ECET 211 Electric Machines & Controls Lecture 7 Relays (1 of 2) Text Book: Electric Motors and Control Systems, by Frank D. Petruzella, published by McGraw Hill, 2015 Paul I-Hai Lin, Professor of 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 1 Part 1. Electromechanical Control Relays Relay Operations Relay Applications Relay Styles and Specifications Part 2. Solid State Relays Operation Specifications Switching Methods Motor-Driven Timers Dashpot Timers Solid-State Timing Relays Timing Functions Lecture 7 Relays 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 Prof. Paul Lin 2 1
Part 1. Electromechanical Control Relays Relay 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 Relays Relay Operations Figure 7-2 Relay coil and contacts Typical Relay Applications: One relay controls multiple pilot lights Figure 7-3 Relay coil and contacts CR1, CR2 Prof. Paul Lin 4 2
Part 1. Electromechanical Control Relays Relay 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 Control high-current load Figure 7-5 Using a relay to control a high-current load circuit with a low-current control circuit Relay: coil and contact Solenoid (2 A, 120V) Electronic parts: Diode, Transistor, Resistor (limit current) Prof. Paul Lin 5 Part 1. Electromechanical Control Relays Theory of Operation Figure 7-5 Control High Current Load Relay coil - on/off control by a power Transistor switch Relay switching on/off induced high Spike voltage e = - L Δi/Δt Transistor: Three terminal device: Collector, Emitter, Base Base input current 2 ma, Collector output current 20mA: a gain of 10 Diode (fast on/off switch) protecting transistor: fly wheeling diode turned-on, when VA VK 0.7 V Solenoid value current 2 A Total Current Gain = 2A/2mA = 1000 Prof. Paul Lin 6 3
Part 1. Electromechanical Control Relays Relay Styles and Specifications Figure 7-6 Plug-in style ice cube relay Figure 7-7 Relay manual push-totest button Figure 7-8 Typical DIN-rail with relays mounted Prof. Paul Lin 7 Part 1. Electromechanical Control Relays Relay Styles and Specifications Figure 7-9 Common relay contact switching arrangement Prof. Paul Lin 8 4
Operation Part 2. Solid State Relays Solid-State Relay (SSR) An electronic switch contains no moving parts Does not have coils and contacts Use semiconductor switching devices: Bipolar transistor, MOSFET, SCR, Triac Figure 7-10 Typical solid-state relay Prof. Paul Lin 9 Operation Part 2. Solid State Relays Figure 7-11 Optically coupled SSR used for AC load Figure 7-12 Optically coupled SSR used for DC loads Prof. Paul Lin 10 5
Demo Demo - Single-Phase Motor On/Off Control : SSR, Contactor, July 24 2015 Figure 1. AC Single-Phase Motor Demo (Circuit Drawings) Motor: 1/3 Hp, 115V, 60Hz, 5.2A, 1725 RPM (Split-phase with centrifugal switch) Magnetic switch (On/Off) Online Starter Computer Interface ready (through Solid State Relay - SSR: Input DC 3-32V) Prof. Paul Lin 11 Demo Demo - Single-Phase Motor On/Off Control : SSR, Contactor, July 24 2015 Figure 1. AC Single-Phase Motor Demo Motor: 1/3 Hp, 115V, 60Hz, 5.2A, 1725 RPM (Split-phase with centrifugal switch) Magnetic switch (On/Off) Online Starter Computer Interface ready (through Solid State Relay - SSR: Input DC 3-32V) Prof. Paul Lin 12 6
