SCROLL COMPRESSOR ! By Imran

A scroll compressor is a specially designed compressor that works in a circular motion, as opposed to up-and-down piston action.

Scroll compressors are becoming more popular for use in HVAC systems, as they are more reliable and efficient than reciprocating types. A scroll compressor has one fixed scroll which remains stationary and another moving or orbiting scroll that rotates through the use of a swing link. When this happens, the pockets of refrigerant between the two scrolls are slowly pushed to the center of the two scrolls, causing the reduction of the volume of the gas. It is then discharged though the center port to the condenser. The advantage of a scroll compressor is that it has fewer moving parts and less torque variation compared to the reciprocating compressor. This advantage is translated to a smooth and quiet operation. The scroll compressor is also known as scroll pump or scroll vacuum pump. Scroll compressors can be applied in several different ways to meet a homeowner’s needs for efficiency, comfort, and affordability. Single-stage compressors are found in most home cooling and heating systems. The simplest and least expensive type, they operate at only one speed. Single-stage units can cool or heat a home efficiently. Two-stage compressors operate at two different speeds, more closely matching their cooling or heating output to the exact needs of the home. The ability to run at a lower, more efficient speed helps remove excess humidity from the air while saving energy and the compressor can switch to its full capacity if needed to hold temperatures steady. Two-stage systems are typically more energy-efficient than single-stage systems. Variable-capacity compressors provide exceptional control of home temperatures and humidity, because instead of operating at one or two settings, they can modulate their capacity in very small increments throughout a wide operating range. This allows for very precise control of cooling and heating, keeping temperatures even throughout the home and saving energy in the process. While variable-capacity systems tend to be more expensive, they provide exceptional savings on monthly energy bills and can be up to twice as efficient as single-stage models.

Difference Between Star and Delta Connection ! By Imran

Difference Between Star and Delta Connection are as

The terminals of the three branches are connected to a common point. The network formed is known as Star Connection. The three branches of the network are connected in such a way that it forms a closed loop known as Delta Connection. In a star connection, the starting and the finishing point ends of the three coils are connected together to a common point known as the neutral point. But in Delta connection, there is no neutral point. The end of each coil is connected to the starting point of the other coil that means the opposite terminals of the coils are connected together. In Star connection, the line current is equal to the Phase current, whereas in Delta Connection the line current is equal to root three times of the Phase Current. In Star connection, line voltage is equal to root three times of the Phase Voltage, whereas in Delta Connection line voltage is equal to the Phase voltage. The Speed of the star connected motors is slow as they receive 1/√3 of the voltage but the Speed of the delta connected motors is high because each phase gets the total of the line voltage. In Star Connection, Phase voltage is low as 1/√3 times of the line voltage, whereas in Delta Connection Phase voltage is equal to the line voltage. Star Connections are mainly required for the Power Transmission Network for longer distances, whereas in Delta connection mainly in Distribution networks and is used for shorter distances. In Star Connection, each winding receives 230 volts and in Delta Connection, each winding receives 415 volts. Both 3 phase 4 wire and 3 phase 3 wire system can be derived in the star connection, whereas in Delta Connection only 3 phase 4 wire system can be derived. The amount of Insulation required in Star Connection is low and in Delta Connection high insulation level is required.

PCB fault recognise ! By Imran

Chemical fluid leakage How To Recognise Five of the Most Common PCB FailuresThe presence of any chemical fluid that has leaked from a component can seriously damage the PCB and cause failure. Most chemicals are removed in the manufacturing process, but often trace elements are left behind. Inside the packaging of a component, leaks can happen, which cause rapid aging of the semiconductor or package. This chemical leakage can eventually cause shorts or become corrosive.

Issues with the soldering process Solders are the part that provides the necessary means of contact between the component and the circuit, without it the PCB would not work. There are a few solder issues that can cause failure, but the most common are flux contamination and poor processing conditions. Some flux residues can absorb moisture which can become conductive, causing short circuits. If the solder process is not properly set up and controlled, it can lead to open joints and contaminated solder Component barrier breakage The barrier of a component is there to protect the component from the outside environment and also to give a way for the component to connect to the circuit. If this barrier is broken, then the component will become exposed to environmental factors such as oxygen and humidity, which can cause the component to age and then fail. Physical problems with materials The materials used in a PCB can often encounter problems that will cause the board to fail. During the manufacturing stages, if a layer of the PCB is misaligned it will cause short circuits, open circuits and crossed signal lines. If there are psychical defects with the materials such as fractures, voids and delaminations they will seriously affect the performance of the PCB. Failure can also happen if the materials used are impure

Symptoms of Heat stress ! By Imran

The most common signs and symptoms of heat exhaustion include: Confusion Dark-colored urine (a sign of dehydration) Dizziness Fainting Fatigue Headache Muscle or abdominal cramps Nausea, vomiting, or diarrhea Pale skin Profuse sweating Rapid heartbeat Treatment for Heat Exhaustion If you, or anyone else, has symptoms of heat exhaustion, it's essential to immediately get out of the heat and rest, preferably in an air-conditioned room. If you can't get inside, try to find the nearest cool and shady place. Mohammad Imran (HVAC Engineer)