Abstract:
An electrical power controller controls the selection of power sources, backup generator and normal utility line, to an automatically controlled load and other loads during and at the end of a power failure in a system. As long as the automatic load needs to be on, the power controller will connect the automatic load directly to a backup generator bypassing the transfer switch and disable a stop generator signal. When utility power returns, the transfer switch switches all other loads to operate from utility power and the transfer switch sends the stop signal to the backup generator. However, only when the power controller determines that the automatic load is no longer turned on will it re-enable the stop signal and return the automatic load to normal utility power selected by the transfer switch.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electrical power controller, which is added to a system having a backup generator and transfer switch, to control the backup power of an automatic load while backup power to other loads in the system are controlled by the transfer switch. The electrical power controller also controls the application of power to the automatic load during an exercising of the backup generator. 
     2. Description of the Related Art 
     In the related art, devices to control the turn on and off of the backup generator or other backup power source and provide the transfer of the connection of loads from the utility power to the backup power source when a power failure of the utility power occurs have been handled by one device with limited functions. Devices of this type are shown in U.S. Pat. No. 6,172,432 to Schnackenberg et al issued Jan. 9, 2001; U.S. Pat. No. 6,181,028 to Kern et al issued Jan. 30, 2001 and European Patent EP0328706 issued Aug. 8, 1989. Schnackenber et al discloses a load shedding feature for removing and restore different circuits. The other related art devices listed above do not provide other features. 
     In another related patent, U.S. Pat. No. 4,016,458 to Everhart issued Apr. 5, 1977, shows a device in which essential ones of the distribution amplifiers can be maintained operative by a DC standby power during AC line power hiatus and less important amplifiers are automatically rendered inoperative during power faults to prevent excessive drain on the standby source. 
     None of the prior art devices above provide control of power source supply to loads when the power utility failure ends. 
     It would be desirable to have a device to maintain the operation of an automatic load on the backup power source even after the return of normal utility power source and after the automatic load decides to stop, so as to prevent harmful surges or spikes that would occur if the automatic load is switched from a backup source to a utility power source during a required need for the automatic load to be turned on. 
     It would also be desirable to have a device that can at prescribed times exercise or test the operation of the backup power source only when the automatic load decides that it needs to run. 
     None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus an electrical power controller solving the aforementioned problems is desired. 
     SUMMARY OF THE INVENTION 
     The present invention is an electrical power controller to control the application of power to an automatically controlled load and other loads during and at the end of a power failure in a system. 
     The electrical power controller can be used in a plant such as a manufacturing plant or sewage treatment plant, which has a backup generator powered by some fossil fuel and a transfer switch as well as normal utility power The transfer switch normally controls the start up of a backup generator upon sensing a utility power failure and transfers the connection of all the loads from the utility power to the backup generator. When utility power returns, the transfer switch normally transfers the connection of all the loads from backup generator power to the utility power and controls the shutdown of the generator. The loads in the system may or may not be automatically controlled loads. 
     In a manufacturing plant or sewage treatment plant, an automatically controlled load is one like pumps that have sensors and relays to turn them on only when a water level in a well reaches a certain level and turns them off when the water level in the well that it has pumped reaches a lower level. Another example would be a furnace which is controlled to turn on and off by temperature. Such loads benefit from fewer surges and spikes on their power line input, if their sources of supply are not switched while running. 
     Thus, the instant invention adds a controller, such as programmable logic controller, having inputs and outputs; relays and lamp indicators to the above system. 
     The controller operates with inputs from the normal utility power source and the automatic load sensors in the automatically controlled load to prevent the connection transfer of automatic loads back to utility power even if the utility power failure has ended and as long as the automatic load sensors still require the automatic load to continue to operate. This is done by disabling the shut down of the backup generator and bypassing the transfer switch to provide the backup generator power directly to the automatic load power input. In the meantime the transfer switch, which has been prevented from shutting down the generator, will transfer other loads back to the utility power at the end of the utility power failure. Once the sensors stop calling for operation of the automatic load will the controller allow the automatic load to run on utility power by reconnecting the automatic load power input back to the transfer switch and release control of the generator back to the transfer switch for shutdown of the generator. At this point the automatic load sensors will have the automatic load turned off, and the automatic load is later ready to use the utility power. 
