VARIABLE SPEED DRIVE WITH PULSE-WIDTH MODULATED SPEED CONTROL

• US 20100083693A1
• Filed: 10/02/2009
• Published: 04/08/2010
• Est. Priority Date: 10/03/2008
• Status: Active Grant

• Current Assignee: Johnson Controls Tyco IP Holdings LLP (Johnson Controls International plc)
• Original Assignee: Johnson Controls Technology Company (Johnson Controls International plc)
• Inventors: Dubey, Kanishk, Warner, Justin Drew, Wu, Zhiqiao, Slothower, Scott V., Jadric, Ivan, Borisov, Konstantin, Adiga-Manoor, Shreesha, Todd, Michael S., Hansen, John C.
• Granted Patent: US 8,336,323 B2
• Time in Patent Office: Days
• US Class Current: 62/498
• CPC Class Codes: F25B 2600/0253 with variable speed
• CPC Class Codes: F25B 49/025 Motor control arrangements
• CPC Class Codes: H02P 6/085 in a bridge configuration
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

A drive system for a compressor of a chiller system includes a variable speed drive. The variable speed drive receives an input AC power at a fixed input AC voltage and a fixed input frequency, and provides an output AC power at a variable voltage and variable frequency. The variable speed drive includes a converter connected to an AC power source. The converter is arranged to convert the input AC voltage to a DC voltage. A DC link is connected to the converter and configured to filter and store the DC voltage from the converter. An inverter is connected to the DC link. A motor is connectable to the compressor for powering the compressor. A controller is arranged to control switching in the converter and the inverter. The controller is arranged to apply randomized pulse width modulation to vary the switching frequency of transistors in the converter and the inverter at each switching cycle. The motor may be a permanent magnet synchronous motor.

Claims

1. A system for powering a compressor of a chiller system, drive system comprising:

a variable speed drive, the variable speed drive being configured to receive a fixed input AC voltage and provide an output AC power at a variable voltage and variable frequency, the variable speed drive comprising;

a converter connected to an AC power source providing the input AC voltage, the converter being configured to convert the input AC voltage to a DC voltage;

a DC link connected to the converter, the DC link being configured to filter and store the DC voltage from the converter ; and

an inverter connected to the DC link;

a motor connectable to the compressor for powering the compressor; and

a controller configured to control switching of switches in the converter and the inverter, the controller configured to apply randomized pulse width modulation to vary the switching frequency of the switches in the converter and the inverter at each switching cycle.

2. The system of claim 1, wherein the motor is a permanent magnet synchronous motor.

3. The system of claim 1, wherein the controller is further configured to apply randomized pulse width modulation to reduce a magnitude of harmonic components present in a line current and a line voltage of the motor.

4. The system of claim 1, wherein the controller is further configured to apply randomized pulse width modulation to reduce the level of the electromagnetic interference and the level of acoustic noise generated by the drive system.

5. The system of claim 1, wherein the controller is further configured to apply randomized pulse width modulation to reduce the magnitude of the electromagnetic noise through reduction of the harmonic currents in a high frequency range.

6. The system of claim 2, wherein the permanent magnet synchronous motor further comprises a plurality of permanent magnets positioned in multiple pole arrangements on a rotor portion.

7. The system of claim 6, wherein the plurality of permanent magnets being adhesively affixed to a rotor cage, the plurality of permanent magnets enveloped by a sleeve to maintain the plurality of permanent magnets in contact with the rotor cage when centrifugal forces act on the rotor portion during rotation.

8. The system of claim 7, wherein the rotor cage is a cylindrical steel rotor cage.

9. The system of claim 7, wherein the sleeve comprises a flexible, high strength, magnetically non-permeable material.

10. The system of claim 9, wherein the material is carbon fiber tubular sheet material or stainless steel.

11. The system of claim 1, wherein the controller is further configured to apply a randomized sampling of sampling feedback current and voltage values for a closed loop control operation for randomized pulse width modulation.

12. A vapor compression system comprising:

a compressor, a condenser, and an evaporator connected in a closed refrigerant loop;

a motor connected to the compressor to power the compressor; and

a variable speed drive connected to the motor, the variable speed drive being configured to receive an input AC power at a fixed input AC voltage and a fixed input frequency and provide an output power at a variable voltage and variable frequency to the motor, the variable voltage having a maximum voltage greater in magnitude than the fixed input AC voltage and the variable frequency having a maximum frequency greater than the fixed input frequency, the variable speed drive comprising;

a converter connected to an AC power source, the converter being configured to convert the fixed input AC voltage to a DC voltage;

a DC link connected to the converter, the DC link being configured to filter and store the DC voltage from the converter ; and

an inverter connected to the DC link; and

a controller configured to control switching of switches in the converter and the inverter, the controller configured to apply randomized pulse width modulation to vary the switching frequency of switches in the converter and the inverter at each switching cycle.

13. The chiller system of claim 12, wherein the motor is a permanent magnet synchronous motor.

14. The chiller system of claim 12, wherein the controller is further configured to apply randomized pulse width modulation to reduce a magnitude of harmonic components present in a line current and a line voltage of the motor.

15. The chiller system of claim 12, wherein the controller is further configured to apply randomized pulse width modulation to reduce the level of the electromagnetic interference and the level of acoustic noise generated by the drive system.

16. The chiller system of claim 12, wherein the controller is further configured to apply randomized pulse width modulation to reduce the magnitude of the electromagnetic noise through reduction of the harmonic currents in high frequency range

17. A method of controlling a variable speed drive having a converter, a DC link, and an inverter, the method comprising:

providing an inverter connected to a DC link, the inverter configured to power a corresponding load; and

generating a randomized switching signal for the inverter, the randomized switching signal being operable to activate and deactivate the inverter to obtain a preselected output power and a preselected output frequency from the inverter.