Source circuit

The transformer has an inductance and is often represented in a transient calculation by its leakage inductance L [H], which is evaluated by its capacity P [W], the rated voltage V [V], and the percent impedance (%Z) as 

A single-phase line with an inductive source e t)=E cos((at). 

Included in the figure (--) is the case of no source inductance, which is 

In such a time period, the ac voltage in Equation 2.4 can be regarded as a step voltage with the amplitude E. 

When a much longer time period of calculations is required, a source should be represented as a sinusoidal ac source. In the case of fault clearing and load rejection overvoltages, the observation time exceeds 1 s, and the mechanical and electrical characteristic of a generator is to be considered including generator control. In such a case, the sinusoidal ac source is not appropriate, and Park s generator model is often used. 

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FIGURE 3.1 Power system consisting of source, circuit breaker, transformer, and load. 

Driving circuits for micro-heaters this generally requires a stable, accurate current or voltage source circuit with large current (tens of milli-amps) driving capability. 

An interesting feature of the Z-source DC circuit breaker is its ability to automatically respond to a short-circuit fault in its DC load and to protect the power source from the fault. A Z-source circuit breaker between a power source and an inverter (Fig. 8.47) allows to simultaneously close the upper and the lower power switch of an inverter phase leg. The combination of a Z-source circuit and an inverter is known as Z-source inverter (ZSI). If both switches of a phase leg are on, the inverter is said to be in shoot-through mode. That is, the Z-source inverter has another mode in addition to the six active modes and the two null modes of a traditional 3-phase inverter. 

When a number of generators, transformers, and/or transmission lines are connected to the bus in Figure 2.4, the source impedance = jcoL becomes very small. Such a bus is called an infinite bus, and the source circuit becomes equivalent to the ideal source in Figure 2.2. A switching overvoltage generated in the infinite bus case is the severest, as observed from Figure 2.3. 

The surge impedance matrix [Z ] of the source circuit and [Z ] at the right of node r are... 

The input (gate-source) circuit of a MOSFET can be simply illustrated by a capacitor Qsj. The output (drain-source) circuit is expressed by an equivalent resistor R seq a capacitor C ss- The resistance of the equivalent resistor R seq is controlled by the gate-source voltage. 

Figure 6.3 shows surge voltages at various parts of control circuits (1) VT secondary (2) CT secondary (3) source circuit DC 110 V P-E and (4) CB control (pallet) circuit. In general, the figure depicts the following trend of the voltage amplitude ... 

CT secondary > VT secondary > source circuit > CB control circuit. 

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