Pressure Transducers - What Are they and What do they Do?

When ensuring complete safety in the home and in the workplace, it is important that you make sure you have the right tools for the job. While larger defects can only be effectively repaired by professional contractors, having first class equipment that is designed to register and alert the property owner to any irregularities or deformities is extremely useful, as it allows homeowners to act quickly if anything occurs.

With electrical equipment, gas, water and other such features of a modern home, if something goes wrong, the repair process can often be time consuming and expensive. By putting in place certain safety measures, you are able to receive early warnings of an electrical or heating failure, which you can then take into account and make the necessary repairs. A pressure transducer is one such piece of equipment.

What are pressure transducers?

In short, pressure transducers are designed to convert pressure of all types into analog, electrical signals so that they can be easily measured and monitored. They come in a variety of different styles and sizes with different purposes depending on the type of transducer. They are often rather simple in appearance, with a tube-like or circular stainless body with a wire or cable on one side and a pipe connector on the other.

Uses of pressure transducers

Pressure transducers are used for things such as the monitoring of air quality in a certain space, environmental enclosures, dust collecting systems, leak detection and much more. They can be used anywhere where important gauge pressure measurements are required. When choosing the best transducer for your purposes, it is essential that you determine the situation where the transducer is going to be used and ask for professional advice on choosing the ideal transducer. Some transducers, or sensors, are better acquainted with working in extreme environments, whereas others are not suitable for such measures. It is important to know the difference between each type of transducer.

The Importance of ensuring a working Pressure Transducer is installed

If a pressure transducer is not working properly, it will not be able to make accurate measurements and that is where things can start to go wrong. For example if your pressure transducer is designed to measure the gas and oil pressure of a product, and it is faulty or not installed properly, you have no way of knowing whether or not the product is also faulty or whether it is working fine. For some appliances, this can be dangerous, as they could be leaking gas or oil and you have no way of knowing. In these instances, a first class pressure transducer is essential.

Different Types of Transducer

Some pressure transducer are more equipped to work at high temperature or in extreme conditions, in order to provide an accurate measurement in otherwise unsafe environments. There are a wide range of different transducers that are all suited to the specific appliance, so when you’re looking at buying a transducer, make sure the one you select is suitable for the product you’re using it with.

At the end of the day, it is important to know how crucial pressure transducers are to certain pieces of equipment, but a lack of knowledge in this area is not necessarily dangerous. By asking a professional for advice and assistance in choosing a good pressure transducer, or by asking for advice on the maintenance and repair of certain appliances, you can make sure that you make the best purchase for your home or office environment. There are those who are specifically qualified to perform the installation for you, so it may be a good idea to look into these options if you think it necessary.

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Article provided by App Eng, an application engineering company based in South East England for over 30 years.

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Causes of Low Power Factor and it's Correction (PF improvement)

We've already seen what power factor is and what the disadvantages are if it is low. Ideally, power factor should be unity (1). For practical purposes, it should be as close to unity as possible. If it is low, the operation is uneconomical. First we shall learn what causes the power factor (pf) to be low.

Causes of low Power Factor

Inductive Loads

• 90% of the industrial load consists of Induction Machines (1-ϕ and 3-ϕ). Such machines draw magnetizing current to produce the magnetic field and hence work at low power factor.
• For Induction motors, the pf is usually extremely low (0.2 - 0.3) at light loading conditions and it is 0.8 to 0.9 at full load.
• The current drawn by inductive loads is lagging and results in low pf.
• Other inductive machines such as transformers, generators, arc lamps, electric furnaces etc work at low pf too.

Variations in power system loading

• Today we have interconnected power systems. According to different seasons and time, the loading conditions of the power system vary. There are peak as well as low load periods.
• When the system is loaded lightly, the voltage increases and the current drawn by the machines also increases. This results in low power factor.

Harmonic currents

• The presence of harmonic currents in the system also reduces the power factor.
• In some cases, due to improper wiring or electrical accidents, a condition known as 3-ϕ power imbalance occurs. This results in low power factor too.

