ECET 211 Electric Machines & Controls Lecture 7 Relays. Lecture 7 Relays

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1 ECET 211 Electric Machines & Controls Lecture 7 Relays Text Book: Electric Motors and Control Systems, by Frank D. Petruzella, published by McGraw Hill, 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 1 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 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

electromagnet Two parts of Electromechanical Control Relay (Figure 7-1): Coil input (control circuit) Contacts

and starters Switching solenoids, pilot lights, audible alarm, and small motor (1/8 hp or less) Prof.

2 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

3 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

and Specifications Figure 7-6 Plug-in style

Paul Lin 7 and Specifications Figure 7-9

4 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

Figure 7-10 Typical solid-state relay Prof.

5 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

range: 5V DC up to 480V AC Current rating: < 10A, up to 40 A, 50A (heat sink required) Figure 7-13

6 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 11 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 12 6

Paul Lin 13 Switching Methods Solid State Relays Figure 7-16 SSR

7 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 13 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 14 7

Timing Relays An Introduction A time actuated control relay in which a fixed or

stopped at different time intervals Figure 7-18 Timing relays Part 3.

8 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 Part 3. Timing Relays Prof. Paul Lin 15 Motor-Driven Timers Part 3. Timing Relays Figure 7-19 Synchronous clock timer Dashpot Timer Figure 7-20 Dashpot (Pneumatic) Timers Prof. Paul Lin 16 8

9 Solid-State Timing Relays Part 3. Timing Relays Figure 7-21 Solid-state timing relay connections Prof. Paul Lin 17 Part 3. Timing Relays 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 18 9

10 Timing Functions On delay timer Figure 7-23 On-delay timer circuit Part 3. Timing Relays Prof. Paul Lin 19 Part 3. Timing Relays Timing Functions - Off-Delay Timer Figure 7-24 Off-delay timer Prof. Paul Lin 20 10

sensor contact open => Timing begin => The pump Continue to run and empty the tank for the length of the delay time Part 3.

11 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 Part 3. Timing Relays Prof. Paul Lin 21 Timing Functions - One-Shot Timer Figure 7-26 One-shot timer Part 3. Timing Relays Prof. Paul Lin 22 11

H5CX-N, 0.001 s to 9999 h, http://industrial.omron.us/en/products/catalogue/control_compon ents/timers/digital_timers/default.

12 Timing Functions - Recycle Timer Figure 7-27 Recycle timers Part 3. Timing Relays Prof. Paul Lin 23 Part 3. Timing Relays Multifunction Timer a timer that perform more than one timing function Figure 7-28 Multifunction digital timer H5CX-N, s to 9999 h, 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 24 12

Enter Ladder diagram using keypad and LCD display PLC Program Execution Pressure SW on => energize Timing coil T1 =>

pilot light Open Pressure SW, resets the time value to zero Prof. Paul Lin 25 Part 4.

13 Part 3. Timing Relays 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 25 Part 4. Latching Relays Latching Relays use a mechanical latch or permanent magnet to hold the contacts in their last energized position. Mechanical Latching Relays Figure 7-30 Two coil mechanical latching relay Figure 7-31 Operation of a twocoil latching relay circuit Prof. Paul Lin 26 13

Part 4. Latching Relays Magnetic Latching Relays Polarity sensitive Relay is latched when the applied voltage with a predetermined polarity.

14 Part 4. Latching Relays Magnetic Latching Relays Polarity sensitive Relay is latched when the applied voltage with a predetermined polarity. A permanent magnet is used to hold the relay in its latched position. A voltage polarity is reverses => unlatch the relay Figure 7-32 Single-coil magnetic latching relay Prof. Paul Lin 27 Latching Relay Application Part 4. Latching Relays For those applications that need to conserve the power, such as a battery-operated device Figure 7-33 Battery-operated latching alarm circuit Prof. Paul Lin 28 14

