PAANO GUMAWA NG DIAGRAM NG WYE - DELTA STARTER

Ang Wye - Delta starter ang pinakamadalas na ginagamit na reduced voltage starter.

Base sa pangalan, may dalawang connections sa nabubuo: Star or Wye, at Delta. 

Before we start, let me take note of the following cases that occurs in circuits

1) Once a Coil is Energized, there will be  transition of Contacts position. Ang Normally Closed Contacts ay nagiging Open. Ang mga Open Contacts naman ay nagiging Close.

2) Ang Pushbutton bilang isang trigger switch ay may karaniwang koneksyon: Ang Coil ay madalas naka-Series, samantalang ang Contacts ay Naka-Parallel.

A) Initial Control Circuit

•  Circuit 1: Contactor M1 Connection

  

Gawa ng diagram na pang.direct on line muna.  Start and Stop Pushbutton, kakabit ng Contactor M1, at Green Pilot light.  

Naka-series ang Stop pushbutton, Start pushbutton at Contactor Coil M1.  Sa diagram, once na-press ang Start PB switch, ma-eenergize ang M1 coil at magcloclose ang Open Contacts M1.

• Circuit 2:  Green Pilot light Connection

After then ng Start PB, ay naka-series sa Contactor Coil ang Green Pilot light which means bukas kaagad ng RUN STATUS na ilaw pagkapress nito.

• Circuit 3: Overload Relay Circuit

Gawa ng Overload Relay (OL) contacts  na Normally Open at ikabit nang naka-series sa Orange na Pilot light o TRIP STATUS Indicator. 

Ibig sabihin, pag natrigger ang overload relay coil sa power supply, magcloclose ang OL contacts na N-O, makokompleto ang circuit at iilaw ang Orange light. 

B) Timer Connection

• Circuit 4: Timer Coil Connection

After ng Start Pushbutton ulit, naka-parallel sa Green pilot at at M1 coil, gawa ng koneksyon para sa Timer Coil.

Once na na-press ang Start PB, naenergize din ang Timer Coil. Mag-umpisang gumana ang timer.

C) Timer Contacts Operation - Related (Star and Delta Connection)

After ng M1 Contacts, gawa ng naka-parallel kay M1 Coil, na Timer Contacts, N-O at N-C.

• Circuit 5: Star connection

After M1 contact, ikabit Ang TR contact na Normally Closed, naka-Series din sa S1 contact na Normally Closed (N-C), at M2 coil. 

Sa sandaling ito, closed na ang Circuit ng M2 at S, na makakabuo ng Star or Wye Connection.

• Circuit 6: Delta connection

Nakainterlock sa Normally Closed (N-C) TR contacts and Normally Open (N-O) TR contacts.

Gumawa ng series connection sa N-O TR contact ang S1 coil.  

After gumana ng timer, at natapos ang nakaset ng cutoff time, naenergize ang coil ng S1. Ang N-C TR naman ay nagiging Open. Kakalas ang S1 contacts at tanging ang M1, M2 lang ang mga closed contacts na kokompleto sa ating Delta Winding.

30 DIY HOME REPAIRS HACKS THAT YOU CAN DO DURING COVID 19 QUARANTINE

1) Leaky Washing Machine (case no. 1)

Solution: Check the hose at the back of the washing machine where the water supply is completely ng from. The hose comes with a rubber and even when a small crack in the rubber creates big damage for the entire hose connection.

Turn off the washing machine. Turn off the water supply. Replace the hose if you have spare (Rubber seal does not come separately but in a set with the hose).

2) Door Handle that is Loose

Solution: You may check all the side of the door handle. Best is to unscrew all spare parts as much as possible then reinstall them. Most common issue for door handles is just loose screws.

3) Fixing a Clogged Kitchen Sink Drain

Solution:  (a) It is usually caused when you don't use kitchen sink filter. You may apply chemicals like Mr. Muscle, or Dac Drain Opener.

(b) If you don't have chemical, you may remove P-trap under the sink carefully. In this spare part, all solid foods are usually just trapped in this area.

