Jan 27, 2018

Concept of Single-phase induction motors

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Single-phase induction motors

A three phase motor may be run from a single phase power source. However, it will not self-start. It may be hand started in either direction, comming up to speed in a few seconds. It will only develop 2/3 of the 3-Φ power rating because one winding is not used.

Ultrasonic Level Sensor Application

Ultrasonic Level Sensors and Transmitters

Above ground bulk storage tanks are containers that hold large volumes of liquid and typically

Mind bender:

While brain size in Homo sapiens remained largely unchanged over time, the shape gradually became more rounded until achieving its current form, say scientists

Brain shape evolution in Homo sapiens are shown in this combination image—the 300,000 year-old cranium Jebel Irhoud 1 (L) and present day humans (R)—in this undated handout image released on 24 January, 2018. Photo: Reuters

Nissan brain-to-vehicle technology

Nissan’s brain-to-vehicle technology will enable autonomous cars to learn from the brain

The device will measure brain wave activity, which will then be analysed by autonomous systems. Photo:

15 Best Honeymoon Places In World

Honeymoon Places In World

Being a key ingredient to spice up a relationship, a honeymoon requires an apt amount of intimacy and seclusion to kickstart a newly built bond. Therefore, it

Installing a Load Cell: Best Practices

Best Practice Installation

Each load cell installation is unique. Consult a structural engineer when your application requires very high accuracy, long-term stability, custom specifications, or when using in a varied R&D environment. In order to gain precise weighing results, be sure to use specified load applications for load cells. Load cells have a specified load direction; do not apply side forces, bending or torsional movements on load cells. Inappropriate loading applications will risk reducing the life of load cells, plus distortion of correct measurement results.

Types of Relays: Mechanical, SSR, Internal or External

Types of Relays

What are Relays?

Relays are the control switches that operate with low-powered electrical signals controlling most types of circuits. An example of an ideal relay application is having one electrical signal setup to control several circuits, allowing complete isolation of electricity between the controller and the controlled circuits.

Technology Overview

Imagine a product being moved on a conveyor belt that somehow gets out of place. Not having a limit switch at the edge of the belt to stop the process could cause damage to the product and equipment or pose a safety hazard to the operator and facility. That is the risk for machine control systems with moving mechanical parts. We will discuss different types of limit switches and how they are critical components that serve many purposes including safety and mechanical.

5 tech trends

Calculating Power Factor

The angle of this "power triangle" graphically indicates the ratio between the amount of dissipated (or consumed) power and the amount of absorbed/returned power. It also happens to be the same angle as that of the circuit's impedance in polar form. When expressed as a fraction, this ratio between true power and apparent power is called the power factor for this circuit. Because true power and apparent power form the adjacent and hypotenuse sides of a right triangle, respectively, the power factor ratio is also equal to the cosine of that phase angle. Using values from the last example circuit:

Circuits and the speed of light

Suppose we had a simple one-battery, one-lamp circuit controlled by a switch. When the switch is closed, the lamp immediately lights. When the switch is opened, the lamp immediately darkens:

Beat The Heat

With the temperature in Mumbai soaring higher each day, one of the best ways to escape the heat is to visit the hill stations around the city. Moreover, these places can be covered over a weekend (preferably a long one), thus saving you precious leaves! All these hill stations are accessible by road, with cabs being easily available and the roads being very scenic. So here’s presenting a list of some of the most-loved hill stations around Mumbai:

Transmission line- 50-Ohm Cable- Part-A

I came across a length of coaxial cable with the label "50 ohms" printed along its outer sheath. Now, coaxial cable is a two-conductor cable made of a single conductor surrounded by a braided wire jacket, with a plastic insulating material separating the two. As such, the outer (braided) conductor completely surrounds the inner (single wire)

Types of specialized motors

1.Shaded pole induction motor

An easy way to provide starting torque to a single phase motor is to embed a shorted turn in each pole at 30^o to 60^oto the main winding. Typically 1/3 of the pole is enclosed by a bare copper strap. These shading coils produce a time lagging damped flux spaced 30^o to 60^o from the main field. This lagging flux with the undamped main component, produces a rotating field with a small torque to start the rotor.

Tesla Polyphase Induction Motors

Introduction

Most AC motors are induction motors. Induction motors are favored due to their ruggedness and simplicity. In fact, 90% of industrial motors are induction motors.

Nikola Tesla conceived the basic principals of the polyphase induction motor in 1883, and had a half horsepower (400 watt) model by 1888. Though he received a million dollars from George Westinghouse for the rights to manufacture this invention, he died penniless.

Selsyn (synchro) motors

Normally, the rotor winding of a wound rotor induction motor are shorted out after starting. During starting, resistance may be placed in series with the rotor winding to limit starting current. If these winding are connected to a common starting resistance, the two rotors will remain synchronized during starting. This is useful for printing presses and draw bridges, where two motors need to be synchronized during starting. Once started, and the rotors are shorted, the synchronizing torque is absent. The higher the resistance during starting, the higher the synchronizing torque for a pair of motors. If the starting resistors are removed, but the rotors still paralleled, there is no starting torque. However there is a substantial synchronizing torque. This is a selsyn, which is an abbreviation for "self synchronous".

