🔍 Key Concepts

• Function of by-pass (or suppression) capacitors in DC generator circuits • Relationship between rapid changes in current (commutation, brush sparking) and voltage spikes • How brush arcing and high-frequency noise can cause surges and radio-frequency (RF) interference

💭 Think About

• When current through an inductive winding changes suddenly at the commutator, what happens to the voltage across that winding? Think about L di/dt effects. • What does a capacitor do to very fast voltage changes or high-frequency components in a circuit? Does it block them, pass them, or smooth them? • Would a small capacitor placed right at the brushes have much effect on slow changes like normal load regulation, or mainly on very fast transient and RF phenomena?

✅ Before You Answer

• Verify whether inductance of the armature winding tends to create damaging voltage spikes when current is interrupted. • Consider if RF interference is more associated with quickly varying or slowly varying voltages/currents. • Check whether typical voltage regulation of a DC generator is normally handled by capacitors across brushes, or by other means such as field control and voltage regulators.