1 1 ECET 211 Electric Machines & Controls Relays Text Book: Electric Motors and Control Systems, by Frank D. Petruzella, published by McGraw Hill, 2015. Paul I-Hai Lin, Professor Electrical and Computer Engineering Technology P.E. States of Indiana & California Dept. of Computer, Electrical and Information Technology Purdue University Fort Wayne Campus Prof. Paul Lin Lecture 7 Relays Part 1. Electromechanical Control Relays • Relay Operations • Relay Applications • Relay Styles and Specifications Part 2. Solid State Relays • Operation • Specifications • Switching Methods Part 3. Timing Relays • Motor-Driven Timers • Dashpot Timers • Solid-State Timing Relays • Timing Functions Prof. Paul Lin 2 Part 4. Latching Relays • Mechanical Latching Relays • Magnetic Latching Relays • Latching Relay Application • Alternating Relays Part 5. Relay Control Logic • Control Circuit Inputs and Outputs • AND Logic Function • OR Logic Function • Combinational Logic Functions • Not Logic Function • NAND Logic Function • NOR Logic Function
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ECET 211 Electric Machines & Controls
Relays
Text Book: Electric Motors and Control Systems, by Frank D. Petruzella, published by McGraw Hill, 2015.
Paul I-Hai Lin, Professor
Electrical and Computer Engineering TechnologyP.E. States of Indiana & California
Dept. of Computer, Electrical and Information Technology
Purdue University Fort Wayne Campus
Prof. Paul Lin
Lecture 7 Relays
Part 1. Electromechanical Control Relays
• Relay Operations
• Relay Applications
• Relay Styles and Specifications
Part 2. Solid State Relays
• Operation
• Specifications
• Switching Methods
Part 3. Timing Relays
• Motor-Driven Timers
• Dashpot Timers
• Solid-State Timing Relays
• Timing Functions Prof. Paul Lin 2
Part 4. Latching Relays
• Mechanical Latching Relays
• Magnetic Latching Relays
• Latching Relay Application
• Alternating Relays
Part 5. Relay Control Logic
• Control Circuit Inputs and Outputs
• AND Logic Function
• OR Logic Function
• Combinational Logic Functions
• Not Logic Function
• NAND Logic Function
• NOR Logic Function
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Part 1. Electromechanical Control RelaysRelay Operations
Electromagnetic Relay – a switch that is operated by an electromagnet
Two parts of Electromechanical Control Relay (Figure 7-1):
• Coil input (control circuit)
• Contacts output (Load circuit)
Used to control small load of 15A or less
Applications
• Control coils in motor contactors and starters
• Switching solenoids, pilot lights, audible alarm, and small motor (1/8 hp or less)
Prof. Paul Lin 3
Part 1. Electromechanical Control RelaysRelay Operations
Figure 7-2 Relay coil and contacts
Prof. Paul Lin 4
Typical Relay Applications: One relay controls multiple pilot lights
Figure 7-3 Relay coil and contacts – CR1, CR2
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Part 1. Electromechanical Control RelaysRelay Applications
Current or signal amplification (small signal current => control large load current)
Control high-voltage load: 12 V => 480V load
Figure 7-4 Relay used to control a high-voltage
Prof. Paul Lin 5
Control high-current load
Figure 7-5 Using a relay to control a high-current load circuit with a low-current control circuit