1st, electric current protection function
In the frequency changer, crossed the electric current
protection the object mainly to refer has 突变?the archery
target, the electric current peak value surpasses the frequency
changer to allow the value the situation
Because the contravariant component overload capacity is worse,
therefore the frequency changer the electric current protection is a
very important link, until now, has developed extremely consummates
(1) electric current reason
1st, in the work the electric current namely has driven the system to appear the electric
current in the work process Its reason approximately comes from
following several aspects:
(1) electric motor meets the shock load, or the
transmission system appearance "catches" the phenomenon, causes the
electric motor electric current suddenly increase
(2) frequency changer output side short-circuits,
like occurs the out-port to electric motor between ties mutually
short-circuits, or the electric motor interior occurs short-circuits
and so on
(3) frequency changer own work is not normal, if in
the contravariant bridge the identical 桥臂 two contravariant
component appears in unceasingly in turn work process exceptionally.
For example as a result of the environment hyperpyrexia, or
contravariant component itself gets older and so on the reason, causes
the contravariant component the parameter to change, causes in turn
the process, a component already led passes, but another component
actually also not with enough time shuts off, causes identical 桥臂
on, the next two components "goes nonstop to", caused the DC voltage,
between the cathode to be at short-circuits the condition.
2nd, 升 when the electric current has
worked as load inertia bigger, but 升 the time establishes too
short-time, meant in 升 process, frequency changer working
efficiency rise too quick, electric motor synchronized rotational
speed rapid rise, but the electric motor rotor rotational speed
comparatively greatly cannot follow because of the load inertia, the
result is 升 the electric current too is big.
3rd, 降 the center the electric current has worked as the load the inertia is bigger, but 降
the time establishes too short-time, also can cause the electric
current. Because, 降 time too short, synchronized rotational
speed rapid drop, but the electric motor rotor because the load
inertia is big, still maintained a higher rotational speed, by now
similarly could be the rotor winding cuts the magnetic line of force
the speed too greatly to produce the electric current.
(2) processing method
1st, when starting one 升 trips, this
is the electric current extremely serious phenomenon, main inspection
Does (1) work machinery have catches
Does (2) load side have short-circuits, has
with the megameter inspection to the place short-circuits
Does (3) frequency changer power module
have the damage
(4) electric motor starting moment
excessively is small, drives the system not to be able to transfer
2nd, when starting trips not immediately,
but trips in the movement process, main inspection
(1) 升 time hypothesis too is short,
lengthens the rise time
(2) decelerates the time hypothesis too to
be short, lengthens decelerates the time
(3) torque compensates (U/F compared to) to
establish too in a big way, causes the low frequency time idling
electric current oversized
(4) electronic thermal relay 整定 is
improper, the working current establishes too slightly, causes the
frequency changer misoperation
These are we works the time experience, hoped we the
electrician in usually reads, the theory knowledge adds on the
practice work diligently, then we certainly can complete each matter!
Wishes you to work happily!
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