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**Reactive Energy:** In electrical systems, reactive energy is associated with the storage and release of energy in inductors and capacitors. Inductors store energy in magnetic fields, and capacitors in electric fields. Unlike resistors, which consume energy as heat, inductors and capacitors do not consume energy; they temporarily store it and then return it to the system. This back-and-forth flow of energy is known as reactive energy.

**Resonance in Electrical Circuits:** Resonance occurs in an electrical circuit when the inductive reactance (from inductors) and capacitive reactance (from capacitors) are balanced, resulting in the circuit's impedance being purely resistive (Ohmic). At the resonance frequency, energy oscillates between the inductor and the capacitor. This oscillation is a form of reactive energy exchange.

**Why Reactive Energy at Resonance?:** The reason resonance is associated with reactive energy lies in the nature of the energy exchange between the inductor and the capacitor. At resonance, the energy stored in the inductor's magnetic field is completely transferred to the capacitor and vice versa, at a specific frequency. This creates a state where the energy is not consumed (as it would be in a resistive load) but continuously oscillates between the inductor's magnetic field and the capacitor's electric field.

**Electromagnetic Fields:** More generally, resonance can occur in any system where electromagnetic fields oscillate, such as in radio antennas or even in molecular structures. In these cases, the concept of reactive energy still applies, as it involves the storage and release of energy in fields, rather than their conversion into heat or work.

In summary, resonance is associated with reactive energy because it represents a state where energy continuously oscillates between different forms (magnetic and electric fields in coils and capacitors) without being dissipated. This property is fundamental to understanding many phenomena in physics and electrical engineering.

**Capacitors in Delta Connection:** When capacitors are connected in a delta configuration to a three-phase network, each capacitor is connected across two phases. This allows for a continuous flow of current through the capacitors, even when no neutral conductor is present. In a system without a neutral conductor, as in the delta connection, no current can flow through the neutral conductor. Instead, the balancing current flows through the phases back to the transformer.

**Transformer in Star Connection:** In a transformer connected in a star configuration, the three windings are each connected to a phase and connected together at the star point. If the load does not use a neutral conductor, there is no direct path for current flow through the transformer's star point. Instead, the current flows through the outer phases.

**Negative Active Power:** Negative active power or negative active current arises when the phase of the current is inverted relative to the voltage. This can occur in certain cases through the use of capacitors, which cause a phase shift of the current in relation to the voltage.

**Transformer Behavior:** In this state, the transformer must handle not only the typical magnetic and electrical stresses but also cope with the effects of phase displacement. In a transformer, negative active power leads to a reduction of the apparent load on the secondary side. Negative active power on the secondary side of the transformer can lead to a reduced load on the primary winding. This means that less electromagnetic force acts on the primary winding, thus potentially reducing losses in the transformer.

In summary, negative active power in a transformer system can reduce the load on the primary side and thus potentially improve the efficiency of the transformer. However, this must be assessed in the context of the entire electrical system.

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