DOL Starter controling Diagram

Direct On Line Motor Starter includes tracking MCCB, Contactor and overload relay for protection. An electromagnetic contactor that can be turned on is a thermal overload relay under error conditions.The contactor controls with the start and stop buttons, and the contact assistant on the contactor is used, across the first button, as a holder for contact. i.e. the power connector is turned off while the engine is running. Usually up to 5HP induction motor we choose the first DOL method.

Direct On Line Starter (DOL) Terms of Service:

To start, the contactor is closed, using a full line voltage on the motor stator windings. The motor will pull the highest inrush current for a very short time, the magnetic field of the metal, and the current will be limited to the Locked Rotor Current of the motor. The motor will improve the Locked Rotor Torque and start accelerating towards full speed.

As the engine speeds up, the current will start to decrease, but it will not slow down until the engine is at full speed, usually 85% of the corresponding speed. The first real current curve is the car design function, as well as the terminal voltage, and is completely independent of the car load.

The load on the motor will affect the time taken for the engine to accelerate at full speed and therefore the maximum duration of the initial current, but not the maximum initial current.

As long as the torque generated by the engine exceeds the torque of the load at all speeds during the first cycle, the engine will reach full speed.

Advantages of DOL Starter: -

1. These are the simplest types to begin with.

2. The most economical and cheapest launcher.

3. Maintenance costs are very low.

Disadvantages of DOL Starter: -

1. It pulls the highest inrush current at the start which is 6-8 times the engine limit which limits its use to motors of only 7.5 KW.

2. It will apply high thermal stress to cars which will reduce the life of the vehicles.

3. The current High Starting will lead to a voltage drop.

Ferrite Bead

Our laptops are our daily resource, we can use them for over 6-7 hours but have you seen the little things waiting for us at the end of it.

They always looked like useless additions that never made sense to anyone but these little cylinders called Ferrite beads. These small letters are a reason to reduce distraction.

Any device that works with power transmission also selects power from other devices. So are our laptops with power switches on the switch that enable them to transmit radio waves. This process is called EMI (electromagnetic interference). This EMI leads to unavoidable power loss with the help of this tiny cylinder. Loss of power will obviously result in less charging of your laptops to reduce that and radio frequency noise can also be reduced.

Air Conditioners with Inverter technology

The latest and most effective technology available on the market today is Inverter Technology for air conditioners. Inverter technology is designed in such a way that it can save 30-50% of the electricity (units used) over normal air conditioning.

How does the air conditioner work?

The air conditioner during the cooling process, takes indoor air, cools it by passing it to the evaporator and then throws it back into our operating room with indoor air. Along with the evaporator air conditioner it also has a compressor that presses gas (refrigerator) to AC to cool itself and cool the incoming indoor air from the chamber.

In standard air conditioner:

The compressor is off or on. When turned on, it works at full capacity and consumes the full power it is designed to use. When the thermostat reaches a temperature set at AC, the compressor stops and the fan (to AC) continues to operate. When the thermostat senses that the temperature is rising, the compressor starts again.

On Air Conditioner with Inverter technology:

Inverter technology acts as an accelerator in the car. When a compressor needs more power, it gives you more power. When it needs less energy, it gives less energy. With this technology, the compressor remains open, but draws less energy or more power depending on the temperature of the incoming air and the level set by the thermostat. The speed and power of the compressor are adjusted accordingly. This technology was developed in Japan and used there successfully in air conditioners and refrigerators. This technology is currently only available on separate air conditioners.

What are the benefits of Inverter Technology?

All air conditioners are designed for high loading. So 1.5ton AC is designed for a specific room size and 1 ton for a different size. But not all rooms are the same size. A standard 1.5ton air conditioner will always operate at high power requirements when the compressor is operating. An air conditioner with inverter technology will work continuously but will only absorb most of the energy needed to maintain the desired temperature. It therefore automatically adjusts its volume according to the requirements of the cooling room. So draw very little power and use smaller power units.

Although airconditioner with Inverter Technology adjusts its volume based on the needs of the room, it is very important to install the right amount of air in the room. Please make sure you check the room and air conditioner capacity before purchase. Keep an eye out for this space as we are in the process of making a comparison of energy saving on different air conditioners.

Are Inverter technology air conditioners slow to cool?

In comparison, inverter tech AC changes the flow rate of the refrigerator based on room temperature. When the temperature is low, the flow rate is low, when the temperature is high, the flow rate is high. And it does not always turn off the compressor. It simply ensures that when the temperature setting is 25, it is maintained at that level.

