Electronics, Power Supplies and Communication Systems
Devices and rectification
Semiconductor basics carry into industrial work: a diode conducts in one direction; a thyristor (SCR) latches on once gated and turns off when current falls below holding; a transistor or IGBT switches and amplifies; an op-amp provides high-gain amplification, comparison and buffering. Rectifiers convert AC to DC - half-wave produces one pulse per cycle, full-wave and bridge produce two, so a 60 Hz supply gives 120 Hz ripple at the output. Filter capacitors smooth ripple; regulators hold output voltage against load and line changes. Linear supplies are quiet but inefficient; switch-mode supplies are efficient but generate high-frequency noise.
Power quality and communications
Harmonic distortion from VFDs and switch-mode supplies heats transformers and neutral conductors and can trip breakers; mitigation includes line reactors, filters and 12-pulse or active front ends. UPS systems are online (double conversion), line-interactive, or standby, each with different transfer times and ride-through. Communications in plants use RS-485 (differential, terminated, daisy-chained), Ethernet (star topology, shielded cable), and fibre (immune to electrical noise, long distances). Shielded twisted pair and proper single-point grounding prevent ground loops.
Traps
Assuming a bridge rectifier doubles the DC voltage (it doubles the ripple frequency, not the voltage); forgetting that a half-wave rectifier's output frequency equals the line frequency; treating an SCR as a self-turn-off device; and terminating an RS-485 network with a star instead of a daisy chain.
Worked example
A full-wave bridge rectifier fed from 60 Hz produces ripple at 120 Hz. With a filter capacitor and light load, the DC output approaches the peak of the AC input: for a 24 V RMS secondary, peak = 24 × 1.414 = 33.9 V, less two diode drops of about 0.7 V each, giving roughly 32.5 V DC - not 24 V.