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E3065/02/1 SWITCH
SWITCH
OBJECTIVES
General objective : To understand the concept and basic application of a switch.
Specific objectives : At the end of the unit you should be able to: Identify the basic function of switch . Identify the type of switches. Describe the application of switch in industrial. Draw the symbol of a switch.
UNIT 2
E3065/02/2 SWITCH
2.1 INTRODUCTION OF SWITCH.
The switch is a mechanical, electrical or electronic device that opens or close a circuit. Switching may also be called making or breaking the circuit.
2.2 BASIC FUNCTION OF SWITCH AND SWITCH DIAGRAM.
The switches function as a device that opens or close a circuit. The closing of a switch is called making the circuit. The opening of switch is called breaking the circuit. The output of system depends on the switching pattern of the converter switches and the input voltage (or current). Similar to the linear system, the output quantities of a converter can be expressed in terms of input quantities, by spectrum multiplication. The arrangement of single –phase diagram of converter and simple hold circuit are shown in figure 2.2(a) and 2.2(b) below.
Figure 2.2(a): Single-Phase Diagram Of Converter Structure.
INPUT
E3065/02/3 SWITCH
Figure 2.2(b): Simple Sample And Hold Circuit.
2.3 TYPE OF STRUCTURE AND CONSTRUCTION OF SWITCH
The structure and construction of power electronics switch can divided into four parts:
i. Design of power circuits.ii. Protection of power devices.iii. Determination of the control strategy.iv. Design of logic and gating circuits
In the analysis, the power devices are assumed to be ideal switches unless stated otherwise; and effects of circuit stray inductance, circuit resistances, and source inductance are neglected. The practical power devices and circuit are also affected. However, in the early stage of design, the simplified analysis of circuit is very useful to understand the operation of the circuit and to establish the characteristics and control strategy.
Before a prototype is built, the designer should investigate the effects of the circuit parameters (and devices imperfections) and should modify the design if necessary. Only after the prototype is built and tested, the designer can be confident about validity of the design and can estimate more accurately some of the circuit parameters (e.g., stray inductance).
E3065/02/4 SWITCH
Activity 2A
TEST YOUR UNDERSTANDING BEFORE YOU CONTINUE WITH THE NEXT INPUT…!
2.1 Explain what is the meaning of switch.
2.2 What is the type of structure and construction that should be considered before designing a circuit?
Hii !!!!!…..Good Luck and Try your best ….
E3065/02/5 SWITCH
Feedback To Activity 2A
2.1 The switch is a mechanical or electrical device that opens or close a circuit. Switching may also be called making or breaking the circuit.
2.2 The structure and construction of power electronics switch can divided into four parts:
i. Design of power circuits.ii. Protection of power devices.iii. Determination of the control strategy.iv. Design of logic and gating circuitsv. The power devices are assumed to be ideal switches unless stated otherwise; and
effects of circuit stray inductance, circuit resistances, and source inductance are neglected.
vi. The nearly stage of design, the simplified analysis of circuit is very useful to understand the operation of a the circuit and to establish the characteristics and control strategy.
vii. The designer should investigate the effects of the circuit parameters (and devices imperfections) and should modify the design if necessary.
viii. The designer can be confident about validity of the design and can estimate more accurately some of the circuit parameters.
E3065/02/6 SWITCH
2.4 TYPES OF SWITCH
There are many different type of switches. Some switch types are push buttons, limit switch, slide switch, rocker switch, precision switch and toggle switch.
2.4.1 PUSH BUTTONS SWITCH.
A pushbutton is a switch activated by finger pressure. Two or more contacts open or close when the button is depressed. Pushbuttons are usually spring loaded so as to return to their normal position when pressure is removed. Figure 2.4(a), show that the mechanical-interlocked pushbutton with NO (normally open) and NC (normally close) contacts, rated to interrupt an ac current of 6A one million times.
INPUT
E3065/02/7 SWITCH
Figure 2.4(a): Mechanical-Interlocked Pushbutton
2.4.2 LIMIT SWITCH
A limit switch is a low-power snap-action device that opens or closes a contact, depending upon the position of mechanical part. Other limit switches are sensitive to pressure, temperature, liquid level, direction of rotation and so on. Figure 2.4(b) show that the limit switch with one NC contact, rated for ten million operations, position accuracy is 0.5 mm.
