ElectricalChile

Profiter L'Ingénierie



Learn and Understand Beginner Electrical Control Systems





OFF

Simulating Start/Stop with electrical retention


First, We must to know these concepts:

  • Contactor: is a Power Electromechanic Device used in Control Systems and when the Coil is energized it and his Contacts NO and NC work, this is energized by a Control Circuit, it's one of the most important devices using in Automation and Control Systems, Contactor is a element used for Power and Control

  • Control Wire: There are wire and connections used for "Activate" a Coil Contactor, in many wires we create the Control that finally Activate the Power

  • Power Wire: There are wire and connections used to Power devices as Motors, Pumps and Others, is not the same that "Control", Power will energize all depending "Control Wire"

  • Normally Open Contact (NO): There are Control Contacts, in his state "normal" as "Open", in normally conditionss the flow current will not energize because the road is "open", when Coil is activated, The Open Contact now is "Closed" and power flow, NO-NA Contacts are used mainly to energize Contactor Coils or Pilot Lights

  • Normally Closed Contact (NC): There are Control Contacts, in his state "normal" as "Closed", in normally conditions the flow current will energize because the road is "closed", when Coil is activated, The Closed Contact now is "Open" and power flow will not energize , NC Contacts are used mainly to Interlock Contactor Coils or similar control

  • Electrical Retention: This is a type of "electrical retention" used in Electrical Control System and it keeps the road flow current powering, if we don't have a retention the Status ON in 1 second will be OFF

Must Knowledge

Electricity
Basic English



MAIN SUMMARY
STEP 1: Differences Between Power and Control
STEP 2: Basic Elements Control System
STEP 3: Main Control Wire
STEP 4: Indicators Control
STEP 5: Fails Control
STEP 6: QUESTIONS & ANSWERS


STEP 1 : DIFFERENCES POWER AND CONTROL

Must to understand both concepts to start to learn Control System

Power Circuits:

  • Always is easier to wire
  • For these examples, Power is the wire that energize the Load
  • Circuits Power carry all Power (KW), that's the reason in high power facilities you can see thin cables and Robust Cables, one is Control and other is high Power
  • Contactor is one of the most used Components in Power and Controls, In the industries and medium facilities is the most common element found in Electromechanical

Control Circuits:

  • The wire is most difficult than Power Circuits
  • When you learn Control you must to understand what you are doing, can't have fails
  • Control Circuits mean work with elements as Pushbuttons, Emergency Stop, limit Switch, Switch, Contactors, Relays, and more
  • In conclusion, Control Circuits "Activate the Coil A1+A2 and power it in 220VAC" (Voltage differents in some countries) the Contactor Works and now Power Circuits pass through Contactor and energize the load connected down Contactor, when Coil is not activated, Power Circuit not energize
OFF

Simulating Start/stop with electrical retention in NO 13-14

AND WHAT HAPPENS IF WE DONT CONNECT "NO 13-14" with Pushbutton?

OFF

Simulating Start without retention

If we don't have connected the retention for our Control not works good in this case




STEP 2: COMMON ELEMENTS IN CONTROL

Let's see main elements used in Industrial Control Systems

Begin to learn too must to consider to know elements and devices

    POWER AND CONTROL DEVICES
  1. Contactores: Control and Power Device that allow or not that Flow Current activate the load, if his "Coil" is Activate the Power Flow trough it, is one of the most used components in Electromechanic, the coil is energized by some Voltages, 12-24-110-220-380 in VAC or VDC
  2. Electromechanical Relay: Electromechanical Device is "similar to Contactor", the Relay is used for low Power (W), Control some NO or NC, or to power Valves 12-24V (for not energize directly from electronic devices to the load)
  3. Impulse Relay (Telerruptor): Electromechanical Device used for Control and Power but mainly in One-Phase Loads, Impulse relay have a "Coil" that when is activated the power flow pass, the big difference is that Change State ON - OFF only with a "Push"
  4. Timers: Electronic devices that work in Time Function (s) and will active or not the power, in Control System the Timers work directly over "Coil" of a Contactor or Relay, of course passing through other Contactos NO or NC

