Introduction
In the bag filter project has 8 50kW to enter the branch
to pump, 4 30kW reflux pump uses the Fuji frequency changer velocity
modulation, the bag filter entire work process controls the room by
the host the FOXBORO collection systems control. Feed pump
frequency conversion velocity modulation movement to split-ring
condition, through DCS collection system hypothesis frequency value
control current capacity; Reflux pump frequency conversion
velocity modulation movement to closed loop condition, control
backflow tank liquor position. In the test run process, the feed
pump, the reflux pump frequency changer trips one after another, on
the frequency changer display monitor demonstrated "OU2 decelerates
when 过电?. The feed pump trips the reason is because the
bag filter craft reason creates the feed pump load suddenly to reduce;
The reflux pump when 2-3 bag filter to filters the cloth
counter- flushing, circulation 卸料, time short, the current
capacity is big, in the branch thick liquid mixes has the air, causes
the reflux pump idle operation, the load suddenly reduces, causes the
electrical machinery to be in 再生制动 the operating mode, causes
the frequency changer middle direct current return route 过电?
the frequency changer protection trips. Although has taken some
measures in the test run stage, but the breakdown hidden danger
eliminates by no means, needs to consider uses the cost to be lower,
the structure simple resistance braking unit.
In deals with this issue in the process, is altogether used many
frequency changers the identical direct current generatrix to solve
this question enlightenment, we to the feed pump, the reflux pump from
the craft, on the frequency conversion velocity modulation system have
carried on some modification, better solution frequency conversion
velocity modulation system middle direct current 过电?question.
1 pair of reflux pump system processing
(1) the reflux pump was because in the material thick
liquid mixes in the air 打空?to initiate the breakdown, in the
electrical system aspect mainly was because the reflux pump was at the
closed loop running status to create, changed the reflux pump
frequency changer by the closed loop running status the split-ring
movement way then to be possible to solve this breakdown. Namely
controls the room in the host on the FOXBORO collection system to
return to the launder to establish Gao Kewei, to compare Gao Kewei,
the lower material position, the low material position 4 materials
positions parameter, causes the reflux pump when the lower material
position the low speed movement, compares when Gao Liaowei the high
speed movement, the frequency changer adds, decelerates time item to
lengthen is 60s, causes the reflux pump frequency conversion velocity
modulation system not to expect the thick liquid current capacity the
instantaneous change to change.
(2) in the craft aspect, to returns to the launder place in each
bag filter backflow exportation to add the cushion trough, the change
backflow current capacity sudden change condition, reduces the current
capacity change to the frequency changer the influence.
Processes after above, the reflux pump has been able stably to
move, thorough settlement middle direct current return route 过电?question. 2 pair of feed pumps systems processing original
system 8 bag filters divide into 2 groups, 4 feed pumps and 2 reflux
pumps are a group, the normal time each group has 2-3 to enter the
branch to pump in moves with 1 reflux pump, each group has 1 reflux
pump to do spare, each group of 6 equipment coexist in section of
exchanges generatrixes. Because each group has 1 reflux pump
long-term movement, after therefore passes through the above
processing to move very stably. We use the reflux pump frequency
conversion system for to enter the branch to pump the frequency
conversion system 再生制动 time the energy which produce in the
middle direct current return route to provide 泄放 the circuit.
(]) 4 feed pumps and 2 reflux pumps frequency changers power
source side alternating voltage all is 380V, the middle DC voltage is
about 310V, basic is mutually same, can have the load and the
frequency control influence the undulation. If each frequency
changer middle direct current return route directly connects, after
the middle direct current return route system allows the quantitative
change to be big can bring many advantage, for example: The
middle DC voltage is relatively constant, after the electric capacity
parallel stored energy capacity enlarges; Enhances the system
the power factor and the system uses electricity the efficiency,
reduces the electrical network the harmonic current; Between
various frequency changers the capacity may supplementary,
再生制动 the condition produces the unnecessary energy may by
other frequency changer absorptions, the transformation, when the
normal operation cannot create the frequency changer middle direct
current return route 过电?to trip, optimized system dynamic
characteristic and so on. But because the frequency changer
power source side has used not the controllable rectification bridge,
has flowed the rectification bridge electric current not not
controllably, even can surpass the electric current which its can
withstand to damage: Directly altogether uses the middle direct
current return route, short-circuits the breakdown when the phylogeny,
because the rectification bridge partial protections less also the
sensitivity is bad, each frequency changer cannot promptly excise, can
cause the breakdown further to expand, causes a bigger losses.