Power Factor Correction

As discussed above, low power factor is mainly due to lagging currents drawn by inductive loads. Before we study the schemes for Power Factor Correction (PFC), note the following points:

• For pure inductance, current lags behind voltage by 90°.
• For pure capacitance, current leads voltage by 90°.
• So, the solution is simple. If we use capacitors to draw leading current, we can cancel the effects of lagging inductive current and hence improve the power factor.

The above fig shows a common circuit. The R and L are present in all inductive equipments and the C is used for pf improvement.
Here, IL = current drawn by the circuit capacitor C isn't used,
         ϕL = phase angle between voltage V and load current IL,
         IC = capacitive current drawn by C,
          I = resultant current when C is used,
          ϕ = phase angle between voltage V and net current I.

• As shown in the above phasor diagram, ϕ < ϕL
• Therefore cos ϕ > cos ϕL, hence power factor is improved

Based upon this principle, following methods are used for power factor correction (PFC).

Methods of Power Factor Correction or Improvement

1. Capacitor bank

• Simplest method.
• applied at areas where large inductive loads (lagging currents) are present.
• Static capacitors are used which produce capacitive reactance that cancels out the inductive reactance of the lagging current.
• These banks can be star connected or delta connected.
• A control system is usually provided which monitors the pf and switches the capacitors ON or OFF.

Advantages of using capacitor banks for PF correction

• low losses
• low maintenance
• light weight
• easy to install
• no foundation required

Disadvantages

• short life (8-10 years)
• capacitors can get easily damaged due to over voltage
• once damaged, the repair is costly and uneconomic
• due to constant switching, switching surges and harmonics may be produced

2. Synchronous condenser

• When a synchronous motor is over excited, it draws leading current. In a way, it behaves like a capacitor.
• When such a motor is over excited and run at no load, it is called a Synchronous Condenser.
• The most attractive feature is that it allows stepless pf correction. In a static capacitor, the leading kVAR supplied are constant. But in a synchronous condenser, we can vary the field excitation and hence control the amount of capacitive reactance produced.
• Synchronous Condensers are used in large factories, industries and major supply substations.

Advantages

• longer lifespan (almost 25 years)
• flexible and stepless control of pf
• reliable
• does not get affected by harmonics
• No switching is required hence harmonics are not produced

Disadvantages

• higher losses
• expensive
• higher maintenance costs
• produces noise
• Synchronous motor is not self starting, so auxiliary device is needed.
• uneconomical for equipment below 500 kVA

3. Phase advancer

• Can be used only for Induction Motors
• We know that stator winding draws lagging current in a motor. This current is drawn from the main supply.
• Hence, to improve pf, we supply this lagging current from an alternative source. This alternative source is the phase advancer.
• A phase advancer is basically an AC exciter. It is mounted on the same shaft as the main motor and connected in the rotor circuit. It supplies exciting ampere turns to the rotor circuit at slip frequency. This improves the power factor.
• Another attractive feature is that if we supply more amp-turns than needed, the motor will operate in an over excited state (at leading pf).

Advantages

• Lagging kVAR drawn by the motor are reduced because the exciting ampere turns are supplied at slip frequency.
• Can be utilized easily where synchronous motor is inadmissible

Disadvantages

• Uneconomical for motors below 200 HP (150 kW)

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Author: Manoj Arora is an electrical engineering student and a writer from Gujarat, India. He writes poems and short stories whenever he's not immersed in a book.
Credits for the Graphics: Kiran Daware.

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Understanding the Power Factor

Energy is needed and utilized everywhere in the world. From the point of view of convenience, efficiency and economy, it is best that we generate, transmit and distribute it in electrical form before it is converted into the required one by suitable equipments. For the same reasons of economy and efficiency, we use AC rather than DC. Practically, we generate, transmit and distribute energy in AC form almost exclusively. DC is used either in DC applications (DC machines and electronic circuits) or in HVDC transmission links.

Wherever AC power is utilized, the question of power factor arises itself.