So the difference is: the non-inverter AC will cool down, while the inverter AC will cool down much better. And thus one may feel that the AC inverter is neither cool nor fast.

The lesser-known benefits of Inverter Technology

Ordinary engines require 3-4 times more current (over current performance) in the beginning. Therefore the size of the inverter / generator required to use any AC or Refrigerator is greatly increased. But Inverter Technology air conditioners and refrigerators with flexible speed engines that start slowly require very little performance at first. Therefore the size of the inverter / generator needed to start is small. For example. A fixed speed of 1.5 ton AC operating at about 10 Amp current may require up to 30 Amp current when starting as well as a 5 kVA inverter / generator. But the inverter technology Air Conditioner requires about 6-7 Amp current and not too much at first and thus a 1.5 kVA or 2 kVA inverter / generator is good enough to support it.

Normal motors have a very low power factor. In commercial and industrial connectivity there is a low power factor charge and a high power factor discount. The inverter technology engine will have a power factor close to the unit (or 1) which not only results in less power consumption but also helps to get discounts on a better power factor.

If you plan to use Solar PV air conditioner, it is best to use inverter technology air conditioner or refrigerator as it not only reduces the size of the PV panel because it consumes less electricity, and reduces the size of the inverter to integrate the PV panel .

How you can use the 3 phase change over switch in home

Basically, there could be two type of phase changing device, one could be an automated one with a digital numeric relay for automatic change over and the another one is a basic manual one which have to be operated by a human. 

For typical domestic use, the device illustrated bellow have two more identical units mounted over a board with some indications regarding the number of phase available and the currently applied change over status.

The red, yellow and blue indicating lights will be in two sets in which the first set will be pointing towards the availability and healthiness of all the respective three phases at the incoming side of the device. By looking at these indication, one can determine that out three phases, which phase is available. 
Similarly the second set of indication lamp is showing the status of the three phases at the outgoing end of the device (Which will be the actual status of the three phases being fed to your home).

whenever there will be an phase outage due to faults or blown fuses at the power distribution feeder end, both sets of same coloured indication lamps will stop glowing to which phase they are assigned for (e.g. if only both sets of Yellow and Blue indication lamps are working that implicates that power supply to Red phase have been disrupted).

And now comes the part where the actual operation of the phase converter/selector will be done. There would be three similar rotary switches with three/four similar markings on it, so lets pick one switch for ease of understanding. Normally, the following would be the positions of the selector switch, for R Phase selection, the knob on switch will be indicating 1 or R. For Y-Phase, the knob will be positioned on 2 or Y and similar for the 3rd of Y phase.  

Suppose the Red indication lamps are not working, but other two are working, then the switched have to be adjusted so that only Y and B phase will be supplied further, hence the R-Phase's knob will be rotated and can be placed on either position number 2 or 3 from its earlier position of 1 so that the power line of R phase is connected to that of Y or B-Phase.

So, when the above mechanism is applied, all the 3 indication lamp on the second set will start working although the one indication lamp on the incomer side is still dark, this shows that the changeover have been completed successfully.

Things to remember !!

• Never ever do this change-over operation with your main supply on, in order to avoid a possible flashover, always drop the main MCB of your home before operating the device.
• Never ever use this change over device if you have a direct 3-phase device like flour-mill or water pump of high capacity as the two similar phase will damage the device.
• Always remember to re-position the knobs to its original position once the phase have been restored if the damage caused by heavy flow of current over a single phase have to be avoided.

Working of tester

A Neon screwdriver or tester is commonly used to check the live wires. If the circuit is live, the neon bulb glows. We can also name it as voltage testing device. However the terms Phase checker, Line tester, Live checker and Positive presence checker is also used to identify the instrument. Here is the full construction with all parts indicated.

Metal Rod:

It is a metallic rod. The lower tip of the rod is specially chamfered to a specific screw design. This end is connected with the live wire. The upper end of this rod is completely cylindrical and it joins with the resistor.

Resistor

Resistor reduces the amount of current in the circuit. This current reduction provides a safe limit for the neon bulb. Next to resistor, the neon bulb is connected.

Neon Bulb

The neon bulb is used as the current indicator. When connected to live circuit, this neon bulb glow and we can know that circuit is live. If there is no current the bulb will not glow.

Spring Elements

Next to neon bulb a metallic conductive spring element is connected. It serves as a bridge or junction between the bulb and cap.

