Electrical4U 
The phasor diagram for a synchronous motor shows the steady-state relationship between per-phase voltage, current and internal emf. This article uses these symbols:Ef is the internal excitation, or counter-emfVt is the terminal voltageIa is armature current, defined into the motorΘ is the power-factor angle between terminal voltage and armature currentᴪ is the angle between internal … Read more
An induction machine operates as an induction generator, or asynchronous generator, when mechanical input drives it into its generating region. Its stator then delivers active electrical power while the machine still needs magnetising reactive power. Using the conventional slip definition, the generating conditions are: Slip becomes negative because rotor speed exceeds synchronous speed. The rotor … Read more
Developed by Walter R. Evans, the root locus technique plots the closed-loop poles of a feedback system as a selected real gain varies. For a loop transfer function K G(s)H(s), the roots satisfy the characteristic equation shown below.Open-loop poles and zeros determine the locus geometry. Closed-loop pole locations help estimate continuous-time stability and transient modes … Read more
This article introduces sampled signals and digital data in control systems. A discrete-time signal is defined only at sample instants. Digital data also has quantised amplitude values and an encoded representation. These terms are related but not interchangeable.Digital control can offer the following implementation benefits, depending on the hardware and design. Sampling converts a continuous-time … Read more
For a continuous-time linear time-invariant system, asymptotic stability requires every characteristic root to have strictly negative real part. Any right-half-plane root is unstable. Roots on the imaginary axis require separate multiplicity analysis and do not give asymptotic stability. In network synthesis and control, the Hurwitz Criterion and the Routh test are related algebraic ways to … Read more
A three phase induction motor develops torque as soon as its stator receives a balanced three-phase supply. Its torque slip characteristic explains why the motor can start without a separate rotor drive.At standstill, slip equals one and the motor develops positive starting torque. A starter is still needed to switch and protect the motor, and … Read more
A Silicon Controlled Rectifier (SCR) is a latching power semiconductor switch. Reliable operation requires every electrical and thermal stress to remain within the limits in its datasheet. A practical thyristor protection design considers: Overvoltage Protection The repetitive and non-repetitive peak voltages across an SCR must stay within its rated limits.Transients can originate inside the converter … Read more
When one device cannot meet a converter’s rating, designers may connect SCRs in series or parallel. A series string supports a higher blocking voltage, while parallel paths support a higher current. Device ratings cannot simply be added because manufacturing tolerances, temperature and circuit asymmetry affect how stress is shared. Each SCR must remain within its … Read more
The gate characteristic of a thyristor or SCR relates gate-to-cathode voltage to gate current. It helps a designer choose a trigger pulse that turns the thyristor on throughout its temperature range without overstressing the gate. The device data define maximum gate voltage Vg-max, maximum gate current Ig-max and average gate power Pgav. The graph also … Read more
A DC to DC converter changes power from one DC level or polarity to another. It lets a fixed voltage source supply equipment that needs a controlled output. Applications include traction systems, industrial drives and battery powered vehicles. A switched converter is traditionally called a chopper.The power switch operates repeatedly at high frequency. Inductors and … Read more