Star/Delta Connections – Used for the 3-Phase Motors

There are two ways to connect a 3-phase electrical motor. The first one is the star which is denoted in Y and the next one is delta that is denoted in A. Well, there are also some winding phases associated with a 3-phase electrical motor and they can be denotes as U, V as well as W and series of them can be presented in this format U1-U2, V1-V2, as well as W1-W2. In case of the Y or star connection, the winding phases of the same motor can be joined together in order to form the zero point and this mostly looks like the star Y.

Star connection of motor

For example, on a motor plate this value is 690/400 V. In this case, star connection can produce higher voltage and the delta shows the low level of voltage. Well, the current that can be mentioned on motor plate can even show the lower value for star connection as well as higher value for delta connection.  As per this rule, the main supply connection to the 3-Phase motor can have the terminals which are marked like U, V as well as W. And at the same time, phase sequence can be marked as L1, L2 as well as L3. This suggests the 3-phase motor will start rotating clockwise from drive end that is marked as D.

Delta connection on electrical motor

If you wish to make the 3-phase motor rotate in an anti clockwise motion, then 2 from the 3 conductors attached to the motor or the starter can be switched. To get a better idea about this, you can check the function of a cooling fan and look for it when it rotates in an anti-clockwise motion.
In some cases, the dual starter is taken that connected the terminals of the motor directly to function as per the power supply. In this case, the motor can acquire full flow of voltage due to the power supply. Due to this reason, high starting flow of current can occur through a motor. Well, this sort of starting is just perfect for those motors which are small and their capacity remains below 5 hp. In some cases, the reduced-voltage starter is employed for the motors that are of above 5 hp. The generation of reserve power and the reliability of power supply dictate the real use of the reduced voltage. It also dictates the fact that starting current should not be reduced for the induction motors. However, the voltage flowing for these motors can be reduced to obtain better results.  It can be accomplished through star delta starter, autotransformer starter and resistor starter.

Star-delta connection with loads (coils in motor)

As far as the star delta starters are concerned, these are known as the most usual ones used for reducing the voltage for the 50 hertz world. They are also known as the Wye and Delta starters as per the 60 hertz world. These are basically used in order to reduce the starting current that is applied for the motor during when it starts. This is done to reduce the disturbances that can arise due to the interference in the supply of electricity.

Engineering and Production Management

Being an engineer, especially a mechanical engineer, has a lot of areas and fields to work on. In manufacturing industries and engineering firms, a manager is usually, and often necessary to be an engineer as well, who has not just the managerial skills but also has the knowledge and skills in technical aspects.

Tasks and areas of an engineer manager

As an engineer manager, your job is to both monitor productivity of your workers and at the same time to ensure that the technical conditions of the company are in proper conditions. This job is a combination of being an engineer and a manager or businessman.

As a production engineer, you should be able to perform the following tasks:

• Design or initiate the designing of the whole industrial processes and systems for the production.
• Design and improve the structure of the product as well.
• Keep records on technical data and make those records always updated.
• Analyze technical output and forecast problems that may arise.
• Provide solutions on problems arise.
• Manage and provide proper technical instructions and trainings for the workers that will operate the machines and other working equipments.
• Be updated on latest technology news and issues, and apply new knowledge and techniques as well for the improvement of production.
• Consider the effect of the technology and processes being used on the environment.

Also as an engineer manager, you must have the basic knowledge and background on managerial and business aspects. You must be able to perform the following tasks:

• Management of technology aspects. You should be able to manage the equipments and the workers who will use those as well.
• Negotiate and deal with external stakeholders for business matters of the company.
• Provide schedule for meeting and discuss about the latest technical issues on the company, and the latest news and improvements as well.
• An engineer manager must also be available for consultation. Workers must be able to rely on the engineer manager regarding the processes and the work done on the industry.
• A good engineer manager must also have a basic knowledge on accounting principles, finance, management information systems, and quality control.
• An engineer manager must also have a background in psychology so he can handle all he workers effectively.
• He must also be able to apply safety and health standards all the time in the whole organization.

Introduction to Fluid Machineries and Hydraulics

The field of mechanical and industrial engineering is very wide. One of the sub-branches of this field is the study of Fluid Machineries. When you study fluid machineries, you will be encountering the following important terms, topics and concepts.

Pre-requisite subjects and concepts

Before you study fluid machineries, you should have taken up fluid mechanics first for you to understand the whole discussion. As mentioned above, fluid machineries deal with machines that use fluids as medium. So, you must know the basic properties of fluids:

• Density – the ratio of the fluid mass to the fluid volume
• Specific weight – the weight per unit volume of the fluid
• Specific gravity – a dimensionless ratio of the density of the fluid to the standard density. Typically, air or water is being used as standard density (reference)
• Viscosity – the resistance to shearing force or flow.
• Surface tension – the work necessary to transfer the molecules from the inside of the fluid (commonly liquid) to the surface to create one new unit area of the surface.
• Capillarity – rise and fall of a fluid. Capillarity is essential in small tubes but is negligible in larger diameter tubes.
• Bulk modulus of elasticity – the ratio of the change in pressure to the corresponding volume change per unit of the volume.

