Technical Analysis and Application of Frequency Converter in Circulating Water Pump
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The condenser needs to adjust the size of the water flow according to the circulating water temperature so as to control the exhaust steam of the steam turbine. Therefore, the circulating water pump is not always in a full-load working condition. The pressure, traffic has a certain margin. The pump shaft power is proportional to the cube of its speed. So the speed slightly lower the power that is more substantial decline. In more than one pump, such as one of the use of frequency converter adjustment, according to changes in temperature and load at any time to adjust the water flow to achieve energy-saving purposes. Circulating pump motor power 185kW. Hitachi i300 series configuration 2200HF inverter, taking into account the motor soft-start longer, so as a long-term operation of the pump, the design of spare pump self-cast circuit and alarm loop. Select inverter fault alarm output contact AL0, AL1, as the backup pump since the vote contact, due to the smaller contact capacity. DC DC voltage is low (AC250V, 0.2A, DC30V, 0.6A inductive load), so in the output port of a DZ-52/40 type relay ZJ, to solve the contact capacity of small and insufficient number of issues. ZJ's three mating contacts are respectively connected to the movable contact of BCJ of three standby pump outlet protection relays. When the inverter trips due to overcurrent, overvoltage, overload and other reasons, the AL contact of the inverter is closed, the closed contact of the ZJ relay and the BK contact of the interlock switch form a closed loop, and the standby pump switches on. The access method "quick break" light plate will not fall out of cards, to distinguish "quick break" current relay trip. Ruoyin inverter operating instructions, the frequency command input circuit break or control switch, potentiometer damage and make the inverter interrupt output, such fault inverter can not be identified. The solution is: choose a piece of input signal is DC0-1OV, corresponds to display 0 ~ 50 with switch output intelligent display instrument as a remote monitoring instrument (frequency table), normal operation as a frequency monitor. Using the switch (LW5-15 / B4815 / 5) contacts (11) - (12) of the original control motor as the input switch of the inverter operation command, the contacts (17) - (18), 20) concatenated with the lower limit alarm relay alarm ALM and thermal flashing alarm. When the inverter interrupts the output due to the above reasons, the alarm will sound and light when the frequency drops to 5Hz (settable). At the moment of closing, although the inverter frequency is lower than 5Hz, the lower limit alarm relay ALM of the frequency meter is closed, but the contacts (19) - (20) of the switch are not closed yet and the thermal flashing alarm will not send an alarm signal. If the original fault due to the inverter or motor failure of the original circuit breaker, zero sequence protection action, the protection of the export relay BCJ can also be self-spare pump. Light words still send a signal. So that the original circuit breaker relay protection and the newly installed inverter protection device integration. No matter what happens, can cast a backup pump or sound and light signals, so that energy-saving operation and safe operation of both correct.