Figure 2.4(b): A Limit Switch.
2.4.3 SLIDE SWITCH.
E3065/02/8 SWITCH
A slide switch is a switch activated by sliding of two or more contacts open or close when the button is depressed. Pushbutton are usually spring loaded so as to return to their normal position when pressure is removed. Figure 2.4(c), show that the mechanical-interlocked sliding plate/rod with NO (normally open) and NC (Normally close) contacts.
Figure 2.4(c): Schematic And Symbol Of Slide Switch.
2.4.4 ROCKER SWITCH.
A rocker switch is a switch activated by 3 finger which includes 2 finger push button for opening and closing of 2 circuits. Two contacts open or close for 2 circuits when the button are pressed and depressed. Pushbutton are usually spring loaded in the bottom to return to their normal position when pressure is removed. Figure 2.4(d), show that the mechanical-interlocked
E3065/02/9 SWITCH
pushbutton with ON (normally open) and NC (Normally close) contacts through 2 circuit involved.
Figure 2.3(d): Schematic And Symbol Of Rocker Switch.
2.4.5 PRECISION SWITCH.
A precision switch is a switch activated by roller loaded on the top of pushbutton to open or close a circuit. Only one contact open or close when the button is depressed by load moving on top of the roller. Pushbutton are usually spring loaded so as to return to their normal position when load on top of roller is removed. Figure 2.4(e), show that the mechanical-interlocked pushbutton with ON (normally open) and NC (Normally close) contacts, rated to interrupt an ac current of mechanical effect to the top of roller device.
E3065/02/10 SWITCH
Figure 2.4(e): Schematic And Symbol Of Precision Switch
2.4.6 TOGGLE SWITCH.
A toggle switch is a switch activated by ball bearing moving for open or close a circuit. The movement of roller makes a contact to open or close a circuit when the toggle is depressed. A toggle usually parallel with the force loaded so as to open or close. Figure 2.4(f), show that the mechanical-interlocked toggle pushbutton with NO (normally open) and NC (Normally close) contacts.
Figure 2.4(f): A Toggle Switch
E3065/02/11 SWITCH
2.5 PRINCIPLE OPERATION OF SWITCH
Switches should follow the international system of units (SI) which defines the ampere (the fundamental unit of electric current) as the constant current which, if maintained in two straight parallel contactors of infinite length and negligible circular cross section place in a mechanism part that will produce a force between two parallel contactors.
By international agreement, the value of the international ampere for switches was based on the electrolytic deposition of silver form a silver nitrate solution. The resistance standard of switches is absolute measurement of the ohm and is carried out by the international standards laboratories, which preserve a group of primary resistant standard. For the voltage standard the saturated cell has a temperature dependence, and the out put voltage change about -40 V/0C from the nominal 1.0185 V.
The output of a converter depends on the switching pattern of the converter switches and the input voltage (on current). Similar to linear system, the output quantities of a converter can be expressed in terms of the output quantities, by spectrum multiplication.
E3065/02/12 SWITCH
Activity 2B
TEST YOUR UNDERSTANDING BEFORE YOU CONTINUE WITH THE NEXT INPUT…!
2.3 List FOUR types of switches and describe the function of each switch listed.
2.4 Describe briefly the standard and operation of switch.
Hii !!!!!…..Good Luck and Try your best ….
E3065/02/13 SWITCH
Feedback To Activity 2B
2.3 Four types of switches;
i. PUSH BUTTONS SWITCH.A pushbutton is a switch activated by finger pressure. Two o more contacts
open or close when the button is depressed. Pushbutton are usually spring loaded so as to return to their normal position when pressure is removed.
ii. LIMIT SWITCHA limit switch is a low-power snap-action device that opens or closes a contact,
depending upon the position of mechanical part. Other limit switches are sensitive to pressure, temperature, liquid level, direction of rotation and so on.
iii. SLIDE SWITCH.A slide switch is a switch activated by sliding of two or more contacts open or
close when the button is depressed. Pushbutton are usually spring loaded so as to return to their normal position when pressure is removed.
iv. TOGGLE SWITCH.A toggle switch is a switch activated by ball bearing moving for open or close a
circuit. The movement of roller make a contact to open or close a circuit when the toggle is depressed. A toggle usually parallel with the force loaded so as to open or close.
v. PRECISION SWITCH.
