Difference between Miniature Circuit Breaker (MCB) and Molded Case Circuit Breaker (MCCB)
Tuesday, February 21, 2017
Monday, February 20, 2017
About Magnetic contactor
ম্যাগনেটিক কন্ট্রাক্টর এমন একটি বৈদ্যুতিক ডিভাইস যা লোডের নিয়ন্ত্রন, অটোমেশন, রক্ষানাবেক্ষনের কাজে ব্যবহৃত হয়ে থাকে। এটি অনেকটা ম্যাগনেটিক রিলের মতই। তবে রিলে সাধারনত লো পাওয়ার ও ভোল্টেজে ব্যবহৃত হয় অন্য দিকে হাই পাওয়ারের কথা চিন্তা করলে হেভি ডিউটি সম্পন্ন এসব কন্ট্রাক্টরের কথাই শুধু মাথায় আসে। নিম্নে এর গুরুত্বপূর্ণ অংশ গুলো সংক্ষেপে অালোচনা করা হলো......
#মেইন_কন্টাক্ট
এটা মুলত পাওয়ার কে সুইচিং এর মাধ্যমে লোড অন এবং অফের কাজ করে থাকে। এতে ৩ টি টার্মিনাল থাকে যার ইনপুট গুলো কে L1, L2, L3 এবং আউটপুট গুলো কে T1, T2, T3 অাকারে প্রকাশ করা হয়।
#অক্সিলারি কন্টাক্ট
অক্সিলারি কন্টাক্ট কে ব্যবহার করে লোড কে অটোমেশন মুডে বা প্রোটেকশন এর সার্কিট তৈরি করা হয়। এতে দুই ধরনের টার্মিনাল থাকে
১) নরমালি ওপেন (NO) 2) নরমালি ক্লোজড (NC)
#কয়েল
কয়েল গুলো ইলেকট্রোম্যাগনেট সৃষ্টি করতে সক্ষম, এতে পাওয়ার সাপ্লাই দিলে এটি এনার্জাইজড হয়ে চুম্বক এ পরিনিত হয়ে মেইন কন্টাক্ট গুলোকে নরমালি অপেন কন্ডিশন থেকে ক্লোজড কন্ডিশনে আনে। কয়েলে প্রয়োগকৃত ভোল্টেজ গুলো নিম্ন রুপ হতে পারে.... 6v Dc, 12v Dc, 24v Dc এবং 110v Ac,250v Ac, 450v Ac
সাধারনত কয়েলের টার্মিনাল দুটো কে A1 এবং A2 দ্বারা চিহ্নিত করা থাকে।
#অক্সিলারি_ব্লোক
অক্সিলারি কে সংযুক্ত করতে এতে অক্সিলারি ব্লোক থাকে। এ অক্সিলারি ব্যবহার করে অতিরিক্ত NO & NC টার্মিনাল তৈরি করে নেওয়া যায়।
Figure (1): Magnetic contactor
Figure (2): Magnetic contactor
Saturday, February 18, 2017
Basic of PLC
A Programmable Logic Controller is a device that a user can program to perform a series or sequence of events. These events are triggered by stimuli (called inputs) received at the programmable logic controller through delayed actions such as time delays or counted occurrences.
Once an event triggers, it actuates in the outside world by switching on or off electronic control gear or the physical actuation of devices. A Programmable Logic Controllers will continually loop through its user defined program waiting for inputs and giving outputs at the specific programmed times.
As you would imagine in the world of computers they have their own language. This language is used to program the Programmable Logic Controller can be used in three formats, ladder, instruction list and logic symbol. More about this a bit later on.
Programmable Logic Controllers first came about as a replacement for automatic control systems that used tens and hundreds (maybe even thousands) of hard wired relays, motor driven cam timers and rotary sequencers.
More often then not, a single PLC can be programmed to replace thousands of relays and timers. These Programmable Logic Controllers were first befriended by the automotive manufacturing industry, this enabled software revision to replace the laborious re-wiring of control panels when a new production model was introduced.
Many of the earliest Programmable Logic Controllers expressed all decision making logic in a program format called Ladder Logic, which from its appearance was very similar to electrical schematic diagrams.
