System and method for controlling a variable speed compressor during stopping
AssigneeIngersoll-Rand Company
InventorsJames R. Lindsey, James D. Mehaffey, Richard Mauney
Life of this patent
Estimating the term…
Abstract
A compressor system operable to shutdown in response to a shutdown signal. The compressor system includes a compression device operable between a first speed and a second speed to produce a flow of compressed fluid at a pressure. A blowdown valve is movable between a closed position and an open position in which at least a portion of the flow of compressed fluid passes through the blowdown valve to reduce the pressure of the flow of compressed fluid. A sensor is positioned to measure the pressure and a controller is operable to move the blowdown valve to the open position and set the speed of the compression device to a low set point speed in response to the shutdown signal.
Claims20
A compressor system operable to shutdown in response to a shutdown signal, the compressor system comprising:
- a compression device including a fluid intake and a fluid output, the compression device operable between a first speed and a second speed to produce a flow of compressed fluid at an output pressure from a flow of fluid at an intake pressure;
- a blowdown valve positioned downstream from a lubricant/fluid separator and movable between a closed position and an open position in which at least a portion of the flow of compressed fluid passes through the blowdown valve to reduce the output pressure of the flow of compressed fluid;
- a sensor positioned to measure a downstream pressure and generate the shutdown signal in response to a measured downstream pressure in excess of a predetermined pressure;
- and
- a controller operable to move the blowdown valve to the open position and set the speed of the compression device to a low set point speed in response to the shutdown signal, in order to decrease the output pressure to a level below the operating pressure range;
- and
- further comprising a timer operable to monitor the passage of time, and wherein the controller reduces the compression device speed to a third speed below the low set point speed in response to the passage of a first predetermined period of time.
A compressor system comprising:
- a compression device including a variable speed drive coupled to a compressor having a fluid intake, a fluid output, and a sump, the compression device operable between a first speed and a second speed to produce a flow of compressed fluid at an output pressure from a flow of fluid at an intake pressure;
- a blowdown valve movable between a closed position and an open position in which at least a portion of the flow of compressed fluid passes through the blowdown valve to reduce the output pressure of the flow of compressed fluid;
- a pressure sensor positioned to measure a downstream pressure of the flow of compressed fluid;
- a sump pressure sensor positioned to measure a sump pressure within the sump;
- and a controller operable to:
- move the blowdown valve to the open position,
- set the speed of the compression device to a low set point speed in response to a measured downstream pressure of the flow of compressed fluid in excess of a predetermined pressure, and one of
- reduce the speed of the compression device from the low set point speed to a third speed lower than the low set point speed in response to the passage of a predetermined length of time and reduce the speed of the compression device from the low set point speed to zero in response to a measured sump pressure below a predetermined sump pressure, in order to decrease the output pressure to a level below the operating pressure range;
- and
- wherein the controller reduces the speed of the compression device from the third speed to zero in response to the passage of a second predetermined length of time, the second predetermined length of time starting in response to the passage of the predetermined length of time.
A method of shutting down operation of a compressor while preventing backflow through the compressor, the compressor having a compression stage that, in operation between first and second operating speeds, maintains a pressure of a fluid flowing therethrough within an operating pressure range, the method comprising:
- sensing a compressed fluid pressure downstream of the compression stage;
- sending a signal indicative of the compressed fluid pressure to a controller;
- starting a shutdown timer at an initial value in response to the signal;
- opening a blowdown valve positioned downstream of the compression stage to relieve compressed fluid pressure in response to the signal;
- setting the compressor speed to a speed lower than the first and second operating speeds in response to a sensed compressed fluid pressure in excess of a predetermined pressure;
- and
- sending a stop signal from the controller to a variable frequency drive to stop the compressor when the shutdown timer reaches a final value, such that the downstream pressure decreases to a level below the operating pressure range;
- and
- further comprising reducing the compressor speed to a speed below the lower speed when the shutdown timer reaches a slow down time between the initial value and the final value of the timer.
Dependencies are inferred from the claim text.