HVAC custom control system

• US 6,227,961 B1
• Filed: 01/14/1999
• Issued: 05/08/2001
• Est. Priority Date: 05/21/1998
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Brown, Michael C., Moore, Scott W., Webb, Terry L.
• Primary Examiner(s): Joyce, Harold
• Application Number:
  US09/231,050
• Time in Patent Office: 845 Days
• Field of Search: 454/229, 454/236, 236/49.3
• US Class Current: 454/229
• CPC Class Codes: F04D 27/004 by varying driving speed
• CPC Class Codes: F05D 2260/85 Starting
• CPC Class Codes: F24F 11/77 by controlling the speed of ventilators
• CPC Class Codes: F24F 2110/30 Velocity
• CPC Class Codes: F24F 2110/40 Pressure, e.g. wind pressure
• CPC Class Codes: F24F 2140/10 Pressure
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

A fan control system suitable for use in air moving applications has a pressure sensor responsive to an air pressure in an air duct for supplying a static pressure signal representative of the air pressure. A supply air flow sensor is responsive to an air flow in a supply air duct and supplies a supply air flow signal representative of the air flow in the supply air duct. A return air flow sensor is responsive to an air flow in a return air duct and supplies a return air flow signal representative of the air flow in the return air duct. A supply fan moves air in the supply air duct. The supply fan is driven by a supply fan motor. A return fan moves air in the return air duct. The return fan is driven by a return fan motor. A unitary volumetric air flow controller is connected to the supply fan motor and to the return fan motor. The air flow controller selectively applies a supply drive power signal to the supply fan motor to energize the supply fan motor, and selectively applies a return drive signal to the return fan motor to energize the return fan motor. The power drive signals are responsive to the static pressure signal, supply air flow signal, and return air flow signal.

Claims

1. A fan control system suitable for use in air moving applications comprising:

a pressure sensor responsive to an air pressure in a supply air duct for supplying a static pressure signal representative of the static air pressure in the supply air duct;

a supply air flow sensor responsive to an air flow in a supply air duct for supplying a supply air flow signal representative of the air flow in the supply air duct;

a return air flow sensor responsive to an air flow in a return air duct for supplying a return air flow signal representative of the air flow in the return air duct;

a supply fan for moving air in the supply air duct, said supply fan being driven by a supply fan motor;

a return fan for moving air in the return air duct, said return fan being driven by a return fan motor; and

a unitary volumetric air flow controller connected to the supply fan and connected to the return fan, said air flow controller comprising;

a drive controller selectively controlling the supply fan and the return fan;

a process controller selectively providing a drive control signal to the drive controller in response to the static pressure signal, the supply air flow signal, and the return air flow signal, said drive controller and said process controller being mounted in a common housing; and

wherein the drive controller is responsive to the drive control signal for selectively applying a supply drive power signal to the supply fan for energizing the supply fan, and for selectively applying a return drive signal to the return fan motor for energizing the return fan motor, whereby the static pressure in the supply air duct is maintained at a substantially constant pressure.

2. The fan control system of claim 1 wherein the supply drive signal is responsive to the static pressure signal whereby a constant pressure is maintained in the supply air duct.

3. The fan control system of claim 1 wherein the drive controller further comprises a modulator for modulating the return drive power signal as a function of the supply air flow signal and the return air flow signal.

4. The fan control system of claim 1 further comprising a set point control panel for providing an operator access to at least one operator control input.

5. The fan control system of claim 1 wherein the unitary volumetric air flow controller includes one or more controls for simultaneously providing static pressure control of air flow within the system, volumetric flow synchronization of air flow rates with the system, and drive control of the fans.

6. The fan control system of claim 1 wherein the unitary volumetric air flow controller includes operator adjustable controls including a hand-off-auto switch, an inverter/bypass selector and/or a test-isolate-normal switch.

13. The fan control system of claim 2 wherein the anti-windmilling time period is fixed.

7. A fan control system suitable for use in air moving applications comprising:

a pressure sensor responsive to an air pressure in an air duct for supplying a static pressure signal representative of the air pressure;

a supply air flow sensor responsive to an air flow in a supply air duct for supplying a supply air flow signal representative of the air flow in the supply air duct;

a return air flow sensor responsive to an air flow in a return air duct for supplying a return air flow signal representative of the air flow in the return air duct;

a supply fan for moving air in the supply air duct, said supply fan being driven by a supply fan motor;

a return fan for moving air in the return air duct, said return fan being driven by a return fan motor; and

a volumetric air flow controller connected to the supply fan and connected to the return fan, said air flow controller for selectively applying a supply drive power signal to the supply fan motor for energizing the supply fan motor and for selectively applying a return drive signal to the return fan motor for energizing the return fan motor, said power drive signals being responsive to the static pressure signal, supply air flow signal, and return air flow signal, and said air flow controller further comprising an anti-windmilling controller for applying a braking signal to the supply fan motor.

