Processes and devices for providing a load with an electric AC supply without discontinuity of the AC signal

• US 4,510,401 A
• Filed: 03/28/1983
• Issued: 04/09/1985
• Est. Priority Date: 09/17/1981
• Status: Expired due to Fees

• Current Assignee: Etablissements Pierre
• Original Assignee: Etablissements-Pierre Fontaine
• Inventors: Legoult, Michel
• Primary Examiner(s): Pellinen, A. D.
• Assistant Examiner(s): Jennings, Derek
• Application Number:
  US06/479,179
• Time in Patent Office: 743 Days
• Field of Search: 307/66, 307/87, 307/129
• US Class Current: 307/66
• CPC Class Codes: H02J 3/42 with automatic parallel connection when synchronisation is achieved
• CPC Class Codes: H02J 9/062 for AC powered loads

Abstract

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.

Claims

1. A process for, in an electric power supply device delivering AC energy to a load without interruption and capable of being supplied by a main source and an auxiliary emergency source, switching the supply of the load from the main source to the auxiliary source, without discontinuity or frequency jump in the AC energy delivered to the load, when a failure (break) appears in the main source and reciprocally from the auxiliary source to the main source when said failure disappears, characterized in that it comprises the succession of the following steps:

the appearance of a failure of the main source is detected,

the load is disconnected from the main source, said load then being supplied by the auxiliary source in a way known per se,

disappearance of the failure of the main source is detected,

the frequency of the AC energy supplied by the auxiliary source is caused to drift,

said frequency of the auxiliary source and the frequency of the main source are compared,

the moment when these two frequencies come into coincidence is detected,

and, at the moment of this coincidence, the load is again connected to the main source and the supply of electric energy to the load from the auxiliary source is stopped.

2. The process according to claim 1, characterized in that, during the failure of the main source, the auxiliary source supplies to the load AC energy having a frequency equal to the nominal frequency of the main source and in that the frequency drift of the auxiliary source takes place in the direction of a reduction in frequency.

3. An electric supply device capable of delivering AC electric energy to a load without interruption, comprising

a transformer (1) having a secondary assembly connectable to the load to be supplied,

first means (13,14) for connection to a main AC electric source, these first connection means being connected to the primary assembly of the transformer,

second means (15,16) for connection to an auxiliary DC electric source, these second means being connected to power oscillator means (18,19) themselves connected to the primary assembly of the transformer,

means (22) for detecting a failure of the main source,

control means (23,24), made dependent on said detecting means, for selectively controlling the power supply of the primary assembly of the transformer either from the main source when this latter is in the operating condition, or from the auxiliary source when the main source is broken down (cut off),

and synchronizing means associated with said control means for synchronizing the switching of the supply from one source to the other so that there results therefrom no discontinuity in the AC power supply to the load, characterized in that, for switching from the supply from the auxiliary source to the supply from the main source when a failure of this latter disappears, the synchronizing means comprise:

means (21) for detecting the frequency of the main source,

means for detecting the frequency of the power oscillator means,

means (26) for controlling the frequency drift of the power oscillator means (18,19), these frequency drift controlling means being under the dependence of the means (21) for detecting the frequency of the main source,

means (27) for detecting the coincidence of the frequencies of the main source and of the power oscillator means,

and synchronous switch means (28) placed under the control of said frequency coincidence detection means, for disconnecting the main source from the primary assembly of the transformer when a failure of the main source occurs and for reconnecting the main source to the primary assembly of the transformer when said failure has disappeared and when said frequencies coincide.

4. The device according to claim 3, characterized in that the means (22) for detecting a failure of the main source are voltage detection means, in that the means (21) for detecting the frequency of the main source and the means (22) for detecting the voltage of the main source are disposed in this order between the main source and the primary assembly of the transformer, and in that the synchronous switch means (28) are disposed between the means for detecting the frequency and the means for detecting the voltage of the main source.

5. The device according to claim 3, wherein the power oscillator means comprise an oscillator (19) and a power inverter (18), characterized in that the frequency drift controlling means are connected to the oscillator.

6. The device according to claim 3, wherein the power oscillator means comprise an oscillator (19) and a power inverter (18), characterized in that between the oscillator and the power inverter is disposed a disabling member (23) placed under the control of the means for detecting the voltage of the main source, so that, when said main source operates normally, the disabling means disconnect the oscillator and the power inverter whereas, should a failure of the main source occur, the disabling means connect the power inverter to the oscillator.

7. The device according to claim 3, characterized in that the frequency of the auxiliary source is equal to the nominal frequency of the main source and in that the frequency drift controlling means are adapted to cause a reduction of the frequency of the auxiliary source.

8. The device according to claim 3, characterized in that the primary assembly of the transformer 30 (1) comprises a first primary winding (2) connected to said first connection means and a second primary winding (3) connected to said second connection means.

9. The device according to claim 3, characterized in that the transformer is a ferro-resonant transformer.

10. The device according to claim 8 characterized in that said transformer further includes a magnetic shunt for isolating said first and second primary windings from said transformer secondary assembly, and characterized in that said first and second primary windings are located on the same one side of said shunt.

11. The device according to claim 10 characterized in that said transformer secondary assembly comprises a secondary winding located on the other side of said shunt.