Power Factor

• Defined as 'the cosine of the angle between the voltage and current'.
• In AC circuit, the voltage and current are ideally in phase.
• But practically, there exists a phase difference between them.
• The cosine of this phase difference is termed as power factor.
• It can be defined and mathematically represented as follows:

From the fig. (a) above, it can be clearly noted that there is a phase difference of angle ɸ between the voltage phasor and the current phasor.
Power Factor = cosɸ

The fig. (b) is called as Power Triangle
Here, VI sinɸ = Reactive power (in VAR)
          VI cosɸ = Active power (in Watts)
          VI = Apparent power (in VA)
PF = cosɸ = Active Power (W) / Apparent Power (VA)

The fig. (c) is called as Impedance Triangle
Here, R = Resistance, X = Reactance, Z = Impedance
Z² = R² + X²
PF = cosɸ = R/Z

The Power Factor can be lagging, leading or unity.

Lagging Power Factor

• When current lags behind the voltage, the power factor of the circuit is called 'Lagging'
• When the circuit is inductive, the pf is lagging.
• The loads such as induction motors, coils, lamps, etc are inductive and have Lagging pf.

Leading Power Factor

• When current leads the voltage (or voltage lags behind the current), the power factor of the circuit is called 'Leading'.
• When the circuit is capacitive, the pf is leading.
• Capacitive loads such as Synchronous condensers, capacitor banks etc draw leading current. Such circuits have leading power factor.

Unity Power Factor

• Power factor is unity (i.e. 1) for ideal circuits.
• When current and voltage are in phase, PF = 1
• Power factor cannot be more than unity.
• Practically, it should be as close to unity as possible.

If power factor is low, following problems are encountered:

Effects of low power factor

1. Load Current
   Power in an AC circuit can be given as: P = VI cosɸ
   Therefore, cosɸ = P / VI
   I ∝ 1 / cosɸ
   Similar relationship can be derived for 3 phase circuit too. We can see that current is inversely proportional to pf.
   
   For example, consider that we want to transfer 10 kVA power at 100 V
   If PF = 1,
   I = P / (V cosɸ) = 10000 / (100 x 1) = 100 A
   If PF = 0.8,
   I = P / (V cosɸ) = 10000 / (100 x 0.8) = 125 A
   Hence, the current drawn is higher for low power factor.
2. Losses: As stated above, for low pf, the current drawn is high. Hence copper losses (I²R losses) will also be high. This decreases the efficiency of the equipment.
3. Overheating of the equipment: I²R losses produce heat (Joule's law). Hence, the temperature rise will be relatively more for low PF which will further increase the stress on the insulation.
4. Size of conductor: Low power factor causes higher load current. If the load current increases, the size of the conductor required will also increase. This will further increase the conductor cost.
5. kVA rating of the machine: Machines are not rated in kW while manufacturing because the power factor of supply is unknown. Instead, they are rated in kVA.
   According to definition, Cosɸ = Active power (kW) / Apparent power (kVA)
   Hence, kVA rating = 1 / cosɸ
   Therefore, for low pf, equipment of larger kVA rating is needed. But larger kVA rating means larger size of the equipments. If size increases, the cost also increases.
6. Voltage Regulation: It is defined as the difference between sending and receiving end voltage per unit sending end voltage. When power is transferred from one end to another, the voltage drops due to several reasons. This voltage drop should be within permissible limits.
   P = VI cosɸ , Therefore I ∝ 1 / V
   For low power factor, current will be more and hence voltage drop will be increased. Hence, the voltage regulation at low power factor is poor.
7. Active and Reactive power (Power Transfer Capacity): Active and reactive power both are transferred over the line together. Active power is needed for supplying the load. Reactive power is needed to maintain the voltage of the line. But if reactive power is more, then active power transferred is decreased. For low pf, active power is low because, cosɸ = Active power (W) / Apparent power (VA). This results in uneconomic operation.

