System and method for sleep mode for a pumping system

Abstract

A method of controlling a motor in a liquid system is provided, comprising: controlling an operating frequency of the motor to cause a pump to maintain an actual pressure of liquid in the liquid system at or near a first pressure; determining whether a first timer has elapsed during the controlling step; responding to a determination that the first timer has elapsed by initiating a sleep mode determination, comprising: ramping the operating frequency to a low frequency; determining whether the actual pressure remains above a second pressure which is less than the first pressure for a second timer; and responding to the actual pressure remaining above the second pressure for the second timer by causing the motor to enter a sleep mode.

What is claimed is: 
     
         1 . A method of controlling a motor in a liquid system, comprising:
 controlling an operating frequency of the motor to cause a pump to maintain an actual pressure of liquid in the liquid system at or near a first pressure;   determining whether a first timer has elapsed during the controlling step;   responding to a determination that the first timer has elapsed by initiating a sleep mode determination, comprising:
 ramping the operating frequency to one of a low frequency or a high frequency;
 determining whether the actual pressure remains, for a duration of a second timer, one of above a second pressure which is less than the first pressure after ramping the operating frequency to the low frequency or below a third pressure which is greater than the first pressure after ramping the operating frequency to the high frequency; and 
 
 responding to the actual pressure remaining, for the duration of the second timer, one of above the second pressure or below the third pressure by causing the motor to enter a sleep mode. 
   
     
     
         2 . The method of  claim 1 , wherein the low frequency is a PID Lo Limit. 
     
     
         3 . The method of  claim 1 , wherein the high frequency is a PID Hi Limit. 
     
     
         4 . The method of  claim 1 , further comprising:
 determining whether, while the motor is in the sleep mode, the actual pressure one of drops below a fourth pressure which is less than the second pressure or increases above a fifth pressure which is greater than the third pressure; and   responding to the actual pressure one of dropping below the fourth pressure or increasing above the fifth pressure by causing the motor to exit the sleep mode.   
     
     
         5 . The method of  claim 4 , wherein determining whether the actual pressure drops below the third pressure includes computing a pressure error between the actual pressure and the fourth pressure and determining whether the pressure error is greater than zero. 
     
     
         6 . The method of  claim 1 , wherein determining whether the actual pressure remains above the second pressure includes computing a pressure error between the actual pressure and the second pressure and determining whether the pressure error is greater than zero. 
     
     
         7 . The method of  claim 1 , wherein the sleep mode determination further comprises responding to the actual pressure, during the second timer, one of dropping below the second pressure or increasing above the third pressure by exiting the sleep mode determination and returning to the controlling step. 
     
     
         8 . The method of  claim 1 , wherein controlling the operating frequency of the motor includes controlling a variable frequency drive to vary power provided to the motor. 
     
     
         9 . The method of  claim 1 , wherein the duration of the second timer is based upon the operating frequency of the motor when the first timer has elapsed. 
     
     
         10 . The method of  claim 9 , wherein a range of the operating frequency extends from the low frequency to the high frequency, the range being divided into a plurality of zones, and the duration of the second timer is based upon which of the plurality zones the operating frequency of the motor falls when the first timer has elapsed. 
     
     
         11 . A system for controlling an actual pressure of liquid in a liquid system, comprising:
 a motor drive including a controller and an inverter connected to the controller;   a motor driven connected to the inverter;   a pump connected to the motor, the pump being configured to deliver liquid to at least one conduit of the liquid system; and   a pressure sensor configured to provide the controller measurements of an actual pressure of liquid in the at least one conduit;   wherein the controller is configured to control an operating frequency of the motor in response to the actual pressure from the pressure sensor to cause the pump to maintain the actual pressure at or near a first pressure; and   wherein the controller is further configured to respond to a first timer elapsing by initiating a sleep mode determination, comprising:
 ramping the operating frequency to a low frequency;
 determining whether the actual pressure remains above a second pressure which is less than the first pressure for a duration of a second timer; and 
 
 responding to the actual pressure remaining above the second pressure for the duration of the second timer by causing the motor to enter a sleep mode. 
   
     
     
         12 . The system of  claim 11 , wherein the low frequency is a PID Lo Limit. 
     
     
         13 . The system of  claim 11 , wherein the controller is configured to:
 determine whether the actual pressure drops below a third pressure which is less than the second pressure while the motor is in the sleep mode; and   respond to the actual pressure dropping below the third pressure by causing the motor to exit the sleep mode.   
     
     
         14 . The system of  claim 13 , wherein the controller is configured to determine whether the actual pressure drops below the third pressure by computing a pressure error between the actual pressure and the third pressure and determining whether the pressure error is greater than zero. 
     
     
         15 . The system of  claim 11 , wherein the controller is configured to determine whether the actual pressure remains above the second pressure by computing a pressure error between the actual pressure and the second pressure and determining whether the pressure error is greater than zero. 
     
     
         16 . The system of  claim 11 , wherein the sleep mode determination further comprises responding to the actual pressure dropping below the second pressure during the second timer by exiting the sleep mode determination. 
     
     
         17 . The system of  claim 11 , wherein the controller is configured to control the operating frequency of the motor by controlling the inverter to vary power provided to the motor. 
     
     
         18 . The system of  claim 11 , wherein the duration of the second timer is based upon the operating frequency of the motor when the first timer has elapsed. 
     
     
         19 . The system of  claim 18 , wherein a range of the operating frequency extends from the low frequency to a high frequency, the range being divided into a plurality of zones, and the duration of the second timer is based upon which of the plurality of zones the operating frequency of the motor falls when the first timer has elapsed. 
     
     
         20 . A non-transitory computer-readable medium with an executable program stored thereon for controlling a motor in a liquid system, wherein the program instructs a controller to perform the following steps:
 control an operating frequency of the motor to cause a pump to maintain an actual pressure of liquid in the liquid system at or near a first pressure for a first timer; and   respond to a determination that the first timer has elapsed by initiating a sleep mode determination, comprising:
 ramping the operating frequency to a low frequency;
 determining whether the actual pressure remains above a second pressure which is less than the first pressure for a second timer; and 
 
 responding to the actual pressure remaining above the second pressure for the second timer by causing the motor to enter a sleep mode. 
   
     
     
         21 . The non-transitory computer readable medium of  claim 20 , wherein the low frequency is a PID Lo Limit. 
     
     
         22 . The non-transitory computer readable medium of  claim 20 , wherein the program further instructs the controller to:
 determine whether the actual pressure drops below a third pressure which is less than the second pressure while the motor is in the sleep mode; and   respond to the actual pressure dropping below the third pressure by causing the motor to exit the sleep mode.   
     
     
         23 . The non-transitory computer readable medium of  claim 22 , wherein the controller determines whether the actual pressure drops below the third pressure by computing a pressure error between the actual pressure and the third pressure and determining whether the pressure error is greater than zero. 
     
     
         24 . The non-transitory computer readable medium of  claim 20 , wherein the controller determines whether the actual pressure remains above the second pressure by computing a pressure error between the actual pressure and the second pressure and determining whether the pressure error is greater than zero. 
     
     
         25 . The non-transitory computer readable medium of  claim 20 , wherein the sleep mode determination further comprises responding to the actual pressure dropping below the second pressure during the second timer by exiting the sleep mode determination.