Principles of Electromechanics

1. 16 Principles of Electromechanics

2. f u B q Figure 16.2 Charge moving in a constant field

3. i l 0 l N air r2 l l 0 gap l Figure 16.17(a) Magnetic circuit with air gap

4. 2 3 1 g + _ 4 5 Figure 16.17(b) Equivalent representation of magnetic circuit with an air gap

5. + v – i Fixed N = 700 f e x Movable Figure 16.38

6. Fixed structure N turns a l g 2 a a x x = 0 a a Nonmagnetic bushing material ( 1) r Movable plunger Spring Figure 16.40 A solenoid i

7. a a x A g Plunger Figure 16.41

8. NO or normally open (NO) relay “ Make, ” or single-pole, single throw, SPSTNO NC “ Break, ” or normally closed (NC) relay or single-pole, single throw, SPSTNC NC “ Break, make ” or single-pole, double throw transfer SPDT (B-M), or “ ” NO NC “ ” “ ” make-before-break Make, break, or or CT NO single-pole, double throw SPDT (M-B), NC or transfer, or continually transfer ” “ ” “ NO i I i I Basic operation of the electromechanical relay: The (small) coil current i causes the relay to close (or open) and enables . (interrupts) the larger current, I On the left: SPSTNO relay (magnetic field causes relay to close). On the right: SPSTNC relay (magnetic field causes relay to open). Figure 16.45 Circuit symbols and basic operation of relays