When it comes to computations in this subject, Bernoulli’s principle and equation is the common concept being used. This principle was derived from the law of conservation of energy, which states that in a system of steady flow along a streamline, the sum of all forms of mechanical energy will be the same at all points. Thus, making the sum of kinetic energy and potential energy remain constant.

Basic concepts of fluid machinery

Fluid machinery is the study of machines which use fluid as the major working substance. Note that when we talk about fluids, it could either be a gas (typically air or oxygen) or a liquid (typically water), as long as it has the ability to flow.  The main common purpose of fluid machines is to transfer the mechanical energy of the rotor into flow energy (kinetic energy).

Common types

Fluid machineries are often classified according to the working substance it uses. Basically, when the fluid used is gas, the machine is commonly referred as a fan (a blower or exhauster), or a compressor. On the other hand, if the fluid used is liquid, it is commonly termed as hydraulic machines or pump.

Gas-driven Machines

Mechanical engineering is a wide field of study. Fluid machinery is one of its most important subjects. Fluid machineries are machines in which fluid is their medium to transfer work. In studying fluid machineries, you must be aware that they are classified according to the types of fluids they used whether liquid such as water and oil, or gas such as air.
In the study of fluid machineries, when we talk about gas, it does not mean a gasoline or a fuel. Gas often pertains to air and other gaseous substance.

Fans and Compressors

Fans and compressors are two common types of fluid machineries that use air as their working medium. Do not get confuse with these two fluid machines. Take note that they work on different pressure difference.

Fans 

Fans are used to control the air movement in a low pressure, commonly at less than 10psi. Typically, a fan is sub-divided into two groups namely blowers and exhausters. A blower is a form of fan in which the air is being driven out to the surroundings through the discharge part of the system. On the other hand, an exhauster is a fan that works in opposite way the blower do. Exhauster is used to withdraw air from the surrounding through its suction part.

Fan performance

In studying fluid machineries, you should know the following concepts of fans:

• Fan static pressure head – the height of the fluid’s surface to the gauge point.
• Velocity head – head necessary to produce the flow of air.
• Total head – the sum of the static head and velocity head of the fan.
• Capacity of a fan – product of the fan area and velocity; the volume flow rate of the air.
• Air power or power output of a fan – power produced by the fan. 
• Brake power or power input to the fan – power being input to the fan usually from a motor.

Compressors

Compressor is also a fluid machine that used to increase air pressure (greater than atmospheric pressure) by decreasing its volume. Compressors, which are commonly powered by electric motor, are typically used in industrial applications that require air or other gases at high pressure. Compressors have two major classifications:

• Positive displacement compressors – these compressors have two types: the reciprocating, which are commonly used in internal combustion engines, and the rotary screw, which are often used in commercial applications. 
• Dynamic compressors – these can be classified as to centrifugal and axial flow compressors. 

Introduction to CNC Machines

The world of mechanical engineers revolves on machines and manufacturing processes. In daily activities of mechanical engineers, it is not quite easy to work on hands and tools alone regularly. The invention of Computer Numerical Control or CNC is a blessing to mankind especially to workers and technicians. Way back 1970’s, these machines are called Numerical Controls or NC, but later on changed into CNC when computers are widely available for use.

Industries where CNC is typically used

Today, CNC machines are widely used especially in fabrication industries where greater effort is necessary to produce finer steel and other metals. CNCs are now incorporated to machines such as lathe, milling, shapers and drilling machines. CNC machines are also used in metal-removing industries, electrical discharge industries, and wood working industries.

How a CNC works

CNC provides the operator a lesser task. However, a CNC operator should be able to know how to use this effectively to produce a quality work piece. Generally, a CNC is connected to a CAM or Computer Aided Manufacturing system and with a CAD or Computer Aided Design. These two systems will help the CNC improve whenever a change in the design or change in the process for the work piece is needed.

A CNC machine with computer control

Advantages of CNC machines

• CNC machines can be operated 24 hours a day. It only needs to be switched off for a minimal and occasional time. 
• One skilled and knowledgeable operator can operate more than one machine in a given time unlike having one operator for each machine. This would give a lesser cost for the company.
• Less effort and less skill is required for making any work piece with the CNC machines, unlike when working in a typical lathe machines and other manually operated equipments which requires a great training for the worker to perfect his operation.
• A single design of work piece can be made and multiplied with that same design with a very high accuracy.
• The software can help the designer make his design easily without the need of having a prototype. 

Disadvantages of CNC machines

• When a company decides to invest on CNC machines, they would lessen the numbers of their workers, thus will lead to unemployment.
• Most students that are taking up engineering or technical courses are not learning the manual operations of machines anymore. Most university is now teaching CNC operations only, thus pupils do not have the skill of operation lathe, milling, boring and other machines.