Therefore directly connects time the middle direct current
return route, the frequency conversion velocity modulation system can
change is unreliable. Electric circuit uses the diode, the
contact device main goal in chart in 1 is for prevent the frequency
conversion system because altogether to use the direct current
generatrix to initiate the breakdown, achieved both has been able to
eliminate the breakdown, and did not reduce the frequency changer
reliable goal.
(2) feed pump frequency changer return route diode 管主 if
causes between each feed pump frequency changer to be mutually
independent in the movement, mutually does not affect, 再生制动
the condition produces energy by noramal work reflux pump consumption,
realization energy full use.
The contact device uses for to realize the frequency changer
with altogether to use the direct current generatrix, mutually
connects, the power failure and the overhaul when the frequency
changer movement mutually isolates; When breaks down the prompt
excision with altogether uses the direct current generatrix the
relation.
(3) 2 reflux pumps in
Often moves when for as soon as uses as soon as to
prepare, in order to prevent also moves in the peculiar circumstance
next 2 reflux pumps, with altogether used the direct current
generatrix in 2 reflux pumps frequency changers middle direct current
return route to increase the diode, enabled 2 reflux pumps mutually to
isolate, reduces the breakdown.
(4) in normal condition feed pump frequency conversion velocity
modulation system to backflow frequency changer middle direct current
return route feed, because enters the branch to pump the frequency
changer to be bigger than the reflux pump, also has the certain
remainder, when normal operation cannot create the harm to the feed
pump frequency changer, only has in the reflux pump rectification
bridge shuts or altogether uses in the situation which the direct
current generatrix occurs short-circuits, only then can have the fault
current inflow middle direct current generatrix, in this kind of
situation, this return route mainly depends upon frequency changer
itself each kind of protection namely using frequency changer
breakdown signal 3 0C, 30B causes the contact device
movement which increases in each frequency changer return route,
promptly with altogether uses the frequency changer the generatrix to
excise, Avoids breaking down bigger.
(5) in the return route increases the diode selects ordinary
rectification diode ZP20, the passing condition mean current is 20A,
can withstand the surge current may reach 150-200A, each frequency
changer middle DC voltage basically about 310V, 再生制动 the
condition produces too much the electric current although peak-to-peak
value big somewhat, but time short, the diode withstands the electric
current with directly meets in the middle direct current generatrix
beginnings and ends resistance braking unit is different, selects the
ZP20 diode to add the radiator to be able to satisfy the electric
circuit request.
(6) because increases the contact device must shut off under the
malfunction altogether uses the big electric current which between the
direct current generatrix and the frequency changer possibly has, 1 ~
6KM selects the CJ-50 exchange contact device.
(7) in order to prevent the reflux pump frequency changer middle
direct current return route in pours into when the big electric
current which possibly has 过电?trips, adopts: (1)
Controls the room while the host on the FOXBORO collection
system to take the measure to prevent each group of movements 2-3 bag
filter instead; Center washes unloads the branch, causes each
bag filter 卸料 instead; Center washes the time is separated
by 3-5min. (2) In altogether uses in the direct current
generatrix installs 1 group of resistance braking unit, maximum limit
reduces the reflux pump frequency changer middle direct current return
route 过电?probability, safeguards the bag filter frequency
conversion system movement the security.
(8) when construction had considered the middle direct current
return route possibly short-circuits the situation, selects the high
quality insulation cab-tire cable to make the ties, strengthened the
insulation in the part, reduced the probability which the middle
direct current return route earth short-circuits.
(9) frequency changer movement environment better, 10 frequency
changers have the special-purpose frequency changer room, in the room
install 2 cabinets types air conditioning, clean is neat, is
advantageous to the frequency changer radiation and the reduced
frequency changer breakdown probability.
3 concluding remark
This electric circuit after the actual movement, the
effect is better. This improvement program has realized the bag
filter frequency conversion system stable movement with less ordinary
parts, has omitted the multi- wraps resistance braking unit, enable
the electrical machinery 再生制动 energy to obtain the full use,
was processes the frequency changer 再生制动 energy and the
breakdown effective way.
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