Background technology
Existing modular water chilling unit group, control system generally comprise MCU (microprocessor) and discharge testing circuit.Whether normal in order to detect circulation work, most employing detects the disconnection of discharge switch by alternating current or closure signal realizes start, protects or shuts down, thereby reaches the purpose of control or protection system.The discharge switching signal needs to adopt power resistor to carry out current limliting in transmission course, needs the coupling shaping circuit to carry out the signal level shaping.The control system of prior art, discharge testing circuit complex structure not only, and since the transmission be AC signal, be easy to generate induced electromotive force in the transmission course, cause discharge switch false retrieval and erroneous judgement, particularly for the multicomputer centralized control system, because signal transmission wire is long, and, more be easy to generate mistake through twining.
The control method of prior art is, after system's unit was opened, before compressor was opened, main frame output water pump control signal was opened water pump, judged then whether the discharge switch is closed, if closed, then the compressor of each unit is opened and freezed or heat; If the discharge switch is not closed, then think system's lack of water, can not open compressor.Disconnect if after compressor is opened, the discharge switch occurs, then report fault after the close compressor, could open unit after re-powering after whole system must be repaired.This control method can not be distinguished the circulation fault (stifled, dirty stifled etc. as lack of water, ice) or the fault of discharge switch itself, needs to carry out artificial forced shutdown and start without exception.
Summary of the invention
Technical problem to be solved by this invention just provides and a kind ofly adopts direct current signal to detect the control system of discharge and improve its control method.
The present invention solve the technical problem, and the technical scheme of employing is,
Water chilling unit control method may further comprise the steps:
A. whether before starting mode of pump, it is closed to detect the discharge switch, if, ingoing stream amount switch abnormal protection program then, whole system can't be started shooting; Otherwise enter following step;
B. after starting water pump t1 minute,, then switch off the pump earlier if in t2 minute, detect less than the discharge switch closure signals, after starting water pump t1 minute once more, if detected less than the discharge switch closure signals in t2 minute continuously again, cut off the electricity supply ingoing stream amount abnormal protection program immediately;
C. normal operation period, if t does not detect the discharge switch closure signals second continuously, shutdown system immediately then, ingoing stream amount abnormal protection program.
Further, after the ingoing stream amount abnormal protection program, control system is sent prompting.
Further, after the ingoing stream amount abnormal protection program, system can not recover voluntarily; Have only by after repairing, re-power start and just can resume operation.
The invention has the beneficial effects as follows, the accurate fault message of circulation can be provided control system, reduced and thought the loss of shutting down, improved the reliability of system.
The specific embodiment
Describe technical scheme of the present invention in detail below in conjunction with drawings and Examples.
The present invention adopts dc current signal transmission detection signal, according to the DC current characteristic, can cancel waveform shaping circuit, can reduce cost, improves reliability.By controlling after the detection to the discharge switch, after powering on, do not start water pump before, if to detect the discharge switch be closure signal, then report the discharge switch unusual, system can not start shooting; If behind the starting mode of pump, detect the discharge switch for disconnecting, then switch off the pump earlier, start water pump after 3 minutes again, if detect the discharge switch, then report discharge unusual still for disconnecting; Must could start shooting again through repairing the back system.Can judge automatically that so the fault of discharge switch own still is system's excessive low water level protection.
Embodiment
This routine control system comprises MCU and discharge testing circuit, as shown in Figure 1.The discharge testing circuit is by+20V power supply, photoelectrical coupler D1, and resistance R 1, R2, capacitor C 1, discharge switch SW 1 is formed.The circuit working principle is as follows:
When discharge switch SW 1 disconnected, flowing through the electric current that 1,2 pin of resistance R 1, photoelectrical coupler D1 flow through was 0, and 3,4 pin of photoelectrical coupler D1 end, and are in off-state, the SW input of MCU pulled on the resistance R 2 high level (+5V).Capacitor C 1 has filter action, makes the level signal that enters MCU clean and noiseless, and resistance R 1 has metering function.When discharge switch SW 1 was connected, the electric current that flows through 1,2 pin of resistance R 1 and photoelectrical coupler D1 was about 4mA, 3, the 4 pin saturation conductions of photoelectrical coupler D1, and the SW input of MCU is changed to low level.The existing buffer action of photoelectrical coupler D1 also has the level conversion effect concurrently, and the 20V dc level signal is converted to the 5V dc level signal.
Like this, no matter how long lead from discharge switch SW 1 to photoelectrical coupler D1 has, also no matter the whether winding of lead can not produce because the detection mistake that lead length and canoe cause has improved the reliability that detects widely.
System control method is as follows:
System architecture is referring to Fig. 2, and Fig. 2 is the system that N platform unit is formed.1 is main frame among the figure; 2 is water pump; 3 is discharge switch 1; 4 is discharge switch N; 5 is control system.
At first, before water pump 2 starts, if detect discharge switch 3,4 closures, then ingoing stream amount switch abnormal protection program.Explanation is not before water pump 2 starts, and promptly chilled water does not flow, and discharge switch 3,4 should disconnect, if closed, it is unusual to illustrate that then discharge switch 3,4 occurs itself, rather than excessive low water level protection, and whole system can not be started shooting.
Second step; in water pump 2 starts back 3 minutes; if detected signal in continuous 1 minute less than discharge switch 3,4 closures; then switch off the pump 2 earlier; restart water pump 2 then; if detected the signal less than discharge switch 3,4 closures, ingoing stream amount abnormal protection program immediately in continuous again 1 minute.Lack of water in the water system is described, perhaps water system has obstruction.
In the 3rd step, after starting mode of pump 2 moves 3 minutes, do not detect discharge switch 3,4 closure signal, then first Shutdown Hosts 1 and water pump 2, ingoing stream amount abnormal protection program as continuous 10 seconds.The fault of water system own is described.
The 4th step, under second and third step situation, the glittering indication fault of the malfunction indicator lamp of control system 5 position, and close compressor, blower fan and water pump 2.
In the 5th step, after the discharge abnormal protection occurred 2 times, system can not recover automatically, had only by after repairing, and re-powered start and could recover normal operation.
Above-mentioned time parameter can be set as pump capacity, pipe condition etc. according to concrete systematic parameter, reduces erroneous judgement as far as possible.
Control method of the present invention; not only can solve because the system failure that the fault of discharge switch itself causes; can solve again and cause chilled water in a few minutes, can't finish circulation wrong report failure problems under the situation such as water system lack of water; having avoided the people is the drawback of carrying out startup and shutdown, fault has only taken place completely just can report the discharge abnormal protection.For multicomputer water system in parallel, coordinate the operation of other units by Centralized Controller 5.