DS

1 Introduction Star-delta (wye-delta) starting continues to be used for switching on 3-phase induction motors. When this type of connection method is used, the starting current is reduced to 1/3 of the current required for direct switching. When switching from a star (wye) circuit to a delta circuit, transients can occur in the motor, which, further intensified by an unfavorable constellation of line frequency and inductor field, lead to the development of larger current peaks than is the case if the stopped motor is directly switched into a delta connection. In an unfavorable case, the following problems could occur: • Short-circuit devices could trip, • The delta contactor could become welded or be subject to high contact erosion, • The motor could be subject to extreme dynamic overloading. A preferred circuitry configuration for star-delta (wye-delta) starters is described in this Functional Example. When the main circuit is connected in a favorable manner, it is possible to reduce ...

 One of the more advanced ADC technologies is the so-called delta-sigma, or ΔΣ (using the proper Greek letter notation). In mathematics and physics, the capital Greek letter delta (Δ) represents difference or change , while the capital letter sigma (Σ) represents summation : the adding of multiple terms together. Sometimes this converter is referred to by the same Greek letters in reverse order: sigma-delta, or ΣΔ. In a ΔΣ converter, the analog input voltage signal is connected to the input of an integrator, producing a voltage rate-of-change, or slope, at the output corresponding to input magnitude. This ramping voltage is then compared against ground potential (0 volts) by a comparator. The comparator acts as a sort of 1-bit ADC, producing 1 bit of output (“high” or “low”) depending on whether the integrator output is positive or negative. The comparator’s output is then latched through a D-type flip-flop clocked at a high frequency, and fed back to another input channel on th...