Motor drive circuit for pressure control of a pumping system
First Claim
1. A liquid supply system comprisinga) a motor-pump unit including a variable speed electric motor;
- b) a pipe connected to said unit for conveying liquid pumped by said unit;
c) a pressure sensor connected to said pipe for providing a pressure signal representative of the liquid pressure in said pipe; and
d) unit operating apparatus responsive to said pressure signal and connected to said unit for operating said unit, said apparatus comprising1) speed control means for operating said unit in a first mode wherein the speed of said unit is adjusted to maintain a substantially constant pressure in said pipe, said speed control means being connected to said pressure sensor and to said unit;
2) speed change means for operating said unit in a second mode wherein the speed of said unit is reduced;
3) pressure monitoring means responsive to said pressure sensor for providing an indication of a drop of pressure in said pipe; and
4) intermittent means connected to said monitoring means for normally operating said unit in said first mode, for intermittently operating said unit in said second mode, and for turning off said unit when said monitoring means fails to indicate a drop of pressure when said unit is operating in said second mode.
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Accused Products
Abstract
This disclosure relates to a liquid supply system including a motor-pump unit designed for installation in a liquid supply such as a well or storage tank. The unit supplies the liquid to a supply pipe, and a pressure sensor connected to the pipe is operable to provide a control signal representative of the liquid pressure in the pipe. The motor is a variable-speed AC motor. A control for the motor is responsive to the control signal and actuates a power circuit to drive the motor at a speed adjusted to maintain the liquid pressure at a substantially constant value. The control circuit further includes means for turning off the power to the motor in the absence of flow through pipe, which does not require a flow sensor. The power circuit comprises a DC link including a rectifier and an inverter. The rectifier is located adjacent the pressure sensor; the inverter may be located adjacent the rectifier and the pressure sensor or in the casing of the motor-pump unit.
214 Citations
9 Claims
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1. A liquid supply system comprising
a) a motor-pump unit including a variable speed electric motor; -
b) a pipe connected to said unit for conveying liquid pumped by said unit; c) a pressure sensor connected to said pipe for providing a pressure signal representative of the liquid pressure in said pipe; and d) unit operating apparatus responsive to said pressure signal and connected to said unit for operating said unit, said apparatus comprising 1) speed control means for operating said unit in a first mode wherein the speed of said unit is adjusted to maintain a substantially constant pressure in said pipe, said speed control means being connected to said pressure sensor and to said unit; 2) speed change means for operating said unit in a second mode wherein the speed of said unit is reduced; 3) pressure monitoring means responsive to said pressure sensor for providing an indication of a drop of pressure in said pipe; and 4) intermittent means connected to said monitoring means for normally operating said unit in said first mode, for intermittently operating said unit in said second mode, and for turning off said unit when said monitoring means fails to indicate a drop of pressure when said unit is operating in said second mode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A liquid supply system comprising
a) a motor-pump unit including a variable speed electric motor; -
b) a pipe connected to said unit for conveying liquid pumped by said unit; c) a pressure sensor connected to said pipe for providing a pressure signal representative of the liquid pressure in said pipe; and d) apparatus responsive to said pressure signal and to said unit for operating said unit, said apparatus comprising 1) speed control means responsive to said pressure signal and connected to said unit for operating said unit to maintain a substantially constant pressure in said pipe; 2) speed change means periodically connected to said unit for reducing the speed of said unit; and 3) pressure monitoring means responsive to said pressure signal for turning off said unit if a periodic reduction in the speed of said unit does not produce a pressure drop.
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Specification