(c) You may also use Snake pipe. Remove the drain cover first. Then insert the pipe. Make circular rigid motion. Then pull the pipe.

Hacks: You may declog the oil that has hardened by two basic household items - Bank ng soda + Vinegar.  These 2 makes a good acid that melts some solid stuffs and declogs drainages.

4) Fixing Clogged Washbasins in Comfort Rooms

Hacks: Use any of the following
    (a) Long single core / stranded wire that can penetrate into the drainage pipe.
   (b) Straightened hanger
   (c) Big cable tie
   (d) Tie wire
 
5) Patching a Hole in the Dry Wall

Solution: You may use All Purpose Filler mixed with Water then allow to dry. (Gypsum Powder is only reliable on gymsum board. Never use gypsum powder for cement since it would only be for temporary fix. Best recommendation if we use stronger and Branded type All Purpose Fillers instead. Believe me, this is based on experience.)

Note:  As per other articles in the internet, common items such as Crayons of the same color with the wall, Candles, or even Bar Soap can be used. However, this type of materials only patch holes for a temporary period of time and easily melts with heat or water.

6) Removing Wall Marks

Solution: Sponge and Soap will Do. But if you have a white cement wall, and you have a spare Sandpaper, having an extra rub with the sanding paper will make thing easier. Just be prepared to clean the cement residue afterwards.

Hacks: Jif (Cleaning chemical for oil stains) dubbed on sponge with Water can also be used to clean. However, make sure you use as little as possible as Jif can also damaged paint.

7) Fixing Squeaky Sound for Door

Solution:  WD - 40 which is normally used for lubrications of spare parts for bicycles and motorcyles, can also be used here. Apply this to the hinges as per needed.

Hacks: You may apply also common kitchen material such as Cooking oil.

8) Sharpening Dull Scissor at home

Solution:. Use File to sharpen it. In case you have Sandpaper, you may also rub a portion of it to the edges of the scissors.

Hacks: Aluminum Foil will also be helpful. Check aluminum foil from cigarettes or the foil used to insulate foods in the kitchen. Stacks sheets of these foils, or fold them in half to thicken them. Then cut with the scissors for at least 8 times. The blade will be sharper afterwards.

9) Door Bumping on the Wall

Solution: You may make a DIY door stopper with a spare wooden piece (2 x 2). If you have a Hacksaw, cut the wood into Triangular piece to make a door stopper.

10) Dents on the Carpet

Solution: If you have a Scraper and Adhesive, you may remove the carpet, then reapply it properly. Make sure all areas of the carpet stick to the floor.

Hacks: Place Ice Cubes on the dent of the carpet and let it melt there. You may also use Blower to dry up the carpet faster.

11) Locked up Door

Solution: Place a Hard / Thick card ( old Credit Card, ID Card, or Discount card) in between the door frame and the door to gently push the lock and open it.

12) Fixing Broken Hose / Leaking Water for Outdoor Gardens

Solution: While you have to save the hose by using Super glue, take note that water pressure damages slowly and even very small hole causes great damage after a while. Best is to cut the broken area and reinstall the hose without any damaged part.

13) Vacuum Cleaner Hose that Keeps Getting Out

Solution: Use Duct tape to fix the hose into the vacuum. Duct tape is best applicable to plastic items (You may also use it for Trash bins, paint trays and even mosquito nets)

Hacks: Masking tape is also helpful.

14) Flyscreen of Kitchen Net Broken

Solution: Replace kitchen net. You may ask assistance with other family member as this usually done in pairs by technicians.  However, if you are confident that you can pull this DIY home repair properly, there is no harm in trying.

First measure the net to be used. Gently cut with Big Scissor. Remove the door. Then replace the kitchen net. Make sure it is properly spread out. For this procedure, there are DIY videos in the internet that you can follow easily.

Hacks: If the damage is small, you may use Nail Polish (colorless) to ensure the broken parts stay in place.

Plastic Sheet or Acetate can also be used to cover the hole for the Flyscreen. You may use Transparent Scotch Tape for tape it.