    CONTROL AND ACTIVATION COMPONENTS
  1. Pushbutton Start/stop: Control Element that uses 1 NO (normally open) and green color to START; and 1 NC (normally closed) and red color to STOP
  2. Pushbuttons: Can find some different colors, are elementos using to Start (1NO - green) or Stop (1NC - red), practicly is the same that Start/Stop button, but pushbutton are installed independently
  3. Emergency Stop: His function is the same that all buttons, is you press it open or closed contacts, the majority of Emergency Stop uses 1NC that when we press it "Open Circuits" and stop retention or it keeps open and power flow can't pass when the emergency stop is activated (1NC when is activated is NO)
  4. Rotary Selector Switch: Too is a control element, but the differences with pushbuttons, Switch DONT need a electrical retention to activate, his mechanical form is different, when Selector is Turned the power flow throught and the one form to cut current, is turning switch to 0 position

    MOTOR PROTECCTION
  1. Thermal Overload Relay: There are one of the most used Motor protecction because is cheaaper and easy to install, then will see more examples how to use ti
  2. Asymmetric Relay: Device used to protect over "Overvoltage" ; "Low Voltages" ; "Fails in Outside Electrical System" ; too is very used but to use a Asymmetric relay is better have more knowledge and use it when is really necessary

    INDICATOR LIGHTS
  1. Light Pilots: There are elements that indicates via Lights when a element is energized, his use is in Three-Phase Indicators, Fails, ON-OFF Devices, you can install in 12-24-110 y 220 Volts

STEP 3: MAIN CONTROL WIRE

Let's learn the most important connections to understand Control Systems

PUSHBUTTON START-STOP WITH EMERGENCY STOP

Start (1NO) and Stop (1NC) with Emergency Stop (1NC) without retention, to activate 1 Contactor (K1)


OFF

The details of connections and wire are:



START 2 MOTORS SAME TIME WITH SAME BUTTONS AND STOP EMERGENCY

Start (1NO) and Stop (1NC) with Emergency Stop (1NC) without retention to activate 2 Contactors (K1-K2)


Electrical in Control Systems

The details of connections and wire are:

Electrical Control systems


START 2 MOTORS WITH INDEPENDENT BUTTONS AND EMERGENCY STOP

2 Start (1NO) and 2 Stop (1NC) with Emergency Stop (1NC) without retention to Activate 2 Motors independently each one (K1 and K2)



Industrial Electricity



STEP 4: INDICATORS WIRE

The next examples show how to work with indicators mainly Light Pilots


POWER BY START / STOP AND LIGHT PILOT TO "WORKING" AND "STOPPED"

1 Start (1NO) and 1 Stop (1NC) with Emergency Stop (1NC) without retention, to start a motor and light pilots show when it's stopped (reg light) or working (green light)



The details of connections and wire are:

How Electrical Control System works

POWER 2 MOTORS WITH INDEPENDENT BUTTONS AND EMERGENCY STOP

2 Start (1NO) and 2 Stop (1NC) with Emergency Stop (1NC) without retention to start 2 Motors and with Green Light Pilots working independently



Simulating Electrical Control Systems



STEP 5: WIRE AND CONTROL FAILS

Fails Control and Indicators support for a better Maintenance

START 1 MOTOR WITH BUTTONS, EMERGENCY STOP AND THERMAL OVERLOAD FAIL

1 Start (1NO) and 1 Stop (1NC) with Emergency Stop (1NC) without retention to Start 1 Motor with green light pilot while working and yellow pilot in case of "Fail"



Electrical Control System

IMPORTANT TO CONSIDER
  • Thermal Overload Relay works in different Current Ranges for example 1A-3A
  • Thermal Overload is the last vital protection for Motor, for this reason is very important select the right Thermal Overload (Right Current Protection), the tolerance maximum in a Motor must to be 20% over his Nominal Current and over that the Thermal Overload must to operate
  • In Fail Case (Overcurrent) Thermal Overload uses his contacts NC (95-96) what will open Circuit; and a Open Contact NO (97-98) that will close and will energize a Light Pilot that indicates the Thermal Overload has operated to protect and save the Motor
  • After Thermal relay has Operated, you must to "RESET" from same thermal overload, 95-96 (NC) back to closed and light Pilot connected to 97-98 (NO) will turn off

And How we wire a Three-Phase in Control System?

