JP-2020535373-A5 -

Dates

Publication Date

20221214

Application Date

20180924

Description

Cross-reference of related applications This application claims the benefit of and priority thereto of U.S. Provisional Patent Application No. 62/563,039, filed on 25 September 2017, the entire disclosure of which is incorporated herein by reference. The building may include a heating, ventilation, and air conditioning (HVAC) system. This is a perspective view of a chiller assembly according to some embodiments. Figure 1 is an elevation view of a chiller assembly according to one embodiment. This is a schematic diagram of a variable-speed drive device that may be used in the chiller assembly shown in Figure 1 according to some embodiments. This is a flowchart of the input current estimation and control process that can be performed by the variable speed drive device shown in Figure 3, according to some embodiments. This disclosure generally relates to the input current control function of a variable speed drive (VSD). A VSD can provide power with variable voltage and frequency to an electric motor. A VSD may have an output current rating higher than its input current rating. For example, a VSD with an output current rating of 420 amperes may have an input current rating of 390 amperes, and a VSD with an output current rating of 780 amperes may have an input current rating of 600 amperes. A VSD with a rated frequency of 60 Hz may operate by measuring the output current and assuming that the input current is the same, but this assumption does not work well for VSDs with higher frequency ratings (e.g., 110 Hz, 210 Hz). In addition, when a VSD is implemented in a chiller assembly, optimal performance of the chiller assembly is achieved when the output current rating and input current rating are different. This specification describes systems and methods for estimating the VSD input current using existing VSD sensors and circuits. Referring generally to the drawings, a chiller assembly having a VSD operating according to an input control system is shown. Referring particularly to Figure 1, an exemplary implementation of chiller assembly 100 is shown. The chiller assembly 100 may include a compressor 102 driven by an electric motor 104, a condenser 106, and an evaporator 108. The refrigerant circulates through the chiller assembly 100 in a closed refrigerant circuit of the vapor compression cycle. The chiller assembly 100 may also include a control panel 114 for controlling the operation of the vapor compression cycle within the chiller assembly 100. The electric motor 104 can be powered by the VSD 110. The VSD 110 receives alternating current (AC) power with a specific fixed line voltage and fixed line frequency from an AC power source (see Figure 2 below) and provides the electric motor 104 with power having a variable voltage and frequency. The VSD 110 can provide the electric motor 104 with AC power having a voltage and frequency higher and lower than the rated voltage and frequency of the electric motor 104. The electric motor 104 can be any type of electric motor that can be powered by the VSD 110. For example, the electric motor 104 may be a high-speed induction motor. The compressor 102 is driven by the electric motor 104 to compress the refrigerant vapor received from the evaporator 108 via the suction line 112 and to send the refrigerant vapor to the condenser 106 via the discharge line 124. The compressor 102 may be a centrifugal compressor, a screw compressor, a scroll compressor, a turbine compressor, or any other suitable type of compressor. The evaporator 108 includes an internal tube bundle, a supply line 120 for supplying process fluid to the internal tube bundle, and a return line 122 for discharging process fluid from the internal tube bundle. The supply line 120 and the return line 122 may be in fluid communication with components within the HVAC system (e.g., air handlers) via conduits for circulating the process fluid. The process fluid is a coolant for cooling the building and may be, but is not limited to, water, ethylene glycol, calcium chloride brine, sodium chloride brine, or any other suitable liquid. The evaporator 108 is configured to lower the temperature of the process fluid as it passes through the tube bundle of the evaporator 108 and exchanges heat with the coolant. Coolant vapor is formed within the evaporator 108 by the coolant liquid being sent to the evaporator 108, exchanging heat with the process fluid, and undergoing a phase change to coolant vapor. The refrigerant vapor sent to the condenser 106 by the compressor 102 transfers heat to the fluid. As a result of heat transfer with the fluid, the refrigerant vapor condenses in the condenser 106 to become liquid refrigerant. The liquid refrigerant from the condenser 106 flows through the expansion device and returns to the evaporator 108, completing the refrigerant cycle of the chiller assembly 100. The condenser 106 includes a supply line 116 and a return line 118 for circulating the fluid between the condenser 106 and exte