 15) Fixing Furniture with Screwdrivers

Solution: Loose joints, hinges, spare parts that are connected by screws can be tightened during your spare time. Use the correct screw driver.

You may also use Drill machine, usually with drill bit of 3mm size, not only for drilling holes for the screw but to tighten or untighten screws as well.

16) Screw Hard to Remove

Solution: In case you don't have drill machine, you may use Screwdriver and Wrench to be able to twist the screwdriver more easily.

Hacks: You may use Rubber Band or any type of thin Rubber. Simply put it on top of the screw before applying the screwdriver. In this way, friction will add resistance to the screw, causing the screwdriver to take a more grip onto it.

17) Adjustable Wrench Missing

Hacks: If you have a Bolt and Knot, simply put the Bolt horizontally across the other bolt that needs to be untightened and removed, with the head on one side. Then use Knot, to  lock it up on the other side of the bolt. To turn it around, you may use Multifunction Pliers. Resourcefulness is most convenient for this case.

18) Water Leakage from AC Drain (Split type)

Solution: Water leakage means clogged drainage. Use Vacuum Machine to pull out some debris from the Clogged pipeline
First turn off AC, then find AC Drain line. Most AC Drain are outside, near condenser unit. Point the vacuum hose to the drain line to suck out any solid item clogging the unit.

Hacks: (a) Use one cup of Bleach for every one cup of Water Ratio (1:1). Pour on top of the drain pipe and wait for 30 minutes.

b) You may also use Tie Wire that can act as Snake Pipe. Two persons can best fix the issue with this method.  One person will insert the Tie Wire from the Top of the drain pipe near the indoor AC unit. Another person on the end of the Pipe. Once inserted, the second person will pull the Tie Wire strongly. Some debris will surely also be pulled out with this method.

c) For minor clogging, and if you don't have above materials, you may use Blower. Kindly point the blower from the top of the drain pipe, near Indoor Unit. This method is pushing the solid items into going out of the drain pipe, opposite process of Sucking out when you use Vacuum cleaner from outside.

19) Quick Fix for Damaged Wall Paints

Solution: Check out the following steps

  (a) With Masking Tape, cover all outlets, switches and other devices. Also cover the floor either with Plastic Roll or Cartoon for protection from paint drops.
   (b) Remove dilapidated wall paints with Scraper and Paint Thinner.
   (c) Prepare the wall. Smoothen the wall with Sandpaper. For fixing the holes, you may use All Purpose Filler.
   (d) Application of Primer Paint. Then leave the wall to dry.
   (e) With medium size Paint  Roller, apply first coating of the Paint. Then let it dry for 3-4 hours. You may use Small Brush to cover or paint edges and corners.
   (f) Apply second coating of Paint. Then let it dry.

Hacks: For big holes, you may use Gypsum tape available upto 8 inches.

20) Removing Sticker from Appliances

Solution: You may remove unnecessary stickers during your spare time with Paint Scraper. Dab with water first, then gently use scraper.

Hacks: Gently apply Cooking Oil with small soft cloth.  Dun the oil and let it be absorbed for a few minutes. Then gently rub out the sticker.

21) Fixing a Leaking Shutoff / Angle Valve

Solution: If minor problem, you may apply Teflon Tape counterclockwise and wrap around the leaking area carefully.

If there is a major water leak and needs replacement but you don't have spare shutoff valve, temporarily turn off the Angle Valve for the affected pipeline.

Hacks: If in case you don't have even Teflon Tape, you may contain or lessen the leakage by wrapping the area with leak with a flat Wide Rubber.
 


WD-40 QUICK FIXES (Unlike the previous cases that mention first the maintenance issue and the home repairs needed afterwards, below descriptions are just applications of WD - 40 that you may use at home.

22) Removing paint stains on carpets
23) Removing paint stains in bath tubs
24) Cleaning oil spots in Garage by applying WD-40, then use pressurized water with Hose
25) Removing stains from Toilet Bowl. Apply WD-40 then use toilet brush.
26) Removing hair dye stains on furnitures or even clothes
27) Squeaky sounds of drawers, door closers, etc.
28) Removing crayon markers from walls (in case you have kids)
29) Refurbishing plastic furnitures. Renewing faded colors for old plastic chairs or tables.
30) Lubricating sliding door wheels / rollers, windows, floor mechanisms, door locks, etc.

