Eaton 66D2032G01, Руководство пользователя

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I.L. 17562
PR 0.3 Effective 8/99
transition on time (e.g. set P5L7 to TRN TIME and P5L6, TRNT=10 seconds) or current (e.g. set
P5L7 to TRN I and P5L5, TRNC to 130 % of FLA), among other options.
Figure 9.5 shows the impact of a stator RTD measurement. Look at the time period after
60 seconds (near the top). When RTDs report low stator temperature, the motor can run
continuously with current well above (to the right of) the UTC line. The lower the stator
temperature, the higher the acceptable sustained current moves beyond UTC - 200% of FLA in
the example. A hotter stator, perhaps caused by a high ambient temperature or a cooling
blockage, shifts the curve to the left and lowers the acceptable level of I
2
t. Be sure to set a
suitable RTD temperature trip value (WD T) according to 9.1.8 below; a setting of OFF causes
the relay to revert to the non-RTD algorithm even if RTDs are connected.
9.1.5 Load Shedding Function – In some applications, the MP-3000 can forestall a jam alarm
or trip, or a thermal trip, by sending a signal to the process to reduce loading. The load-shedding
function, if enabled, will close or open the AUX1 contact to shed process load when the motor
load current goes above the load-shed threshold LSPU, P9L1, for a time exceeding the load-
shed run delay LSDL, P9L3. This could, for example, be connected to stop flow of material into
the driven process until the load current drops below the load-shed dropout threshold LSDO,
P9L2 for time LSDL, P9L3.
Set the load-shed pickup current LSPU, P9L1 comfortably below the jam trip level. It may be
useful to set it below UTC, P1L4, particularly if RTDs are not used. See Section 5 explanation
for settings P9L1 to P9L3, and for imposed relationship rules on load shedding pickup, dropout,
and time delay settings.
9.1.6 Long Acceleration Time – The user can temporarily defeat the I
2
t thermal protection limit
after a start by setting a Long Acceleration Time delay (LAT, P5L10). This can be a dangerous
setting which blocks thermal tripping and holds the bucket at a 100% level if the load takes a
long time to reach running speed. An example is a motor spinning a large centrifuge. In using
LAT, the user is taking advantage of the partial cooling from airflow produced by motor spinning
at below-normal speed, as compared to unfanned heating of a locked rotor. The motor must be
rated for this severe starting duty. Also, the user must insure that the motor actually has begun
to spin well before the locked-rotor time has expired. This is accomplished by connecting a zero-
speed switch to Discrete Input 1 and setting P5L11 ZSW = ON. The zero-speed switch is a
contact that is closed when the motor is at rest, and opens as the motor begins to spin, usually at
5-10% of running speed. If ZSW is set to ON and the MP-3000 does not see the contact open in
½ the locked-rotor time setting, it trips the motor.
WARNING
Turn off LAT unless the application specifically demands it. Use a zero-speed switch with LAT.
Using an LAT setting greater than locked-rotor time without a zero-speed switch will temporarily
defeat thermal protection, and ruin the motor if the rotor actually is locked.
If LAT is used, check the settings of transition time TRNT, P5L6 and jam start delay JMSD, P3L7
to be sure they are coordinated with the prolonged starting cycle.
9.1.7 Using The Starting Current Profile Function – If the MP-3000 is communicating with a
Cutler-Hammer PowerNet host computer, the user can upload the actual time history of the
starting current from the moment of a particular start to a time well past the set locked-rotor time.
The actual current-versus-time profile can be visually checked against the cold-start protection
curve, which PowerNet plots for comparison. The PowerNet plot also includes the long-
acceleration extension of the thermal curve, and the jam trip limit. The profiled starting current is
the average rms phase current.