AC commutator motors

AC commutator motors, like comparable DC motors, have higher starting torque and higher speed than AC induction motors. The series motor operates well above the synchronous speed of a conventional AC motor. AC commutator motors may be either single-phase or poly-phase. The single-phase AC version suffers a double line frequency torque pulsation, not present in poly-phase motor. Since a commutator motor can operate at much higher speed than an induction motor, it can output more power than a similar size induction motor. However commutator motors are not as maintenance free as induction motors, due to brush and commutator wear.

Technology for Volt & Current: Honeymoon Places In India

Step-up and step-down transformers

Transformers

So far, we've observed simulations of transformers where the primary and secondary winding were of identical inductance, giving approximately equal voltage and current levels in both circuits. Equality of voltage and current between the primary and secondary sides of a transformer, however, is not the norm for all transformers. If the inductance of the two winding are not equal, something interesting happens

CIRCUIT SCHEMATIC SYMBOLS

Older electrical schematics showed connecting wires crossing, while non-connecting wires "jumped" over each other with little half-circle marks. Newer electrical schematics show connecting wires joining with a dot, while non-connecting wires cross with no dot. However, some people still use the older convention of connecting wires crossing with no dot, which may create confusion. For this reason, I opt to use a hybrid convention, with connecting wires unambiguously connected by a dot, and non-connecting wires unambiguously "jumping" over one another with a half-circle mark. While this may be frowned upon by some, it leaves no room for interpretational error: in each case, the intent is clear and unmistakable:

It is very important to keep in mind that the "normal" contact status of a process-actuated switch refers to its status when the process is absent and/or inactive, not "normal" in the sense of process conditions as expected during routine operation. For instance, a normally-closed low-flow detection switch installed on a coolant pipe will be maintained in the actuated state (open) when there is regular coolant flow through the pipe. If the coolant flow stops, the flow switch will go to its "normal" (unactuated) status of closed. A limit switch is one actuated by contact with a moving machine part. An electronic limit switch senses mechanical motion, but does so using light, magnetic fields, or other non-contact means.

Jan 23, 2018

Types of Switches

Switches

In electrical and electronic system, a switch is a device, which can make or break an electrical circuit or we can say that switch is a controlling device, which interrupt the flow of current or direct the flow of current in another direction. Almost all the electrical and electronics systems contain at least one switch, which is used to make the device ON or OFF. In addition, a switch is used to control the circuit operation and user may able to activate or deactivate the whole or certain parts of the connected circuit.

Journey is the Destination

Dan Eldon once said, “Journey is the Destination“. The landscapes that you witness while travelling to your destination gives you as much peace as the destination itself. The memories that you create while riding on the tough roads rests for the lifetime. There is no reason why should not take a road trip with your friends. India has a lot of scenic road trips to offer, but the trail to the Himalayas steals the show for its scenery that changes its mood very frequently. The Chandigarh city lies very closely to the border of Himachal Pradesh and hence it is quite a famous base to begin your journey towards the majestic Himalayan ranges. Here is the list of best road trips to the Himalayas that you can plan from Chandigarh.

Food of Bihar

The historically rich land of Bihar is equally famous for the plethora of delicacies that feature in its cuisine. The scrumptious and exotic Bihari dishes are highly capable of tingling the taste bud of every food connoisseur.

Star-Delta Starter

Introduction:

Most induction motors are started directly on line, but when very large motors are started that way, they cause a disturbance of voltage on the supply lines due to large starting current surges. To limit the starting current surge, large induction motors are started at reduced voltage and then have full supply voltage reconnected when they run up to near rotated speed. Two methods are used for reduction of starting voltage are star delta starting and auto transformer stating.

Diodes and Rectifiers

A diode is an electrical device allowing current to move through it in one direction with far greater ease than in the other. The most common kind of diode in modern circuit design is the semiconductor diode, although other diode technologies exist. Semiconductor diodes are symbolized in schematic diagrams such as Figure below. The term “diode” is customarily reserved for small signal devices, I ≤ 1 A. The term rectifier is used for power devices, I > 1 A.

Vector Groupof Transformer

Introduction:

Three phase transformer consists of three sets of primary windings, one for each phase, and three sets of secondary windings wound on the same iron core. Separate single-phase transformers can be used and externally interconnected to yield the same results as a 3-phase unit.

Parallel Operation of Transformers

Introduction:

§ For supplying a load in excess of the rating of an existing transformer, two or more transformers may be connected in parallel with the existing transformer. The transformers are connected in parallel when load on one of the transformers is more than its capacity. The reliability is increased with parallel operation than to have single larger unit. The cost associated with maintaining the spares is less when two transformers are connected in parallel.

Electrical Interview questions

Q: What is inrush current?

A: Inrush current is the current drawn by a piece of electrically operated equipment when power is first applied. It can occur with AC or DC powered equipment, and can happen even with low supply voltages.

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