1 AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION STANDARD PATENT "Electric Motor Controller" The following statement is a full description of this invention, including the best method of performing it known to me: 2 ELECTRIC MOTOR CONTROLLER 5 Field of the Invention This invention relates to an electric motor controller. It relates particularly but not exclusively to a controller which can be used to control electric pump motors used in irrigation systems. 10 Background of the Invention In many large motor installations, such as those involved in agricultural irrigation, the electric pump motor is started with what is known as a "star delta" starter. This 15 device is intended to reduce the load on the power grid while the motor is spinning up to speed. Once the motor is running at full speed (after about 3 seconds) the controller switches from star mode to delta mode. This switching function is often controlled electromechanically using a series of electric "contactors". In order to function properly these contactors rely on the power supply to magnetically "hold in" 20 the switch circuit such that when the power fails (or the stop button is pressed) the electromagnetic field collapses and the switch drops out. This makes the pump stop and of course, when the power is restored the pump will not start again until the start button is pressed. This is a major problem in the irrigation environment (amongst others) where the farmer may have to get out of bed, climb on his motorbike and 25 restart the pump at the pumpshed - very annoying especially when the power might only be out for a few seconds. To restore the power to the pump the user is required to press the start button again in order to reenergise the electromagnet and restart the motor. 30 Large motors of this sort cannot be overly "cycled" (turned on and off) without allowing them to come and remain briefly at a complete stop, thus letting the overload circuit cool down. Cycling the motor too rapidly or too many times in a 3 short space of time is severely detrimental to the motor, motor starter and the system to which it is connected. The invention seeks to provide a controller which may be used to address one or more 5 of the disadvantages associated with motor installations of the type described above. Disclosure of the Invention The invention provides in one aspect a controller for controlling electrical power from 10 a power supply to a motor, comprising a microprocessor set to restore supply of the electrical power to the motor after an interruption of the electrical power and to stop the supply of electrical power to the motor if the number of interruptions exceeds a predetermined number. 15 In effect the controller may provide power in parallel with an existing start button, providing mains power to a starter contactor, which in turn controls power to the electric motor. This arrangement provides a logical 'or' such that the motor can be started either by pressing the existing start button or can be started by the invention herein described. 20 The motor may comprise a pump motor. The pump motor may be set for pumping water in an agricultural irrigation installation. There may be more than one motor in the installation. The controller may be used to control a plurality of motors in the installation or more suitably there may be a controller for each motor. 25 Where there is more than one motor in an installation each motor may be fitted with a separate controller, each controller may have a certain 'random' timeout in addition to its anti cycling timer such that when the power supply is restored not all motors in the installation try to restart at the same instant. 30 The microprocessor may be set to restore power after a predetermined time span. The predetermined time span may typically be between 5 seconds and 3600 seconds. More specifically it may be between 60 seconds and 600 seconds.
4 The predetermined number of interruptions may be between 2 and 50 interruptions. More specifically, it may be between 3 and 10 interruptions. It is useful to limit the predetermined number of restarts from interruptions as excessive restarts can wear 5 out the pump. The counting of the number of interruptions may be arranged so that the supply of electrical power to the motor is not restored by the microprocessor if a predetermined number of interruptions occurs within a specific time span. 10 If the number of interruptions within the specific time span does not exceed the predetermined number, the microprocessor may reset the count of interruptions to zero after a predetermined period of stable power supply. 15 The microcontroller may comprise an electrically erasable programmable memory. It may comprise a non-volatile electrically erasable programmable read-only memory (ceprom). The microprocessor may be set so as to delay restoration of the supply of the 20 electrical power after a specific duration of time. It may also activate a warning during the period of delayed restoration of power supply. The warning may be an audible warning. It may be provided by piezo buzzer. Preferred aspects of the invention will be described with reference to the 25 accompanying drawings. Brief Description of the Drawings Figure 1 shows a schematic block diagram of some of the hardware components 30 arranged for operation of the invention; Figure 2 shows a logic diagram for operation of an embodiment of the invention; and Figure 3 shows a circuit diagram of a controller and 'star' delta starter.
5 Detailed Description of the Preferred Embodiment The various elements identified by numerals in the drawings are listed in the 5 following integer list. Integer List 1 Mains power supply 10 10 Starter box 11 Start button 12 Stop button 13 Start delta starter 14 Indicator LED is 20 Mains sensor 21 Auxiliary sensor 22 Low voltage power supply 23 Microcontroller 25 Eeprom 20 28 Piezo buzzer 29 Control Relay 30 Motor Logic Steps 25 35 Mains contactor setting 36 Eeprom setting 37 Auxiliary contactor setting 39 Eeprom fail code signal 30 42 Auxiliary contactor setting 43 Auxiliary contactor setting 44 Set delay 45 Mains contactor monitor 6 46 Eeprom fail code clearance 48 Period of off power 50 Count restarts 51 Alarm activation 5 53 Motor restart 54 Eeprom reset 56 Restart lockout Referring to Figures 1 and 3 of the drawings, a typical controller arrangement 10 according to the invention controls power from a mains power supply I. A starter box 10 having a start button 11 and a stop button 12 associated a typical star delta starter 13 is arranged for setting power to the motor 30. 15 The controller controls power to pump 30 via the starter box and has as its "heart" a microcontroller 23. The microcontroller is powered by a low voltage power supply 22. The microcontroller comprises an eeprom 25 and is arranged to direct warning signals 20 to a piezo buzzer 28 and indicator LED. The microcontroller is configured to send signals to the power relay 29 so as to restore mains power supply to the motor 30 after a power stoppage when the power is restored. This is in response to the status of the mains sensor 20 and the auxiliary 25 sensor 21. The mains sensor 20 will be closed when power is present and the auxiliary sensor is closed when the motor is running. The mains contactor opens when power is not present. Similarly, the auxiliary contactor opens when the motor has stopped 30 running. The mains sensors and auxiliary sensors are electrical contactors which are either in a closed or open state. Their state is registered by a microcontroller.