These are the results of low power factor. For optimum performance, the power factor should be as close to unity as possible. To achieve this, power factor correction equipments are used.

[Also read: Comparison of Various Power Plants]

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Author: Manoj Arora is an electrical engineering student and a writer from Gujarat, India. He writes poems and short stories whenever he's not immersed in a book.
Credits for the Graphics: Kiran Daware.

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Why Toroidal Transformer Became a Globally Well-Known Product

Industry experts say that toroidal transformers are small in size and are typically used when there is a need for a transformer that offers low magnetic resistance. So, if you are looking for a transformer that will provide you value for money from the beginning till the end of its life cycle, try considering a toroidal transformer for your application.

Why Should You Use a Toroidal Transformer?

Below find a list detailing the important advantages of a toroidal transformer in comparison to a conventional transformer.

• Low Weight & Small Size
  Toroidal transformer manufacturers keep certain things in mind and design a unique configuration which provides maximum containment of magnetic fields without interrupting overall efficiency. The toroidal transformer core is created with a minimum raw material. The weight and size of this transformer are affected due to high packing density. As per the power rating, one can reach up to 50% weight reduction.
• Mounting Ease
  Toroidal transformers can be mounted easily using just a screw due to which the assembly time gets reduced significantly. This even reduces maintenance, repair and replacement-related down time. One can even use different mounting options like using enclosures or capsuling in a plastic container.
• Special Customized Core Designs Possible
  If the standard size of a toroidal transformer doesn’t fit in your application, you can vary the core dimensions with ease. You can have an extreme flat transformer design for your low profile equipment.
• Very Low Magnetic Interference Field
  If we speak of conventional transformers, they are mostly constructed using two individual core parts. Joining these parts result in small air gaps due to which magnetic stray field arises. Whereas, in the toroidal transformer, there is no such air gap, so these emit a very low magnetic interference field. This property makes it useful in critical applications like audio electronics and medical equipment.
• Very Low Mechanical Hum
  The core of a conventional transformer is formed by two individual parts of stacked silicon steel sheets. All these parts have loose sheet ends which cause the transformer to vibrate resulting in producing disturbing hum. On the other hand, the core of a toroidal transformer is made up from a long strip of silicon steel which is tightly wound to give it a toroidal shape. Consequently, it results in a virtually hum-less transformer.
• Low Magnetizing Current
  A toroidal transformer sees very less iron losses which makes the magnetizing current much lower than a conventional transformer. Ultimately, this makes a toroidal transformer very efficient.
• Low Operating Temperature
  If we compare the operations and specifications of a toroidal transformer with a similar conventional one, we will realize that they ensure low operating temperatures.
• High ROI
  Given the benefits that these toroidal transformers offer, one can have complete value for money.

[ Also read: Auto Transformer ]
Toroidal transformers, thus can be incorporated and customized with features benefitting your application. You will see lesser downtime and a higher return on investment which makes it a popular choice in several applications.

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Author: Dani Kate is a content strategist and online blogger with vast background knowledge of mechanical engineering. She is interested in exploring the industrial and mechanical niche. She likes to explain the complex theories of the industry in simple terms for better understanding of the readers.

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Comparison of Various Power Plants

Modern society cannot function without a reliable power system. We need energy for all our activities, and we utilize this energy in various forms such as thermal, electrical, mechanical etc. However, electrical energy can be considered as the most important of these since we can generate, transmit, distribute, convert and utilize it efficiently and economically.

The generation aspect is at the foremost of the chain and it is realized with the help of power plants. A set of equipments utilized to produce electrical power in large quantities (usually hundreds - thousands of MW) is called a generating station or a power plant. Such a power plant will convert one form of energy (nuclear, thermal, hydro, solar etc.) to electrical energy.

On the basis of this form of energy conversion, power plants are broadly classified as follows:

1. Thermal Power Station (Steam power plant)
2. Hydroelectric Power Station
3. Nuclear Power Station

There are other plants too, such as:

• Solar Power Plant
• Wind Power Plant
• Tidal Power Plant
• Geothermal Power Plant
• Diesel Power Plant

However, they represent only a small part of the global scheme in terms of capacity and utilization.