Bearings – Different Types Of Bearings

A bearing is considered as a machine component that restrains relative motion amid moving components to simply the wanted action. Generally, you can say a bearing is such device that’s utilized to enable linear or rotational movement, whilst decreasing friction as well as handling stress. Like wheels, bearings factually allow machines to roll, that decreases the friction amid the exterior of the bearing as well as the surface it is rolling over. It is significantly simpler to shift, both in a linear or rotary fashion, while friction is decreased – also this improves speed as well as efficiency.

How bearing works

To serve all the functions, bearing make utilization of a comparatively simple constitution a ball with external and internal even metal surfaces, to help in sloping. The ball carries the weight of the load itself – the power of the load’s heaviness is what forces the bearing’s rotation. But, not every load put force over a bearing in same manner. There’re 2 different types of loading such as: thrust and radial.

Different kinds of bearings

There’re several different types of bearings that’re intended to manage thrust load, radial load, or some grouping of the 2. Since different applications need bearings that’re designed to manage a precise type of load as well as different quantity of weight, the dissimilarities amid kinds of bearings concerns load kind and capability to manage weight!

Ball bearings

Such bearings are very common since they can manage both thrust and radical loads, however it only can manage a little quantity of weight. They’re found in a wide range of applications, for example in roller blades and also hard drives, however are likely to distorting if they’re overload.

Ball bearing

Roller bearing 

These types of bearings are intended to carry big amount of loads – the main wave is a cylinder that means the weight is dispersed over a bigger area, allowing the bearings to manage bigger quantity of weight. However, this structure means the bearing could handle mainly radial loads, however isn’t suitable to handle thrust load. For application where an issue is space, needle bearing could be utilized. Needle bearing works with minute thickness cylinders; hence they’re simpler to fin within smaller application.

Needle roller bearing

Roller thrust bearing

Such bearing are much like the ball thrust bearing, manage thrust load. However, the difference lies within the quantity of weight the bearing could manage: roller thrust bearing could support considerably larger quantities of thrust loads, and are thus found within car transmission, where they’re utilized to support helical machinery. Gear sustain in normal is a general application regarding roller thrust bearing.

Specialized bearing

Of course there are several types of bearings that’re manufactured regarding precise applications, like giant roller bearings and magnetic bearings. In fact, magnetic bearings can be found within high speed machines since it doesn’t have any moving elements – this stability allows it to sustain machines which move unconscionably quick. Giant roller bearing could be utilized to move very heavy and large loads, for example buildings as well as big structural components.

Large bearings for trains

Introduction to Welding – Modern Welding Methods

Welding is considered as sculptural or fabrication procedure what joins materials, normally thermoplastics or metals, by creating coalescence. This is often performed by liquefying the workpieces as well as incorporating a filler stuff to develop a puddle of molten substances which cools to turn out to be a powerful joint, sometimes with pressure utilized in combination with temperature of by itself for producing the weld. This is in disparity with brazing and soldering that comprise liquefying a lower melting point substance amid the workpieces to create a link among them, without liquefying the workpieces. Several different energy sources could be utilized for welding, comprising an electric arc, a gas frame, a laser, friction, ultrasound and an electron beam. Whilst most of the time an industrial procedure, welding might be done in several different atmospheres, comprising under water, open air, as well as within outer space.

Potentially welding is dangerous undertaking and safety measures are necessary to ignore electric shock, burns, vision damage, gasp of toxic fumes and gases as well as contact to intense ultraviolet emission. Till the conclusion of the nineteenth century, the lone welding procedure was forge welding, what blacksmith has utilized for centuries for joining steel and iron by heating as well as hammering. Oxyfuel welding and arc welding were amongst the 1st procedure to expand late towards the century, then electric resistance welding followed it. Technology in welding advanced very swiftly throughout the early twentieth century since World War I as well as II gaggle the requirement for inexpensive and reliable joining process. Following the war, different contemporary welding technologies were come into action.

Let’s have a look at the different types of modern welding methods available:

Shielded Metal Arc Welding

Known as stick welding that utilize a bar or in technical term it’s called an electrode which has a residue coating over it that melts or burns to develop a screen from oxygen, and few bars have packing metals incorporated to the wrapping to accelerate the welding procedure. Shielded metal arc welding is considered as the ideal procedure to weld outdoors.

Metal Insert Gas Welding (MIG)

MIG welding is a procedure which utilizes a wire pool for feeding wire to the joint as well as has a container of gas which gushes from the appliance to the welding grip to shelter the weld form air about it. The greatest portrayal in an assessment perspective is a cycle’s brake wire that has a cable running through which feeds incessantly to the joint, however; also this cable has a gas streaming via it that protects the weld from the air.

Tungsten Inert Gas Welding 

Also known as TIG welding is a torch which has a gas streaming through with a non delicate bar created from tungsten which warmth the metal as well as the packing metal is detained in other hand and physically incorporated when required. The non-consumable bar is only a bar that makes the arc to warmth the metal. It doesn’t put in to the welding packing material itself.