Final answer:
DC voltage in a three-phase alternator is typically provided through electronic methods using rectifiers and filters, although it can also be mechanically generated with multiple coils and split rings.
Step-by-step explanation:
To provide DC voltage in a three-phase alternator, a mechanical arrangement or an electronic method can be employed. Mechanical methods include the use of multiple coils and split rings to produce pulsed DC, which can be smoothed out to reduce ripple. However, in modern applications, electronic means are often preferred to achieve ripple-free DC. These electronic methods typically involve rectifiers, which convert AC to DC, and filters to smooth out the resulting DC voltage. Additionally, most alternators initially produce AC voltage due to the rotation of wire loops in a magnetic field, which is then converted into DC using the described methods.