Electrical Control System

CONNECTING TWO MOTORS WITH START AND THERMAL OVERLOAD FOR EACH ONE

Electrical Control Systems

IMPORTANT CONSIDER:
  • In three-phase system the Circuit Breaker always must to be Three-phase protecction
  • In this schematic drawing, the Emergency Stop will stop both motors
  • The current in Circuit Breaker "3x10A" is just referential
  • If we understand perfectly above information, next step is know Advanced Electrical Control Systems and we are nearer to start to Program a PLC!

REVIEW ALL INFORMATION TO BE MORE CLEAR!

Know the difference between "Power" and "Control" in Industrial Electricity
Now know new elements as Contactors, Thermal Overload Relays, Buttons, Indicators, etc
Practically all schematics in Control Systems depend how are connected Normally Open (NO) and Normally Closed (NC) Contacts
You must to energize "Coil" (A1+A2) in Contactos for the Flow Power pass trough and energize the Load
When a Thermal Overload Relay operates for Overcurrent, the right connections and use is by NC 95-96 to open the circuit and for indicate we use NO 97-98 that close and energize pilot light "Fails", then to back to start relay must to "Reset" and his contact back to be normally NO and NC
We recommend you back to read, Control systems are "funnier" than "difficult"

s

QUESTIONS AND ANSWERS

HERE THE ANSWERS FOR YOUR QUESTIONS:

  1. How can begin to Understand Electrical Control Systems?
    First you must to know Electricity, it means understand when you connect, install eletrical cabinets, switch ladder 9/15, etc. knowing how the electricity carry energy, back to review STEP 1 HERE and will see the electricity being used to power other devices, control wire is "funny"

  2. Why a Rotary Switch doesn't need to be connected with "NO" contacts to have retention?
    Because the mechanical design of rotary switch is in the moment of TURN his design "is detained in the position", when we turn the contacts NO will close, for example a Rotatory Switch 1-0-2 (3 positions), in any of 3 positions is always keeping positions when you turn, a button is different because a "push" need a "electrical retention" to maintin the power flow passing

  3. Why at the moment of Push mi Pushbutton it connect but inmediatly it disconnect?
    When you push a button it may open or close circuits, in this case a start button use a open contact (NO) that when you press it close circuit and energize COIL, Why not has retention?Because is not connected with the NO Contacts (13-14 almot always), review the easy connection in STEP 1 HERE

  4. Which is the most used equipment in a design of a Simple Control System?
    Simple means, design a SStart/Stop with emergency stop and indicators for Working and Fail
    1. Three-pole Contactor with Coil 220V (depends voltage, remember may be 12-24-110-220-380) and 1NO (is obligation have a 1 open contact)
    2. Thermal Overload Relay 1NO + 1NC
    3. Button Start / Stop 1NO + 1NC
    4. Emergency Stop without retention 1NC
    5. Circuit Breaker Three-phase (power) and One-phase (control)
    6. Green Pilot Light 220V (working)
    7. Yellow Pilot Light 220V (fail)
    8. Control Cable for Phase and Neutral 18AWG
    9. Power cable depending of Power (KW) of the load
    10. Cable Ties
    11. Adhesive Cable Tie mounts
    12. Espiral Portacables
    13. Din Rail
    14. Slotted Wire Duct
    15. Electrical Cabinet (depends of the project)
    16. All projects are different, in this case we describe you some elements that is important always consider, remember in electrical industrial now we have started to work in Three-Phase Systems, Electrical Cabinets, Advanced Electricity, etc

  5. I Connected my Overload Thermal Realy directly after Contactor and it doesn't work, WHY?
    For the right operation in a Thermal Relay it must to use his Contacts NC(95-96) to open the circuit that energize Coil and NO(97-98) that indicates in a light the Thermal Overload has operated, Thermal Relay if only is connected in power, doesnt' work correctly, thermal overload must to work with his Contacts NO and NC