Home Maintenance While on Quarantine Due to Covid19

Now that you are at home 24/7, you have time to notice the things that need repair in your house.

Did you observe your door to be squeaky? Is your washbasin in the comfort room or the kitchen sink drainage clogged? Are there any lights that are blinking or about to be busted? Is your AC working as good as before? Are there any water leakages during rain? Now that everyone is advised to stay at home, it would also be best to be the good handyman of your own house. No choice huh?

Here are some tips to prepare you for such works:

1) Check all your old stuffs and tools and put them all in one toolbox (if you don't have box you can at least put in a drawer or bag).

For instance, you may have bought screwdrivers before and just put it in one cabinet while the other tools are in the store room. In this way, it would be easy to find them in case of home emergencies or home repairs you will do.


2) Learn the basics of home maintenance and how to do them properly.

Since, today is an age of information, you may read e-books, tips on the internet, videos for D-I-Y home repairs that may come through you tube or blogs like this. Basic understanding of electrical, plumbing, carpentry works and even AC system (in case you have) is very useful.


3) Practice a well organized problem solving.

Like what we have learned during our elementary days, we will use the 4W's and 1H - What, where, when, why and how.

3.a) WHAT is the maintenance issue?
WHAT are the tools that you can use?

For example, you may have problems with too much oil on the wall due to cooking. However, as you searched with your old stuff, you have an Aluminum Sheet Cutter. Lucky for you to find also spare aluminum sheet and some nails and hammer you can use to apply the aluminum sheet on the the wall so it would be easier to remove oil stains. Or you may also look for adhesive so you will only stick through the wood or concrete the aluminum sheet. With the right materials, home repair is so much easy to do.


3.b) WHERE do you exactly need to fix?

For example, there was a main circuit breaker trip. You may have to check all appliances and if you have plugged in a faulty machine, or check if there are any burned outlets.  Once you are able to locate, you can isolate the circuit by turning off the branch circuit breaker, and reset the Main circuit breaker.

3.c) WHEN does the issue usually occur? Or WHEN did the problem start?

This can best be understood by knowing the history of the issue. For example, you suddenly noticed your wooden entrance door is disaligned and almost all hinges are loose already. As you observed further, there are some bearing of the hinges that are missing.  Your kids may have played with the door hinges. You may ask them when did they notice the hinges to be loose / broken?  This may have been  alsoonly may only one missing bearing on the hinge first then got worse after few weeks.  Then you may encourage everyone at home to be more aware of these kind of things.

 WHEN is best time for repair? Since you are in home quarantine and all are in the house, you should also take note of your schedules. Use the time on days that the other family members are in different location so no one will be messing up your work.

3.d) WHY did the problem occur? You have to know what caused the problem to understand and learn how you can fix it. The most convenient way is the FISH BONE DIAGRAM METHOD. (I will discuss this on a separate article)

3.e) HOW can you solve the problem?

You have to know how to isolate the issues that are minor and major. For the minor works, you may fix all of them by yourself, or with the aid of your friends that you can call through phone. However, for major works, you may learn how to CONTAIN the problem.

Note: Containment is the process of preventing more damage to a property, machine or anything that has also fault or problems.

Containment means stopping water leakage, making remedies for very noisy drops of water, resetting electrical breaker when there is power trip, turning off of angle valve for broken water pipes and stopping water supply for affected areas.

How to Check if AC Compressor Needs Replacement

Paano nga ba icheck ang compressor Kung kailangan bang palitan o Hindi.

Short to Ground (Pinakabasic at usual na  na test)

Ang compressor ay may tatlong winding terminals (T1, T2, at T3). 