15 Part 4. Latching Relays Alternating Relay (Impulse Relays) It transfers the contacts with each pulse. For special applications where the optimization of load usage is required by equalizing the run time of two loads. Figure 7-34 Alternating or pulse relay Prof. Paul Lin 29 Part 4. Latching Relays Alternating Relay (Impulse Relays): Pumping Application Two identical pumps are used for the same job. One for normal running One for backup Running Methods 1) A standby unit is made available in case the first pump fail. However, a completely idle pump might deteriorate and provide no safety margin. 2) Both pumps get equal run time, alternately Prof. Paul Lin 30 15

Alternating Relay (Impulse Relays): Pumping Application Figure 7-35 Typical alternating relay circuit used with a duplex pumping system Use an Alternating Relay to ensure that both pumps get equal

16 Alternating Relay (Impulse Relays): Pumping Application Figure 7-35 Typical alternating relay circuit used with a duplex pumping system Use an Alternating Relay to ensure that both pumps get equal run time. In the off state, the Float SW is open, the Alternating relay is in the Load A position; both Loads (M1 and M2) are off. When the Float SW closes, it energizes the first load (M1) and PL1. Part 4. Latching Relays Prof. Paul Lin 31 Alternating Relay (Impulse Relays) Figure 7-36 DPDT crosswired contact version of a dual pumping application Alternate Mode Normal Level Lead and lag Flow SWs close simultaneously => Pumps A and B on (for heavy flow) Only one pump is operating most of the time; yet the system has the capacity to handle twice the load Part 4. Latching Relays Prof. Paul Lin 32 16

17 Part 5. Relay Control Logic Control Circuit Inputs and Outputs Figure 7-37 Typical inputs and outputs of a control ladder diagram Input section Output section Prof. Paul Lin 33 Boolean Algebra Also see - Digital Logic (pages ) Boolean Logic Logic AND Logic OR Logic NOT Truth Table V+ V- STOP START M Auxiliary Contact AND Operation M Coil ON = STOP (closed) AND START (ON) OR M Coil ON = STOP (closed) AND M Auxiliary Contact Closed M Coil OR Operation M Coil ON = SATRT (ON) OR M Auxiliary Contact Closed Prof. Paul Lin 34 17

18 Boolean Algebra Logic AND V+ V+ AND Operation M = A AND B A A B B M Coil V- V- Truth Table Inputs Output A B M Boolean Equation M = AB M AND Operation M = A AND B Coil A B M Standard Digital AND Gate Prof. Paul Lin 35 Boolean Algebra Logic OR Prof. Paul Lin 36 18

19 Boolean Algebra Logic NOT V+ V- A M Coil Truth Table Inputs Output A M Boolean Equation M = NOT A A M Standard Digital NOT Gate Prof. Paul Lin 37 Boolean Equation F Light Truth Table Inputs Output A B C F A B C F = (AB) + C Boolean Equation F = (AB) + C F = (A AND B) OR C Prof. Paul Lin 38 19

20 AND Logic Function Part 5. Relay Control Logic Figure 7-38 AND logic function OR Logic Function Figure 7-39 OR logic function Prof. Paul Lin 39 Part 5. Relay Control Logic Combinational Logic Functions Figure 7-40 AND/OR combinational logic Both (On/Off switch AND Limit switch) must be ON AND (Sensor contact or PB be ON) => Contactor coil ON Not Logic Function Figure 7-41 Not logic function Use to prevent accidental contact with live electrical connections. Prof. Paul Lin 40 20

21 Part 5. Relay Control Logic NAND Logic Function Figure 7-42 NAND logic function For dual-tank liquid filing operation NAND = NOT (FS-1 OFF AND FS-2 OFF) => Pump starter coil (OFF) => Pump Motor shut down NOR Logic Function Figure 7-43 NOR logic function NOR = NOT (Stop-1 OFF, Stop-2 OFF, Stop-3 OFF) Prof. Paul Lin 41 lin@ipfw.edu Summary & Conclusion Questions? Contact Prof. Lin through: Prof. Paul Lin 42 21

ECET 211 Electric Machines & Controls Lecture 7 Relays (1 of 2) Lecture 7 Relays

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