7 Referring to Figure 2, there is shown a typical sequence of logic steps for controlling a motor for an irrigation pump using the controller set up described in relation to Figure 1. 5 The controller is interfaced with the starter box 10 for an irrigation installation. When mains power supply I is present, prior to pressing the start button the mains relay is closed in step 35 and the control relay 29 is open. Because the system has not been started the ceprom does not register a fail code in step 36. 10 Furthermore because the motor has not been started the auxiliary contactor 21 is registered as being open in subsequent step 37 by the microprocessor. Thus the system is in standby mode and the logic loop of steps 36 and 37 continues to operate for so long as mains supply power is present and the start button 11 has not been pressed on. 15 However when the pump is to be started by pressing the start button 11 the auxiliary contactor registers as being closed and a fail code is written to the ceprom in step 39. The microprocessor continues to periodically monitor the auxiliary motor contactor 20 21 in step 42. If the auxiliary motor contactor is still closed at step 43, it reverts to periodically monitoring the status of the auxiliary motor contactor via step 42 until such time as the motor has stopped. 25 If the motor stops the microprocessor moves to step 44 to wait a prescribed period of time after the motor has stopped. This is a very short wait, usually of the order of tens of milliseconds, to compensate for relay bounce. The microprocessor then moves to step 45. 30 If the mains contactor 20 is closed indicating the presence of mains supply in step 45, the motor will have been shut down normally by pressing the stop button 12 and the microprocessor will clear the fail code from the eeprom in step 46. It then continues 8 to monitor the status of the auxiliary motor contactor as per the loop between steps 37 and 36 until such time as the motor is restarted by pressing the start button 11. In the event that the auxiliary contactor 21 opens because the mains supply fails the 5 microprocessor registers that the mains contactor 20 is open in step 45. The microprocessor then goes to step 48 where it suspends all action for a predetermined period, typically between 60 and 600 seconds, to allow the motor sufficient time to stop and cool down before any restarting action is initiated. 10 After the predetermined period, the microprocessor senses the state of the mains relay in step 48. If power is present the microprocessor registers the mains relay being closed in logic step 35. In step 36 the microprocessor then registers the presence of a fail code in the eeprom 15 and moves to step 50 where it interrogates the eeprom as to the number of restarts which have been performed. Following the previous description this should be 0 restarts although as will be described hereinafter the eeprom will incrementally register restarts up to a predetermined maximum which will usually be at least 1 or more restarts. 20 However in this case as the eeprom only registers 0 restarts in step 50 the restart maximum has not been reached. The microprocessor therefor moves to step 51 during which it activates the audible warning 28 and waits a predetermined time before it restarts the motor by closing the control relay 29 in step 53. The control 25 relay 29 duplicates the function of the start button 11. In closing the control relay 29 the microprocessor also incrementally registers a restart in the eeprom in step 55. The microprocessor returns to step 37 and proceeds through the loop spanning steps 37, 39, 42, 43, 44, 45 and 46 until power is interrupted again or the stop button 12 is 30 pressed. In the event that power is interrupted a number of times the microprocessor goes through the logic loop starting at step 45 through 35, 36, 50 etc until the maximum 9 restarts limit has been reached at which time the microprocessor in step 56 locks out the restart and powers the LED indicator 14. The system is then in standby mode until such time as it is manually restarted by an operator. 5 However, if the power is interrupted less than a predetermined number of times within a predetermined time span the microprocessor may reset the number of restarts registered by the eeprom to zero. In general terms the controller system quietly monitors the status of the pump and the to power supply. When the pump is started an error message is written directly to the eeprom. Should the power fail at any time prior to the pump being stopped appropriately, no power will remain to clear this error message. Consequently, once power is restored the error message will still be present and the restart can be performed. Should the pump be stopped appropriately (while the mains power supply 15 remains present) then the system can clear the error message and await the next cycle. When the system detects the need to perform a restart it will first delay further action for a specified duration. This ensures that the pump is not cycled too quickly and ensures the power supply is indeed stable prior to starting up. During this delay the 20 system will beep repeatedly to inform anyone in the vicinity that the pump is about to be restarted automatically and should therefore not be touched. The system also counts the number of restarts it performs and will lock out the system once a predetermined value has been reached. Once the pump has been restarted and has run successfully for a given period (eg. 1 hour) or the pump has been manually started or 25 stopped then the restart count is zeroed ready for future action. At anytime after an automatic restart and before the expiration of the settling period a bright red indicator light may flash so that the user is informed, should they visit the pump shed, that there has been a power failure and that the pump has been restarted by the system. 30 Whilst the above description includes the preferred embodiments of the invention, it is to be understood that many variations, alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously 10 described without departing from the essential features or the spirit or ambit of the invention. It will be also understood that where the word "comprise", and variations such as 5 "comprises" and "comprising", are used in this specification, unless the context requires otherwise such use is intended to imply the inclusion of a stated feature or features but is not to be taken as excluding the presence of other feature or features. The reference to any prior art in this specification is not, and should not be taken as, 10 an acknowledgment or any form of suggestion that such prior art forms part of the common general knowledge in Australia.