Each of these power plants has its own set of features, requirements, advantages and disadvantages. They can be compared on the basis of several parameters. The salient points are given below:

Thermal Power Station

Principle of operation: It works on Modified Rankine Cycle.

Location: It is located at a site where coal, water and transportation facilities are available easily. It is located near load centers.

Requirement of Space: Need a large space due to coal storage, turbine, boiler and other auxiliaries.

Efficiency: Overall efficiency is least compared to other plants. (30%-32%)

Fuel Used: Coal (mostly) or oil.

Availability of Fuel: Coal reserves are present all over the world. However, coal is non-renewable and limited.

Cost of Fuel: High. Coal is heavy and has to be transported to the plant.

Initial Cost of Plant: Lower than Hydroelectric and Nuclear power plants.

Running Costs: Higher than Hydroelectric and Nuclear power plants.

Maintenance Costs: High. Skilled engineers and staff are needed.

Transmission and Distribution Cost: Low. It is usually located near load centers.

Start-up Power: About 10% of unit capacity.

Starting time: Large

Standby Losses: More than hydroelectric and nuclear power plants. Boiler flame has to be kept burning, so some amount of coal is used constantly, even when the turbine is not in operation.

Cleanliness: Less clean. Smoke and ash are produced.

Environmental Considerations: Air pollution occurs and leads to acid rain. Greenhouse gases are also produced.

Life Time: 30 - 40 years.

Hydroelectric Power Plant

Principle of operation: Potential energy of water is converted to Kinetic energy and used to rotate a turbine.

Location: Located where a large amount of water can be collected easily in a reservoir by constructing a dam. Usually in a hilly area at high altitude.

Requirement of Space: Very large space required. A dam is huge.

Efficiency: As high as 85% to 90%

Fuel Used: Water

Availability of Fuel: Availability of water is unreliable because it depends on the weather (rainfall.)

Cost of Fuel: Water is free.

Initial Cost of Plant: Very high. Construction of a dam and reservoir is expensive.

Running Costs: Zero, because no fuel is needed.

Maintenance Costs: Low.

Transmission and Distribution Cost: High. It is located in remote areas, away from load centers.

Start-up Power: 0.5% to 1% of unit capacity.

Starting time: Low. Can be started instantly.

Standby Losses: None.

Cleanliness: Clean.

Environmental Considerations: Affects marine life. People in the region have to be relocated.

Life Time: Large (50 to 100 years.)

Nuclear Power Plant

Principle of operation: Thermonuclear fission.

Location: Located away from heavily populated areas.

Requirement of Space: Requires minimum space compared to other plants of the same capacity.

Efficiency: Higher than Thermal Power Station. About 55%

Fuel Used: Uranium (U235) and other radioactive metals.

Availability of Fuel: Deposits of nuclear fuel are present all over the world. Also, uranium can be extracted from sea water, but it’s a complicated and complex process.

Cost of Fuel: Fuel (uranium) itself isn’t too costly. However, if enriched uranium is used, then the cost of fuel increases considerably. A small amount of fuel is used, so transportation costs are less.

Initial Cost of Plant: Highest. A nuclear reactor is complex and requires the most skilled engineers.

Running Costs: Small amount of fuel used, so running cost is low.

Maintenance Costs: Very high. Skilled personnel are needed.

Transmission and Distribution Cost: Quite low. Such plants can be located near the load centers.

Start-up Power: 7% to 10% of unit capacity.

Starting time: Less than TPS. Can be started easily.

Standby Losses: Less.

Cleanliness: Radioactive waste is produced. Less clean than HPS.

Environmental Considerations: Disposal of radioactive wastes may affect the environment, especially if it is buried underground. Underwater contamination may occur.

Life Time: 40-60 years.

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Author: Manoj Arora is an electrical engineering student and a writer from Gujarat, India. He writes poems and short stories whenever he's not immersed in a book.

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