This of course was perfect for the electricians of the day, whom quite able to follow and trace out circuit problems with electrical schematic diagrams.
So using ladder logic became second nature to them allowing the electricians an relatively easy transition from hard wired circuits to software driven circuits.
This is the reason this program notation was chosen, to reduce training time for the existing technicians. Other early Programmable Logic Controllers used an instruction list type form of programming, based on a stack-based logic solver. Which was far most difficult to master.
So, what’s a Program?
I’m glad you asked!
A program is a connected series of instructions written in a language that the Programmable Logic Controller can understand. There are three forms of program format for PLC’s these are Ladder, Instruction and SFC/STL. Not all programming tools can work with all programming formats.
Generally hand held programming panels only work with instruction format while most graphic programming tools work with both instruction and ladder format. Specialist programming software will also allow SFC style programming but that’s for another time.
We will only be concerning ourselves with Ladder Logic programming here, because it's the most widespread in use today, probably because it's the easiest to grasp and get into the quickest.
Now, there's one big difference between a PLC and a PC type computer; as mentioned above, they only have one program to run. Unlike the PC, which is capable of running several programs at once within the Windows framework. Any of these could one or many many more of the different programs that could be installed on the PC. Why? In one word, speed.
A PLC will be designed to run its one program at a very fast speed, only branching out from within the main bit when an event happens. Events that happen in real time. This gives our little PLC beastie the ability to respond very quickly to any of the events under its control via an input.
Its response would then be carried out via an output. For example controlling a machines production running at 30,000 units an hour! Such as an offset web printing press churning out newspapers or book pages.
Ladder Logic, (the PLC programming language) is very closely associated to relay logic. In relay logic there are both contacts and coils that can be loaded and driven in different configurations. As there are in ladder logic, but a lot more configurations are possible. However the basic principal remains the same.
The program is written to switch the desired outputs for a given set of inputs energized. The 'hello world' program equivalent for a PLC would be a light bulb and a switch (see below). The switch is the input and the bulb would be controlled by the output. So, when the switch (input) is on, the bulb (output) is on.
A coil (relay logic terminology) drives outputs of the PLC (a ‘Y’ device, e.g. Y01) or drives internal coils (‘M’ device) timers, counters or flags. Each coil has associated contacts. These contacts are available in both normally open (NO) and normally closed (NC) configurations.
The term normally refers to the status of the contacts when the coil is not energized. Using a relay analogy, when the coil is off, a NO contact would have no current flow, that is, a load being supplied through a NO contact would not operate. However, a NC contact would allow current to flow, hence the connected load would be active.
Activating the coil reverses the contact status, that is, the current would flow in a NO contact and a NC contact would then inhibit the flow.
Physical inputs to the PLC (X devices) have no programmable coil. These devices may only be used in a contact format, again with NO and NC types available.
Because of the close relay logic association, ladder logic programs can be read as current flowing from the left vertical line to the right vertical line. This current must pass through the input (switch) configuration in order to switch the output coil Y0 on.
Therefore in the example below, switching X0 on and X1 being off would causes the output Y0 to also to switch on. However, if X1 were to switch on while X0 was on, the output coil would then switch off.
This is a very basic example of course, as they are very capable of automating a complete warehouse or running very complex machines on their own.
Then, as you would imagine, the program it would be running would have many twists and turns to respond to the 10's and quite possibly even 100's of inputs and outputs. These inputs in conjunction with the program would be dictating the on and off pattern of the outputs at any given time.
Here are just a few examples of PLC programming applications that have been successfully completed and are in use today.
A Programmable Logic Controller is a device that a user can program to perform a series or sequence of events. These events are triggered by stimuli (called inputs) received at the programmable logic controller through delayed actions such as time delays or counted occurrences.
Once an event triggers, it actuates in the outside world by switching on or off electronic control gear or the physical actuation of devices. A Programmable Logic Controllers will continually loop through its user defined program waiting for inputs and giving outputs at the specific programmed times.
As you would imagine in the world of computers they have their own language. This language is used to program the Programmable Logic Controller can be used in three formats, ladder, instruction list and logic symbol. More about this a bit later on.