1) First, disconnect power supply for the compressor

2) Now, with multimeter, set to Ohms reading.  One test probe to the body / housing and the other one to any of the winding terminals. Dapat lalabas ay 0 ohms. Pag may reading 0.0 ohms, ibig sabihin, damaged na ang winding at may part na nadidikit sa housing ng compressor 

Example:

1) Ground to T1 : 1.39 ohms

2) Ground to T2: 2.45 ohms

3) Ground to T3: 3.23 ohms

Sa tatlong results, lahat lumabas n grounded na, Kasi may nababasang Ohms kahit walang power supply.

2)  Continuity Test - Iset Ang multimeter sa continuity setting.  Icheck ang continuity sa mga winding terminals. Kung lahat ng testing ay 0.0, ibig sabihin sira ang compressor. 

T1-T2: 0

T2-T3: 0

T3-T1: 0

Pag ganito Ang results, siguradong sira Ang compressor. 

Remembering and Understanding Kinematics

Good day.
Kinematics, when I was a child, was a little too technical for me, and a little boring.
Back then, I would remember just busy jotting down notes but never really understanding them and absorbing the concepts behind them.

But hey, now that I am working, I finally found it interesting. It is something that is very fundamental in our technology nowadays.

Transportations were made easy: ships, trucks, cars, gondola, etc.When we are riding on airplane, have we tried to think about how the inventors were able to check the speed, time, velocity and acceleration as to how the plane should go? When we are on a moving car, have we asked as to how scientist and inventors could predict how fast the car can move with respect to time, in certain velocity and acceleration. Even the baseball's movement we can trace using Kinematics, and the much more complex Rocket launches in space.  Falling from high points such as buildings and cliffs, we have also been able to calculate using Kinematics.  In this way, we were able to use them and discover bungee jumping, going down from planes on parachute, calculating falling objects from the top of buildings, etc.

KINEMATICS 

In particular, kinematics is a concept in physics involving motions. In fact, it is from the Greek word "kenesis" which means "moving".   Terms involved in Kinematics :  Scalar, vector, displacement, speed, acceleration, velocity.

 Basic equations in kinematics:

1) vf = vi + at                                               not included :   x  

2)  x = vi  t   +   (1/2)at^2                             

3) vf^2 -  vi^2 =  2as                                    not included :   t

4)  x  =   (  vf + vi) / 2   *   t                         not included :   a

also definitions  such as

      speed =   a  * t

      speed =   s  /  t      (displacement over time)

      acceleration,   a  =   v  /  t

here vi = initial velocity

 vf = final velocity

t = time

a = acceleration

s = displacement

Back then in college, I would remember, having to check other key points and techniques to remember the formulas such as these:

•  difference of squares of v  is  (2as)
•  vf = VIAT   because of   (vi + at)
•  x  = (average of v's) * t       since v (ave) =  ( vi + vf)/2
•  x  = integral of v, is s.     Integration of formula for v, with respect to t,  from  vi t  + at       becomes     vi  t  +    1/2  at^2

Below are list of sample problems I have:

1)  How long will it take for a car starting at rest and a = 5 m/s^2 to get 200 m?

     Given:    a = 5 m/s^2

                    s  = 200 m

                   hidden given:  vi = 0   starting at rest

     Asked:    t  =  ?

    Solution:

             x  =   vi * t   +   1/2 ( at^2 )    Applicable equation with have a and s.

             since  vi = 0,

             x  = 1/2 at^2

            200 =  1/2 ( 5 ) t^2

             t  = 9 sec.

2)  A rock is dropped at 30 m/s. How high is the cliff?

     Given:     vf  = 30/s

                     hidden given:   vi =  0 

     Asked:     s  =  ?    or   height h = ?

     Solution:

                   vf^2  -  vi^2  =  2 a s 

                   Since this is free fall, a = g   which is 9.8 m/s

                    vf^2 -  vi^2  =  2 (-g) h

                    h  =    v i^2 /  (2g)

                    h  =  (30)^2 / 2 (-g)

                    h  =  45  m/s

3)  A stone is thrown horizontally at vi = 30 m/s. What is the total speed after 4 sec.

     speed?   