Demo Demo - Single-Phase Motor On/Off Control : SSR, Contactor, July 24 2015 Figure 1. AC Single-Phase Motor Demo Figure 2. Measurement of motor current using digital clamp ammeter. **** Clamp ammeter: Starting current 5.2A, and the no-load current is 4.3 A Prof. Paul Lin 13 Demo Demo - Single-Phase Motor On/Off Control : SSR, Contactor, July 24 2015 Figure 3 Measurement of VL, IL, Hz, Watt, kwh with a Kill A Watts power monitoring instrument, Line Voltage measurement - DMM, Line current measurement through a digital Camp meter (Starting and running current) (a) DMM line voltage measurement 122.3V, Power = 141 Watts, other measurement from Kill A Watt include VL = 122.5V, Frequency 59.9 Hz, PF = 0.22, P = 141 Watt, S = 546VA (b) Measured IL = 4.93A Prof. Paul Lin 14 7
Part 2. Solid State Relays Specifications Input voltage range: 5V DC to 24V DC, 32 V DC Output voltage range: 5V DC up to 480V AC Current rating: < 10A, up to 40 A, 50A (heat sink required) Figure 7-13 Multiple-pole SSR connections Prof. Paul Lin 15 Part 2. Solid State Relays Specifications Figure 7-13 Three-wire control utilizing a SSR and an SCR SCR (Silicon Control Rectifier) Prof. Paul Lin 16 8
Part 2. Solid State Relays Switching Methods Zero-switching relay (Zero crossing) Peak-switching relay Instant-on relay Thermal dissipation Leakage current Cost Figure 7-15 Zero Crossing SSR Prof. Paul Lin 17 Switching Methods Part 2. Solid State Relays Figure 7-16 SSR heat sink Loads more than 5A require a heat sink for reliable operation Figure 7-17 Electromechanical vs. SSR construction Prof. Paul Lin 18 9
Timing Relays An Introduction A time actuated control relay in which a fixed or adjustable time occurs after a change in the control signal before switching action occur. Enable a multitude of operation in a control circuit to be automatically started or stopped at different time intervals Figure 7-18 Timing relays Prof. Paul Lin 19 Motor-Driven Timers Figure 7-19 Synchronous clock timer Dashpot Timer Figure 7-20 Dashpot (Pneumatic) Timers Prof. Paul Lin 20 10
Solid-State Timing Relays Figure 7-21 Solid-state timing relay connections Prof. Paul Lin 21 Solid-State Timing Relays Timing Functions On-Delay Timer Figure 7-22 On-delay timer contacts Off-Delay Timer One-Shot Timer Recycle Timer Prof. Paul Lin 22 11
Timing Functions On delay timer Figure 7-23 On-delay timer circuit Prof. Paul Lin 23 Timing Functions - Off-Delay Timer Figure 7-24 Off-delay timer Prof. Paul Lin 24 12
Timing Functions Off Delay Timer Figure 7-25 Off-delay timer automatic pumping circuit Water level rises to point A => Level sensor contact on => Energize Off-delay timer => Turns on the pump to initiate the pumping action Water level decreases => Level sensor contact open => Timing begin => The pump Continue to run and empty the tank for the length of the delay time Prof. Paul Lin 25 Timing Functions - One-Shot Timer Figure 7-26 One-shot timer Prof. Paul Lin 26 13
Timing Functions - Recycle Timer Figure 7-27 Recycle timers Prof. Paul Lin 27 Multifunction Timer a timer that perform more than one timing function Figure 7-28 Multifunction digital timer H5CX-N, 0.001 s to 9999 h, http://industrial.omron.us/en/products/catalogue/control_compon ents/timers/digital_timers/default.html PLC Timers Most common types of PLC timer instructions On-delay timer (TON) Off-delay timer (TOF) Retentive Timer On (RTO) Prof. Paul Lin 28 14
Figure 7-29 PLC programmed on-delay timer Hardware wire Pressure Sw => I3 (input) Pilot Light => Q1 (Output) Enter Ladder diagram using keypad and LCD display PLC Program Execution Pressure SW on => energize Timing coil T1 => Initiating the time-delay period After 5 sec have passes, T1 (NO contact) closed to energize relay coil Q1 and turn on the pilot light Open Pressure SW, resets the time value to zero Prof. Paul Lin 29 Summary & Conclusion Questions? Contact Prof. Lin through: Email: lin@ipfw.edu LINE Group Discussion Forum Prof. Paul Lin 30 15