Programmable Logic Controllers first came about as a replacement for automatic control systems that used tens and hundreds (maybe even thousands) of hard wired relays, motor driven cam timers and rotary sequencers.
More often then not, a single PLC can be programmed to replace thousands of relays and timers. These Programmable Logic Controllers were first befriended by the automotive manufacturing industry, this enabled software revision to replace the laborious re-wiring of control panels when a new production model was introduced.
Many of the earliest Programmable Logic Controllers expressed all decision making logic in a program format called Ladder Logic, which from its appearance was very similar to electrical schematic diagrams.
This of course was perfect for the electricians of the day, whom quite able to follow and trace out circuit problems with electrical schematic diagrams.
So using ladder logic became second nature to them allowing the electricians an relatively easy transition from hard wired circuits to software driven circuits.
This is the reason this program notation was chosen, to reduce training time for the existing technicians. Other early Programmable Logic Controllers used an instruction list type form of programming, based on a stack-based logic solver. Which was far most difficult to master.
So, what’s a Program?
I’m glad you asked!
A program is a connected series of instructions written in a language that the Programmable Logic Controller can understand. There are three forms of program format for PLC’s these are Ladder, Instruction and SFC/STL. Not all programming tools can work with all programming formats.
Generally hand held programming panels only work with instruction format while most graphic programming tools work with both instruction and ladder format. Specialist programming software will also allow SFC style programming but that’s for another time.
We will only be concerning ourselves with Ladder Logic programming here, because it's the most widespread in use today, probably because it's the easiest to grasp and get into the quickest.
Now, there's one big difference between a PLC and a PC type computer; as mentioned above, they only have one program to run. Unlike the PC, which is capable of running several programs at once within the Windows framework. Any of these could one or many many more of the different programs that could be installed on the PC. Why? In one word, speed.
A PLC will be designed to run its one program at a very fast speed, only branching out from within the main bit when an event happens. Events that happen in real time. This gives our little PLC beastie the ability to respond very quickly to any of the events under its control via an input.
Its response would then be carried out via an output. For example controlling a machines production running at 30,000 units an hour! Such as an offset web printing press churning out newspapers or book pages.
Ladder Logic, (the PLC programming language) is very closely associated to relay logic. In relay logic there are both contacts and coils that can be loaded and driven in different configurations. As there are in ladder logic, but a lot more configurations are possible. However the basic principal remains the same.
The program is written to switch the desired outputs for a given set of inputs energized. The 'hello world' program equivalent for a PLC would be a light bulb and a switch (see below). The switch is the input and the bulb would be controlled by the output. So, when the switch (input) is on, the bulb (output) is on.
A coil (relay logic terminology) drives outputs of the PLC (a ‘Y’ device, e.g. Y01) or drives internal coils (‘M’ device) timers, counters or flags. Each coil has associated contacts. These contacts are available in both normally open (NO) and normally closed (NC) configurations.
The term normally refers to the status of the contacts when the coil is not energized. Using a relay analogy, when the coil is off, a NO contact would have no current flow, that is, a load being supplied through a NO contact would not operate. However, a NC contact would allow current to flow, hence the connected load would be active.
Activating the coil reverses the contact status, that is, the current would flow in a NO contact and a NC contact would then inhibit the flow.
Physical inputs to the PLC (X devices) have no programmable coil. These devices may only be used in a contact format, again with NO and NC types available.
Because of the close relay logic association, ladder logic programs can be read as current flowing from the left vertical line to the right vertical line. This current must pass through the input (switch) configuration in order to switch the output coil Y0 on.
Therefore in the example below, switching X0 on and X1 being off would causes the output Y0 to also to switch on. However, if X1 were to switch on while X0 was on, the output coil would then switch off.
This is a very basic example of course, as they are very capable of automating a complete warehouse or running very complex machines on their own.
Then, as you would imagine, the program it would be running would have many twists and turns to respond to the 10's and quite possibly even 100's of inputs and outputs. These inputs in conjunction with the program would be dictating the on and off pattern of the outputs at any given time.
Here are just a few examples of PLC programming applications that have been successfully completed and are in use today.
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