3/4/2015. Basic relay construction. Shading coil in AC relays. Timothy L. Skvarenina and William E. DeWitt Electrical Power and Controls, 2e

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Lucas Miller
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1 FIGURE 12-1 Basic relay construction. FIGURE 12-2 Shading coil in AC relays. 1

2 FIGURE 12-3 Contactor coil and shaded pole stators. FIGURE 12-4 Magnetic motor starter. 2

3 FIGURE 12-5 Thermal overload devices. FIGURE 12-6 Motor starters with electronic overloads. 3

4 FIGURE 12-7 Time-delay relay contact symbols. FIGURE 12-8 Pneumatically controlled time-delay relay. 4

5 FIGURE 12-9 Schematic symbols for push buttons. FIGURE Start/stop push-button station. 5

6 FIGURE Push-button control of two pilot lights. 6

7 FIGURE Control station. FIGURE Schematic symbols for pressure, float, flow, temperature, and limit switches. 7

FIGURE 12-14 Limit switch. MEMA Enclosure Types (page 563) NEMA Enclosure Types, https://www.nema.org/products/documents/nemaenclosure-types.

8 FIGURE Limit switch. MEMA Enclosure Types (page 563) NEMA Enclosure Types, NEMA Enclosures, EATON, l/selectcountry/index.htm?wtredirect= electrical 8

9 FIGURE Schematic symbols for several devices. FIGURE Motor starter wiring diagram. 9

10 FIGURE Motor starter schematic diagram. FIGURE Two-wire and three-wire control methods. 10

11 FIGURE A ladder diagram. FIGURE Logic circuits. 11

12 FIGURE State diagram for the control system of Figure Example 12-1 Example 12-1 Design controls for a three-phase AC heater/blower system that meets the following specifications: 1. Circuits should have manual on/off control. 2. The blower should not come on until the heater is warm. 3. A green light should be on whenever the start switch is on and the heater is off. 4. A read light should be on when the heater is on. 5. Heater and blower turn off when the desired temperature is reached 6. Once start is pressed, the system cycles on and off as temperature changes. 12

FIGURE 12-22 Power circuit for the system of Example 12-1.

13 FIGURE Power circuit for the system of Example FIGURE State diagram for heater/blower system of Example

14 FIGURE Ladder diagram for heater/blower of Example Reduced-Voltage AC Motor Starters Reduce line voltage => reduce line current Need to keep starting current low, but maintaining enough starting torque) Methods Auto transformer starting Y-Delta staring Electronic soft starting FIGURE motor. Autotransformer starting of an induction 14

15 Reduced-Voltage AC Motor Starters FIGURE motor. Autotransformer starting of an induction FIGURE Closed-transition autotransformer starting. 15

16 FIGURE Wye-delta starting. FIGURE Soft starter and electronic motor starter. 16

FIGURE 12-29 Electronic soft-starter concept.

17 FIGURE Electronic soft-starter concept. FIGURE Motor characteristics with hard start. 17

18 FIGURE Motor characteristics with soft start. Reversible Starters T1 T2 T3 Forward Operation Phase A-T1, B-T2, C-T3 Reverse Operation Phase A-T1, B-T3, C-T2 FIGURE Reversible starter with mechanical interlocking. 18

19 FIGURE Reversible starter with electrical interlocking. FIGURE Equivalent circuit of a DC shunt motor. 19

20 FIGURE Three-point manual DC motor starter. FIGURE Four-point manual DC motor starter. 20

21 FIGURE DC motor with starting resistors in armature circuit. FIGURE Definite-time DC motor starter. 21

22 FIGURE Counter EMF DC motor starter. FIGURE Current-limit DC motor starter. 22

23 FIGURE a. Safety relay. b. Gate interlock relay. FIGURE Basic application example. 23

24 FIGURE Application example with redundancy. FIGURE Application example with a safety relay. 24

25 FIGURE Application example with redundancy, diversity, and monitoring. FIGURE Figure for Problems 12-8, 12-9, and

26 FIGURE Figure for Problem

ECET 211 Electrical Machines and Controls

ECET 211 Electrical Machines and Controls 2016/4/27 Class Review and Wrapping Up Comprehensive Exam, Friday, 1:00-3:00 PM, May 6, 2016 Close books/allow 1-page (8 x 11 and ½) hand-written review note,