8. The fan control system of claim 7 wherein the braking signal is applied to the supply fan motor when the supply drive power signal is not applied to the supply fan motor, said braking signal being applied for an anti-windmilling time period sufficient to ensure that a windmilling supply fan is brought to rest prior to applying the supply drive power signal.

9. The fan control system of claim 8 wherein the anti-windmilling time period is fixed.

10. The fan control system of claim 8 wherein the anti-windmilling controller further comprises rotation detection means responsive to a direction of rotation of the supply fan for providing a supply fan direction signal representative of the direction of rotation of the supply fan, such that when the supply fan direction signal indicates that the supply fan is rotating in a reverse direction, the braking signal comprises a dc injection signal.

12. The fan control system of claim 8 wherein the braking signal is applied to the return fan motor when the return drive power signal is not applied to the return fan motor, said braking signal being applied for an anti-windmilling time period sufficient to ensure that a windmilling return fan is brought to rest prior to applying the return drive power signal.

14. The fan control system of claim 8 wherein the anti-windmilling controller further comprises rotation detection means responsive to a direction of rotation of the return fan for providing a return fan direction signal representative of the direction of rotation of the return fan, such that when the return fan direction signal indicates that the return fan is rotating in a reverse direction, the braking signal comprises a dc injection signal.

11. A fan control system suitable for use in air moving applications comprising:

a pressure sensor responsive to an air pressure in an air duct for supplying a static pressure signal representative of the air pressure;

a supply air flow sensor responsive to an air flow in a supply air duct for supplying a supply air flow signal representative of the air flow in the supply air duct;

a return air flow sensor responsive to an air flow in a return air duct for supplying a return air flow signal representative of the air flow in the return air duct;

a supply fan for moving air in the supply air duct, said supply fan being driven by a supply fan motor;

a return fan for moving air in the return air duct, said return fan being driven by a return fan motor; and

a volumetric air flow controller connected to the supply fan and connected to the return fan, said air flow controller for selectively applying a supply drive power signal to the supply fan motor for energizing the supply fan motor and for selectively applying a return drive signal to the return fan motor for energizing the return fan motor, said power drive signals being responsive to the static pressure signal, supply air flow signal, and return air flow signal, and said air flow controller further comprising an anti-windmilling controller for applying a braking signal to the return fan motor.

15. A fan control system suitable for use in air moving applications comprising:

a pressure sensor responsive to an air pressure in an air duct for supplying a static pressure signal representative of the air pressure;

a supply air flow sensor responsive to an air flow in a supply air duct for supplying a supply air flow signal representative of the air flow in the supply air duct;

a return air flow sensor responsive to an air flow in a return air duct for supplying a return air flow signal representative of the air flow in the return air duct;

a supply fan for moving air in the supply air duct, said supply fan being driven by a supply fan motor;

a return fan for moving air in the return air duct, said return fan being driven by a return fan motor; and

a volumetric air flow controller connected to the supply fan and connected to the return fan, said air flow controller for selectively applying a supply drive power signal to the supply fan motor for energizing the supply fan motor and for selectively applying a return drive signal to the return fan motor for energizing the return fan motor, said power drive signals being responsive to the static pressure signal, supply air flow signal, and return air flow signal, and the volumetric air flow controller being responsive to an adjustable potentiometer for controlling injection braking of the fans to minimize windmilling.

16. A fan control system suitable for use in air moving applications comprising:

a pressure sensor responsive to an air pressure in an air duct for supplying a static pressure signal representative of the air pressure;

a supply air flow sensor responsive to an air flow in a supply air duct for supplying a supply air flow signal representative of the air flow in the supply air duct;

a return air flow sensor responsive to an air flow in a return air duct for supplying a return air flow signal representative of the air flow in the return air duct;

a supply fan for moving air in the supply air duct, said supply fan being driven by a supply fan motor;

a return fan for moving air in the return air duct, said return fan being driven by a return fan motor; and

a volumetric air flow controller connected to the supply fan and connected to the return fan, said air flow controller for selectively applying a supply drive power signal to the supply fan motor for energizing the supply fan motor and for selectively applying a return drive signal to the return fan motor for energizing the return fan motor, said power drive signals being responsive to the static pressure signal, supply air flow signal, and return air flow signal, and said volumetric air flow controller including an open loop motor control for controlling injection braking of the fans to minimize windmilling.