brushes, ana da muhimmanci a aikin generator. An yi conversion na alternating current (AC) a cikin armature coils zuwa direct current (DC). Wannan conversion ta shahara don binciken signal na electric. Moving - coil voltmeter an amfani da ita don bincike EMF, wanda ya ba da output da ta nuna tsari na harkokin watakai.

Polarity na induced voltage ta ba da muhimmiyar bayanai. Ta nuna direction na harkokin watakai. Misali, polarity mai positive zai nuna harkokin clockwise, sannan polarity mai negative zai nuna harkokin counterclockwise. Don haƙar da voltmeter da kuma binciken accurate, an gude resistance a series with it. Wannan resistor ta rage flow na high - current generated by the armature, wanda ya haƙar da damage to the measuring device and maintaining the integrity of the measurement process.

EMF na biyu a cikin DC tachometer generator zai iya nufin da formula:

Where, E – generated voltage
Φ – flux per poles in Weber
P- number of poles
N – speed in revolution per minutes
Z – the number of the conductor in armature windings.
a – number of the parallel path in the armature windings.

Advantages and Disadvantages of DC Tachometer Generator and Introduction to AC Tachometer Generator
Advantages of the DC Tachometer Generator

DC tachometer generator an ba da fa'idota kamar yadda ake bayyana a nan:

• Indication of Shaft Rotation Direction: Polarity na induced voltages ta nuna direction na rotation na watakai. Wannan feature ta ba da muhimmiyar bayanai game da rotational dynamics na machine, wanda ya haƙar da operators don monitor and control the system more effectively.

• Use of Conventional Voltmeter: Conventional DC type voltmeter an amfani da ita don bincike induced voltage. Wannan simplicity in measurement equipment ta rage complexity and cost associated with setting up the measurement system, making it accessible and easy to use for a wide range of applications.

Disadvantages of the DC Tachometer Generator

Duk da fa'idota, DC tachometer generator na da kungiyoyi da za a duba:

• Maintenance Requirements: Commutator and brushes, which are essential components for converting the alternating current generated in the armature into direct current, require periodic maintenance. Over time, these components can experience wear and tear due to mechanical friction and electrical arcing, leading to reduced performance and potential failures if not properly maintained.

• Output and Input Resistance Issues: The output resistance of the DC tachometer is typically higher compared to its input resistance. In situations where a large current is induced in the armature conductor, this can cause distortion of the constant magnetic field of the permanent magnet. Such distortion can lead to inaccuracies in the measurement of the induced emf and, consequently, errors in determining the rotational speed of the shaft.

AC Tachometer Generator

Reliance na DC tachometer generator on commutators and brushes gives rise to several limitations. To address these issues, the AC tachometer generator was developed. An AC tachometer generator features a stationary armature and a rotating magnetic field. This design eliminates the need for commutators and brushes, thereby overcoming many of the maintenance and performance problems associated with DC tachometers.

As the rotating magnetic field interacts with the stationary coils of the stator, an electromotive force (EMF) is induced. Both the amplitude and frequency of the induced emf are directly related to the speed of the shaft. This relationship allows for the measurement of angular velocity by either analyzing the amplitude or the frequency of the induced electrical signal.

The following circuit is utilized to measure the speed of the rotor by focusing on the amplitude of the induced voltage. First, the induced voltages are rectified to convert them from alternating current to direct current. Subsequently, the rectified voltages are passed through a capacitor filter, which effectively smoothens out the ripples in the rectified voltage waveform, providing a more stable and accurate measurement of the induced voltage amplitude related to the shaft's rotational speed.

Drag Cup Rotor AC Generator
The drag cup type A.C tachometer is shown in the figure below.

• Structure and Characteristics of AC Tachometer Generator
  The stator of the AC tachometer generator is equipped with two distinct windings: the reference winding and the quadrature winding. These windings are positioned at a 90 - degree angle to each other, which is a key aspect of the generator's design for accurate operation. The rotor of the tachometer is crafted from a thin aluminium cup and is situated within the field structure.
  Constructed from a highly inductive material, the rotor exhibits low inertia, enabling it to respond quickly to changes in rotational speed. An electrical input is supplied to the reference winding, while the output signal is retrieved from the quadrature winding. As the rotor rotates within the magnetic field, it induces a voltage in the sensing (quadrature) winding. The magnitude of this induced voltage is directly proportional to the rotational speed of the rotor, establishing a reliable mechanism for measuring angular velocity.
  Advantages
  Ripple - Free Output: The drag cup tachogenerator is notable for producing an output voltage that is free from ripples. This smooth output ensures more accurate and consistent speed measurements, making it well - suited for applications where precise speed monitoring is crucial.
  Cost - Effective: Another significant benefit is its relatively low cost. This affordability makes the drag cup tachogenerator an attractive option for a wide range of applications, especially those where cost - effectiveness is a priority without sacrificing basic functionality.
  Disadvantage
  However, the drag cup tachogenerator has a notable limitation. When the rotor spins at high speeds, a nonlinear relationship emerges between the output voltage and the input speed. This nonlinearity can lead to inaccuracies in speed measurement if not properly accounted for, potentially restricting the generator's use in scenarios that require high - speed and highly precise rotational speed measurements.