E3065/02/14 SWITCH
A precision switch is a switch activated by roller loaded on the top of pushbutton to open or close a circuit. Only one contact open or close when the button is depressed by load moving on top of the roller. Pushbutton are usually spring loaded so as to return to their normal position when load on top of roller is removed.
2.4 Standard and operation of switch;
a. Switches should follow the international system of units (SI) defines the ampere (the fundamental unit of electric current) as the constant current which, if maintained in two straight parallel contactors of infinite length and negligible circular cross section place in a mechanism part that will produce a force between two parallel contactors.
b. The value of the international ampere for switches was based on the electrolytic deposition of silver form a silver nitrate solution.
c. The resistance standard of switches is absolute measurement of the ohm is carried out by the international standards laboratories, which preserve a group of primary resistant standard. For the voltage standard the saturated cell has a temperature dependence, and the out put voltage change about -40 V/0C from the nominal 1.0185 V.
d. The output of a converter depends on the switching pattern of the converter switches and the input voltage (on current). Similar to linear system, the output quantities of a converter can be expressed in terms of the output quantities by spectrum.
E3065/02/15 SWITCH
SELF-ASSESSMENT
Question 2-1
a. Describe briefly the principle operation of switch.
b. List THREE types of switches application in industries.
c. Describe the operation of each type the switch listed above.
Question 2-2
a. Draw the symbol of push button, limit and slide switch.
b. Sketch and describe the simple circuit for sample and hold circuit.
E3065/02/16 SWITCH
Feedback To Self-Assessment
Answer 2-1
a. The pushbutton switch (or limit switch, slide switch, rocker switch, precision switch and toggle switch) is a mechanical or electrical device that opens or close a circuit. Switching may also be called making or breaking the circuit. A pushbutton is a switch activated by finger pressure. Two o more contacts open or close when the button is depressed. Pushbutton are usually spring loaded so as to return to their normal position when pressure is removed.
b. There are many different type of switches used in industries. Same switch types are push buttons, limit switch, slide switch, rocker switch, precision switch and toggle switch. (choose (3) of switches given)
c. Choose (3) of below answers.
PUSH BUTTONS SWITCH.A pushbutton is a switch activated by finger pressure. Two o more
contacts open or close when the button is depressed. Pushbutton are usually spring loaded so as to return to their normal position when pressure is removed.
LIMIT SWITCHA limit switch is a low-power snap-action device that opens or closes a
contact, depending upon the position of mechanical part. Other limit switches are sensitive to pressure, temperature, liquid level, direction of rotation and so on.
E3065/02/17 SWITCH
SLIDE SWITCH.A slide switch is a switch activated by sliding of two or more contacts
open or close when the button is depressed. Pushbutton are usually spring loaded so as to return to their normal position when pressure is removed.
TOGGLE SWITCH.A toggle switch is a switch activated by ball bearing moving for open or
close a circuit. The movement of roller make a contact to open or close a circuit when the toggle is depressed. A toggle usually parallel with the force loaded so as to open or close.
PRECISION SWITCH.A precision switch is a switch activated by roller loaded on the top of
pushbutton to open or close a circuit. Only one contact open or close when the button is depressed by load moving on top of the roller. Pushbutton are usually spring loaded so as to return to their normal position when load on top of roller is removed.
E3065/02/18 SWITCH
Answer 2-2
a. Please refer to Input 2.4 for the answer.
b. For the sketch circuit, you can refer to figure 2.2(b).The explanation includes;
i. Its function as a device that opens or close a circuit. ii. The closing of a switch is called making the circuit. iii. The opening of switch is called breaking the circuit. iv. The output of system depends on the switching pattern of the converter
switches and the input voltage (or current). v. Similar to the linear system, the output quantities of a converter can be
expressed in terms of input quantities, by spectrum multiplication
HAVE A FUN AND NICE DAY.
See you at the next section……..