System for switching a load between two sources

• US 4,262,214 A
• Filed: 10/09/1979
• Issued: 04/14/1981
• Est. Priority Date: 10/09/1979
• Status: Expired due to Term

• Current Assignee: The Foxboro Company (Schneider Electric SE)
• Original Assignee: The Foxboro Company (Schneider Electric SE)
• Inventors: Patel, Haresh C.
• Primary Examiner(s): Hix, L. T.
• Assistant Examiner(s): Dwyer, James L.
• Application Number:
  US06/082,829
• Time in Patent Office: 553 Days
• Field of Search: 307/70, 307/51, 307/85, 307/86, 307/64, 307/65, 307/66, 307/67, 307/68, 361/92, 361/3, 361/6
• US Class Current: 307/51
• CPC Class Codes: H02J 9/061 for DC powered loads

Abstract

A system is disclosed for switching a load between two ac sources wherein no degree of synchronization therebetween is required and wherein the switching is accomplished with the use of two electro-mechanical relays each having a three pole, double throw contact arrangement. Furthermore, this load switching is accomplished without the production of any interpower currents between the two sources.

Claims

1. A switching system for bi-directional switching of a load between first and second independent, asynchronous a-c sources comprising:

first bi-state switching means;

second bi-state switching means in series with said first switching means and operable with said first switching means to connect said first source to said load when said first and second switch means are in one state;

third bi-state switching means;

fourth bi-state switching means in series with said third switching means and operable with said third switching means to connect said second source to said load when said third and fourth switching means are in one state;

fifth bi-state switching means;

a first bi-state actuator being coupled to said first, third and fifth switching means and being operable to control the state of said first, third and fifth switching means;

a second bi-state actuator being coupled to said second and fourth switching means and being operable in response to said fifth switching means to control the state of said second and fourth switching means;

sensor means responsive to first and second predetermined conditions of said first source and having an output for controlling the state of said first bi-state actuator and thereby controlling the state of said second bi-state actuator;

said predetermined conditions causing said actuators to sequentially change state;

said second actuator always completing its state change a predetermined period following the start of the state change of said first actuator when connecting either said first source or said second source to said load;

said predetermined period being of sufficient magnitude such that one of said sources is electically disconnected from said load before the other one is electrically connected to said load;

whereby during switching no interpower currents are produced.

2. System as claimed in claim 1 wherein said first predetermined condition is a voltage level of first magnitude;

said second predetermined condition is a voltage level of second magnitude;

said second magnitude being greater than said first magnitude.

3. System as claimed in claim 1 wherein said sources have the same frequency.

4. System as claimed in claim 3 wherein said predetermined period is greater than one-half cycle of the ac sources.

5. System as claimed in claim 4 wherein the frequency of the ac sources is 60 Hertz.