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Unformatted text preview: oad If there is a coil in the circuit, it stores magnetic energy while the circuit is closed.
When switched off, this magnetic energy is reduced suddenly thus producing an arc
across the two switching contacts which causes them damage. Different protective
measures are required depending on voltage type. 24 V D L 0V Fig. 16.1.1: Protective circuits for DC © Festo Didactic GmbH & Co. KG • FP 1110 251 16. Solutions C
L C R L R Fig. 16.1.2: Protective circuits for DC and AC C
≈ Ohmic resis tance of coil
Ω L Fig. 16.1.3: Protective circuit for AC current using a varistor 252 © Festo Didactic GmbH & Co. KG • FP 1110 16. Solutions Exercise 2.2 Switching of low electrical capacity
The switching reliability of a limit switch can be considerably improved by fitting a
resistor to the load. RL Load resistance (RL) RP Parallel resistance (RP) Fig. 16.1.4: Circuit for low contact rating 16.2
Solutions to exercises
from Chapter 3 Exercise 3.1 Maximum passing speed of a...
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- Spring '12