| 摘要 |
An AC electric supply of a load capable of selectively connecting a main AC power source through a first primary transformer winding or an auxiliary emergency source such as from a battery power supply through a static DC-AC converter through a second primary transformer winding, the load being connected to the secondary transformer winding. The process includes sensing the voltage of the main source and automatically connecting the auxiliary emergency source when low voltage is detected and reconnecting the main source and disconnecting the auxiliary source when the disappearance of the failure of the main source is detected by first causing the auxiliary source frequency to drift, comparing the frequency between the auxiliary source and the resupplied main source, and when the two frequencies are in coincidence, connecting the main source and disconnecting the auxiliary source. An electric supply device comprises a transformer, a main electric AC source connected to the primary of the transformer and an auxiliary electric source connected to a second primary winding of the transformer, a voltage detector for detecting low voltage of the main electric source, and controlled switches for selectively connecting either the auxiliary power supply or the main power supply, and a synchronization detector which detects when the frequency of the main power supply and the auxiliary power supply are in coincidence and controls the switches to switch from the auxiliary power supply to the main power supply.
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