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DC ELECTRICAL CIRCUITS

DC ELECTRICAL CIRCUITS. INDUCTANCE. DC ELECTRICAL CIRCUITS.

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DC ELECTRICAL CIRCUITS

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  1. DC ELECTRICAL CIRCUITS INDUCTANCE

  2. DC ELECTRICAL CIRCUITS • When current travels down a conductor it creates a magnetic field around the conductor, this magnetic field induces an EMF onto the wire and will also induce a voltage onto other conductors running in parallel with the current carrying conductor. CURRENT FLOW

  3. DC ELECTRICAL CIRCUITS • Inductance is the ability of a device or circuit to oppose a change in current flow. • Induction is the action of inducing an EMF when there is a change in current. • The unit of measure for inductance is the henry (H) and the symbol for inductance is (L).

  4. DC ELECTRICAL CIRCUITS • Types of inductors;

  5. DC ELECTRICAL CIRCUITS • As you can see in the picture below an inductor can be nothing more than a coil of wire.

  6. DC ELECTRICAL CIRCUITS • The larger the conductor and the more coils it has creates a much larger inductive field, by wrapping the coil around iron the inductance increases greatly

  7. DC ELECTRICAL CIRCUITS • The symbols for inductors is pictured below.

  8. DC ELECTRICAL CIRCUITS • Most DC circuits reach the steady state condition within a fraction of a second after power is applied. • In the steady state condition the current has reached is calculated value per ohms law. • Because of other circuit characteristics the current does not reach steady state value instantaneously, there is a transient time in which the current builds up to its steady state value.

  9. DC ELECTRICAL CIRCUITS • During the time transient, when the current is changing from zero to its specified value, self induction occurs. • Self induction is the action of inducing an EMF into a conductor when there is a change of current in the conductor. • The transient time depends on the value of the inductance and the value of any resistance

  10. DC ELECTRICAL CIRCUITS • To determine the time constant of an inductor the formula is; T = L/R • In a circuit that consist of a .5mH inductor and a 1KΩresistor the time constant is; T = .005H/1000Ω or .000005uS • This means it will take 5uS for the current through the inductor to reach 63.2%

  11. DC ELECTRICAL CIRCUITS • If the maximum current through the circuit is 100A, the current after one time constant is; 100A x .632 = 63.2A • The current must increase another 36.8 amps before it reaches it’s maximum value. • During the second time constant the current increases by another 63.2% of the remaining 36.8A.

  12. DC ELECTRICAL CIRCUITS • The calculation for the second time constant is; 36.8A x .632 = 23.25A Adding this to the first time constant; 23.25 + 63.2 = 86.45A • After five times constants the current through the inductor is considered to be at its maximum value.

  13. DC ELECTRICAL CIRCUITS • Inductors in series; Lt = L1 + L2 + L3 + Ln • Inductors in parallel;

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