     Given:   vi = 30 m/s

                    t  = 4 sec

                   hidden given:  projectile motion (throwing horizontally)

                                           still use   a or  g =  -9.8 m/s^2 

     Asked:   Total speed,  needs also  vf = ?

      Solution:  Since speed,  vf =  g *  t

                       At t = 4 with g = 9.8 m/s^2,       vf  =  40 m/s

                     total speed =   vi  +  vf

                                       =   30 m/s  +  40 m/s

                     total speed  =   70  m/s

                           

  4) A race car starts at a = 5 m/s^2.  What is velocity after 1.0 x 10^2 ft or 100 ft? How much time?

     

       Given:    a  = 5 m/s

                      s2 = 100 ft  or 30.2  m/s

                      hidden given:  vi  = 0   since car starts at rest

       Asked :   vf  =  ?     t  = ?

       Solution:

                     vf^2  -  vi^2  =  2 

                     vf^2    =  2 (5)(30 m/s)   =  300

                     vf        =   17.32   m/s

                     v  =   vo  +  at

                     17.32  =   (5) t

                        t  =     3.4 sec

Additional example:

A soccer ball at rest is kicked with vf = 10 m/s  t 30 degrees.   Calculate time.

First, list down all the given and unknown

     vi = 10 m/s

     hidden given:  from ball at rest,  vi = 0

     hidden constant for projectile motion:     a  or g  =  9.8 m/s^2

     t   =  2 ( v /  a )     but in this case a = g

     t    =   2 v sin (theta) / g       (for projectile)

     t  = 1.01  sec

 Kinematics is indeed a challenging subject to handle, but we can manage if we understand how it was derived to form all equations. 

     

         

     

Understanding Residential Wiring

Imagine we are living a century ago when Thomas Edison and Nikola Tesla were only starting their discoveries on AC and DC.

We would have a hard time adjusting. We would only be using candles and fires for light. We would have to chop woods to cook for food.We would have to spend hours just doing our home chores since appliances since we would not have appliances and electrical machines doing the jobs for us.

We are really lucky today to receive all the benefits of the hardwork of our scientists before.

Now, with only one click on the switch, we have our lights on. With one press on remote control, we have our TV shows displayed in front of us. With one push on electric fans switch, we have automatic fan running to fight the heat and with only few settings for washing machine, we have all our laundries done without any effort.
Our power supply comes very convenient to us nowadays and is one of the everyday necessities we have. In this regard, it is also important to at least be able to recognize the components of our electrical system. Aside from the series of wires on mind, being aware of its other components is also important and can be very helpful during emergencies.

 

• Electric meters - From the pole where our transformers are, the wiring are then connected to a an electric meter located near our homes for the power consumption monitoring. Our Electric Cooperative staff usually has to seal this meter to prevent any illegal connection such as inserting jumper wire so that the meter will be bypassed. In the Philippines, electric meter is located just before Service Entrance. However, in other countries like US, it is usually common to see the Service Entrance first on the top before the meter.

• Service Entrance - This  should also be familiar to a homeowner. This serves as the Connection and Disconnection point of electricity from electric company to the houses. We can see service entrance as joint for two wires from the transformer going to our Electric panel. If we are not able to pay electrical bills, then Electric Cooperative staff will just have to locate it and disconnect power from there.

• Electrical Panel Board - We rarely think about this one until power goes out in the kitchen because we turned on our water heater or until our house has all circuits tripped just after turning on an AC Unit. Once or twice a year, we visit our home's panel board because of emergencies. All of a sudden, it becomes important. Oftentimes it is also either poorly marked or there is no directory at all. If it is the Main breaker that goes off, the electrician or the person in charge has to shut down and reset the breakers one at a time during troubleshooting.

• In some residential designs, we have Isolator Circuit breaker in an Enclosure for convenience. Then the electrician just makes use  of main lugs  in the panel board so that the cable can be connected to the circuit breakers through the busbars. There is also a Ground bus or Ground Screw for the grounding wire. Panel boards have also a deadfront, a GI sheet, to cover wires and protect users from any electrical conductors.