     The power controller also uses the same relays and monitors the same inputs to exercise or test the operation of the backup power source at prescribed times when there is no utility power failure and only when the automatic load decides that it needs to run. 
     Accordingly, it is a principal object of the invention to provide an electrical power controller that keeps an automatic load running on backup generator power even after utility power is restored by controlling the stop and start signal of the generator and controlling bypass relays. 
     It is another object of the invention to provide an electrical power controller that prevents an automatically controlled load from experiencing damaging power surges or spikes. 
     It is a further object of the invention to provide an electrical power controller that treats an automatically controlled load differently from other loads in system during and after a power failure of normal utility power. 
     Still another object of the invention is to provide an electrical power controller, that functions at prescribed times during normal operation of the utility power to exercise or test the operation of the backup power source only when the automatic load decides that it needs to run. 
     It is an object of the invention to provide improved elements and arrangements thereof for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes. 
     These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an electrical diagram of the electrical controller according to the present invention. 
     FIG. 2 is a flow diagram of a first operational feature of the present invention. 
     FIG. 3 is a flow diagram of a second operational feature of the present invention. 
    
    
     Similar reference characters denote corresponding features consistently throughout the attached drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention as shown in FIG. 1 includes a power controller  10 , which is connected to an output from the normal utility power source  22 . The power controller  10  senses and uses the output from the utility power source  22 . Since the power controller  10  senses the loss of power from the normal utility power source  22  and is expected to function during the power failure, it should have its own source of backup power source provided by batteries connected internally to the power controller  10 , which are recharged by the utility power source  22 . Another input of the power controller  10  is connected to automatic load sensors  28 , so that it can determine when the automatic load  12  is requested or required to turn on. The power controller  10  can be a programmable logic controller or microcomputer as is well known in the art. 
     The automatically controlled load  12  is one like pumps that have sensors  28  and relays to turn them on only when a water level in a well reaches a certain level and turns them off when the water level in the well that it has pumped reaches a lower level. Another example would be a furnace which is controlled to turn on and off by temperature. Such loads benefit from fewer surges and spikes on their power line input, if they are not switched while running. 
     A control output of the power controller  10  is connected to control a relay  14 , so that it can bypass power output by the transfer switch  20  and receive power output by the backup generator  24  directly. Another control output of the power controller  10  is connected to a relay  29  to disable or enable the stop or start signal output from the transfer switch  20 , which is input to a control input of the generator  24 . 
     The transfer switch  20  is connected to the output of the normal utility power source  22  to sense its loss during a power failure and transfer its connection to and from the other loads  26  and automatic load  12 . The transfer switch  20  is connected to the output of the backup generator source  24  for transferring its connection to and from the other loads  26  and automatic load  12 . 
     The transfer switch  20  also uses the output of the backup generator  24  to see if it is up to speed and is providing the correct voltage after an initial startup. The transfer switch  20  has a stop and start signal output, which is also connected to a control input of the backup generator source  24  for controlling the stop and start of the generator  24 . 
     The power controller  10  controls the relay  14 . Under control of power controller  10 , the relay  14  selects a power source connection of the automatic load  12  to either the output of the backup generator  24  directly or the output of the transfer switch  20 . As shown relay  14  uses a double throw, double pole switch. The relay  14  may use a triple or quadruple pole switch in case the other loads  26  and automatic load  12  use 3 or 4 phase power sources, in which case the number of lines connecting the power sources and loads shown in FIG. 1 would also be more numerous. 
     The power controller  10  controls the relay  29 . Under control of the power controller  10 , the relay  29  enables or disables the stop signal output from the transfer switch  20 , which is sent to the backup generator  24 , by opening or closing of the connection. On the other side of the switch on the relay  29  closest to the backup generator  24 , a pull-up or pull-down resistor maybe used to provide a proper voltage level of the stop signal when the switch is open. 
