subject: Ab Converters Pf400 In The Central Air Conditioning System Design And Application Of [print this page] I. Introduction Most of the buildings in a year, only several tens day oersted time, central air conditioning in the maximum load. Central air conditioning cooling loads, always in dynamic change, such as morning and evening, alternating on a quarterly basis, annual cycle of environmental and human factors have immediate impact on the central air conditioning cooling loads. General, the cooling load in the range of 5 to 60% fluctuations, most of the buildings at least 70% of the time each year is in this situation. Most central air conditioning, because the majority of system design with maximum cooling load for the maximum power drive. In this way, they often cause the actual needs of the cooling load and the maximum power output of the contradiction between the actual cause great waste of energy to cause a huge user electricity charges, increased operating costs, reduce business competitiveness.
This article describes AB Inverter PF400 water cycle in the central air-conditioning systems, fans and cooling tower fan variable frequency in the design and application.
2, PF400 water circulation in the central air conditioning system design
Central air conditioning system water system is divided into chilled water (or water) circulation, cooling water circulation system, intelligent frequency conversion control cabinet main target for the chilled water (hot water) circuit and the cooling water circuit.
1, the control of frozen water cycle
From the frozen pump and chilled water piping component, outflow from the chiller chilled water chilled by the chilled water pump pressure into the pipeline, in a heat exchange within the room, take away the heat inside the room, so room temperature decline.
Chilled water pump control mode are: top (or the most negative side) pressure control
At the top of the central air conditioning system, air conditioning because each layer corresponds to changes in heat load of cold water inlet valves open and close, thus regulating temperature. As the chilled water flow constantly changing, the highest levels of hydraulic pressure caused by larger changes in order to solve the problem, the need to control a cooling pump valve, hydraulic pressure to maintain the highest level roughly constant, but most applications are maintained water valve opening some, any change with pressure. If so, will lead to pressure loss and low efficiency. At this point the use of a speed control to maintain optimum pressure, prevents pressure loss and a more substantial increase in energy efficiency and to achieve good results.
2, cooling water control By the cooling pump and cooling water piping and cooling tower component. Chiller for heat exchange, is the cooling water temperature at the same time, will release a lot of heat. The heat absorbed by cooling water is cooling water temperature. Cooling pumps will be promoted to the temperature cooling water into the cooling tower, so that the cooling tower heat exchange with the atmosphere, and then lower and lower the temperature of cooling water, get back to chillers. This constant cycle of heat released chiller away.
Cooling water pump control mode as follows: temperature difference control.
As the water temperature is cooling tower with ambient temperature change, and its unilateral freezing temperature can not accurately reflect the amount of heat units. Therefore, cooling water pump to water and backwater of the difference in temperature as a control based on water and return water to achieve constant temperature difference between the control is more reasonable. Temperature difference, which meant that the heat generated by a large refrigeration unit, should increase the speed of the cooling pump, cooling water circulation rate increases; the contrary, you should reduce speed.
3, inverter control principle Can see from the above analysis, water recycling system for central air conditioning inverter control is generally poor or constant temperature with constant pressure differential closed-loop control, PF400 Inverter Has a built-in PID control loop, used to make the feedback process the pressure difference or temperature difference is consistent with the set value.
In PF400 the PID control, the ratio of output control operation is the ratio between volume and bias.