• Outlets - These are where we insert of appliances' plugs. They can come as two-prong or three-prong type latter is also referred to as Ground Circuit Fault Interrupter (GFCI). It can also be indoor or outdoor type. Outdoor type or weatherproof outlets have enclosures. In our electrical standard, a circuit can have up to 10 - 12 circuit depending on the design. Our electrical code states that there should be at least 12 feet distance between outlets. However, in common homes, 6 feet is already an average distance.

 

Motor Control Starter Basics (Direct-On-line)

The term "Motor Control Starter" is actually confusing for some people. Technically, the main purpose ng motor starter is not to start the motor, but to let motor start and run without damage.
The term starter is based only on the overload relay that is used to protect the motor from starting current.

In simplest form, motor control starter can be seen in a Direct-On-Line circuit which is composed of MCCB, Magnetic Contactor and Overload Relay.

1)  Molded Case Circuit Breaker (MCCB) - Ang circuit breaker ay may tatlong functions: (a) Isolator, (b) Proteksyon a circuit sa Overload, Grounding at Short Circuit (c) Switching purposes. Sa Control Panel, nasa itaas ang breaker dahil ito ang unang main protection na kakailanganin sa motor. In case may exposed wires na nagcause ng electrical leak o short circuit, agad agad itong magtritrip.

 Kadalasan din itong ginagamit para mahiwalay ang power supply sa motor sakali may preventive or corrective maintenance na gagawin.

2)  Magnetic Contactor  - Ang magnetic contactor ay isang klase ng relay na ginagamit para sa frequent switching ng isang circuit.  Para lang itong "pinalaki na auxiliary relay" - may electromagnectic coil at nagproprovide ng karagdagang contacts sa circuit para sa ON-OFF mode.

Importante ito sa Motor Control.  As per definition ng mga nauna kong articles, ang relay ay power device na kayang kontrolin ang mas mataas na boltahe. Sa concept ng magnetic contactor, halimbawa, ang may 24VAC coil na contactor ay pwedeng kontrolin ang mas mataas na 220 VAC switched circuit. Dahil sa magnetic contactor,  naging posible din kabitan ng ibang mas maliliit na devices para sa motor.  (For instance, ikonekta lang sa contactor ang ilang auxiliary relays at pwede nang lagyan ng karagdagang pushbuttons, pilot led lights at selector switches)

Ang magnetic contactor ay gamit para sa Manual Control or Automatic Control System.

Paano naman ito gagana? Simple lang. Ang Contactor sa Direct-on-line ay nasa Normally Open (N.O) na position. Pag dadaan ang current sa coil (or maenergize ang coil sa technical term), ang contacts na magkahiwalay ay magdidikit, magcloclose ang circuit at mag-Start ang motor.

3) Overload Relay - Sa baba ng magnetic contactor ang overload relay. Ipinapares  ito sa magnetic contactor pasa sa Overload Protection. Ang OL Relay ay hinahayan ang mga short current overloads na dumadaan sa motor sa unang andar nito ngunit automatic na nagtritrip pag naging tuloy-tuloy ang overload current.

Sa principle ng magnetic induction, ang isang motor ay kailangan ng malakas na current para maset up ang electromagnetic field. Ibig sabihin, isang malakas sa sipa ng kuryente muna, para mapaandar ang motor. Ang disadvantage dito, pag parati itong mangyayari, madaling mag-iinit ang motor na pwede ikasira kaagad nito.

Ang overload relay ang solusyon sa isyu ng high starting torque. Dahil dito, naging posibleng gamitin ang motor nang hindi nasisira kaagad. Naiiwasan nating maoverheat ang motor. In short, iwas sunog sa motor windings.

Additional notes:

• Magnetic Contactor + Overload Relay = Motor Starter. Ang simpleng motor starter ay kailangan lang ng dalawang devices.  Kaya lang, walang kakayahan ang magnetic contactor na magcause ng power intteruption sa tuwing may short circuit. Dito pumapasok ang MCCB.

•  Molded Case Circuit Breaker + (Magnetic Contactor + Overload Relay) = Combination Magnetic Starter