Cap

Next to spring a cap connects. This cap serves two purposes. Its internal sides keep all the equipment tightly pressed within the plastic assembly. Whereas its external side in pressed by the finger. (Full working explained in the working section)

Clip

A clip is conventionally connected with the cap.

Plastic Assembly

The plastic assembly surrounds the whole arrangement and its purpose is to insulate the entire design from human body so as to prevent shock and hazardous conditions.

Working

During working the low end of the metallic rod is connected with the live wire whereas the upper end of the cap is pressed by the human finger. The internal resistance of tester connects in series with the human body. Remember that this internal resistance is very high typically it is the order 200 k. Now the circuit completes and limited current runs through the human body. This current also flows through the neon bulb and it lights up if the circuit is live.

There are a few precautions that should be employed while using the tester. However, two most important precautions are mentioned here:

• The tester should only be used when you are sure that voltage is within 500 V. Also make sure that proper resistor is connected. Never connect the instrument until you are 100% sure.
• Always use the good quality instrument, you can save a few bucks on low-quality material but it can harm your life.

Why don't birds get electrocuted sitting on power lines?

Current flows in a loop[ which means the circuit is closed]. A bird sitting on a transmission line does not complete the circuit. If the same bird keeps one leg on one line and another leg (or any part of its body) on another line(or the neutral points), then it will get roasted.

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Consider this circuit where a bird sits on the wire:

The values R1 and R2 are resistances of the line. Electricity takes the path of least resistance. The two legs of the bird which is perched on the same line does not complete the circuit. The R_Bird( resistance of the bird’s body) is much higher than that of the line, so the bird might not experience high current. The potential difference between the two legs of the bird is same( since the resistance of the line is the same throughout).The current flows on.The bird is safe.

Now consider this scenario:

A bird sitting on a line decides to fly away and raises the wings. With one wing touching the neighboring line and the leg on the first line, this creates a closed circuit. Thus electricity (following the path of least resistance) will detect a potential difference between the wing (which touches the other line) and the leg(which is placed on the first line). The current tries to take on that path creating a short-circuit. Eventually the bird gets zapped and falls off the line. Now the current will continue to flow on.

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The lesson we learn here is that when ever we play with electricity, make sure you (your body) does not close the circuit. When we poke our fingers into an electrical socket we get shocked because our body will offer a lower resistance . Thus a potential difference will be created between your finger and the feet( which is placed on the floor acting as a neutral point).

Is it bad to charge your phone over night?

As we know, our smartphone batteries are bad as they barely last a day. At the earlier days when we buy it, it’s the fault of smartphone manufacturers. But what about several days later? It’s to some extent your own fault for charging it wrong this whole time. For example, charging phone overnight.

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Firstly, let’s have a look at the following saying: charging phone overnight, or more specifically, charging phone when it’s already fully charged, will keep it in a high-stress, high-tension state, which will surely do wear down the battery with lasting damage at the same time.
So, is it true? Is charging phone overnight bad?
Well, you’d better ignore that. We couldn’t be more wrong.
And the truth is that Charging phone overnight will not harm your battery in the slightest. Any device with a Lithium Polymer battery must incorporate a charging circuit that will cut off charging power when the battery reaches 100%.
Besides, the smartphone battery is as smart as the phone itself. Apple, Samsung and all the top tech companies, almost of whose products use lithium-based batteries.

That aside, however, Lithium-ion batteries don’t need to be charged all the way to 100%. While your phone runs troughtout the night, it loses battery life. And this will cause the charging mechanism to kick in over and over again as amounts of battery drain occurs during standby when checking emails, receiving text messages, and updating various apps while you sleep.

Let’s take an example. If you head to bed at 11 p.m. with a battery percentage in the single digits, your phone will be fully charged by 2 a.m. If you wake up at 6 a.m., that’s 4 hours that your phone stays plugged in with a full battery.

So what is the optimal way to charge your phone? That is to keep them charged between 50 and 80 percent.

Additionally, we have to mention Charge Cycles, that is, your battery goes from empty or near-empty to full. Every phone battery has a limited number of charge cycles before the end of its life. An iPhone has about 500 charging cycles. When charged up from 90%, only 10% of a complete charge cycle used. Whereas, when charged up from zero, then a complete charge cycle done. Or you’ll actually shorten your battery life if you do so.

Surely, here is another good idea for charging, or portable charging. And that is to take a power bank in hand, in pocket.