     Light indicators  16  and  18  are connected to outputs of the power controller  10  to indicate to the system the status of generator  24  exercise tests and automatic load  12  function. 
     Normally, the transfer switch  20  monitors the voltage output from the utility power  22  while it supplies the utility power  22  to other loads  26  and automatic load  12 . Upon sensing a significant loss of voltage output from the utility power  22 , the transfer switch  20  outputs a start signal to the generator  24  and waits for generator  24  to come up to speed with an acceptable voltage. Once the acceptable voltage is reached, the transfer switch  20  switches to supply power from the generator  24  to the loads  12  and  26 . 
     As shown in the flow diagram of FIG. 2, power controller  10  provides the function of sensing the utility power failure at step  32 . If the power controller  10  senses a utility power failure, then at step  34  it activates the relay  14  so that the automatic load  12  receives power from the backup generator  24  after a short delay time to ensure that the generator  24  has had time to completely startup. Alternately, the power controller  10  may have an input connected to the backup generator  24  to sense when the generator  24  has come up to speed with an acceptable voltage as does the transfer switch  20 . 
     At step  34 , the power controller  10  also outputs a control signal to relay  29  to disable any stop signal output from the transfer switch  20 . The automatic load  12  may be turned on or off at any time during the power failure as controlled by the sensors  28 . The crucial time is when the power failure ends. So in step  36 , the power controller  10  continuously checks to see if the utility power source  22  has resumed operation. Only if the utility power source  22  has resumed operation does the power controller  10  move to step  38 . 
     At step  38 , the power controller  10  checks sensor  28  to see if the automatic load  12  is running and turned on. If the automatic load  12  has been turned on then the controller  10  continues to check for the running automatic load  12  and continues the disabling of the stop signal output from the transfer switch  20  and continues the control of relay  14  to keep the power of automatic load  12  connected to the still running backup generator  24 . When the automatic load  12  has been turned off the power controller  10  can move to step  40 . At step  40 , the power controller  10  will cut off the output to relay  14  causing the safe return of power to be provided to the automatic load  12  from the transfer switch  20 , which is now providing power from the utility power source  22 . Also at step  40 , the power controller  10  will enable the stop signal output from the transfer switch  20 , so that the generator  24  will be shutdown. 
     Therefore, harmful surges or spikes that would occur if the automatic load  12  was switched from one power source to another during a required need for the automatic load to be turned on is prevented. 
     As shown in the flow diagram of FIG. 3, power controller  10  provides the further function of exercising or testing the operation of the backup power source  24  at prescribed times during normal operation of the utility power and only when the automatic load  12  decides that it needs to run. 
     At prescribed times provided by a clock or timer within the power controller  10  a exercising of the function of the backup generator  24  is called for. When an exercise time has occurred as in step  52 , the automatic load  12  is checked to see if it has been turned on by sensors  28  in the automatic load  12  as shown in step  54 . As shown in step  54 , the power controller  10  continues to wait for the automatic load  12  to be turned on. If the automatic load  12  has been turned then it is ok to start the generator  24  via relay  29  and connect the automatic load  12  to the generator  24  via relay  14  as shown in step  56 . Then in step  58 , the power controller  10  checks the sensors  28  of the automatic load  12  to see if the sensors  28  are still on. If the automatic load  12  is still on due to sensors  28 , then the controller  10  allows automatic load  12  to continue to be using the power from the running backup generator  24 . If the automatic load  12  is no longer turned on due to sensors  28 , then it is safe disable the backup generator  24  via relay  29  and return the connection of power for automatic load  12  to the utility power  20  via relay  14  as shown in step  60 . 
     Therefore, harmful surges or spikes that would occur if the automatic load  12  was switched from one power source to another during a required need for the automatic load to be turned on is prevented. 
     It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.