Basler BE1-CDS220, Инструкция по эксплуатации

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BE1-CDS220 Application 8-45
protection for high inertia motors. It is blocked when virtual control switch 243 is set to low inertia mode. If
high Inertia is selected, it is unblocked when starting as determined by intermediate logic VO7. Virtual
control switch 143 selects whether high inertia motor starting is determined by speed switch or by current
detection (50TP protection element set at 85% of locked rotor current).
In the MOTOR scheme, the 50TP protection element is used for motor start detection (50S). The 250TP
protection element is used to detect when the motor is running. It supervises the 150TP locked rotor
protection for low inertia motor applications and the 251P jam or stall protection. Targets should not be
enabled with the SG-TARG setting for either the 50TP or the 250TP function.
Integration of Protection, Control, and I/O Elements
The logic settings in Table 8-26 also include the logic equations that establish the control connections or
logic wiring between elements of the MOTOR scheme. For example, the two underlined equations in the
settings of Table 8-26 provide the electrical connection between the 87 element (trip enabled by the
settings) and trip output 1. Referring to Figures 8-14 and 8-15, all protection elements in the MOTOR
scheme are enabled to trip. All protection elements with the exception of 250TP start /run detection, are
connected to trip through output 1. Motor phase unbalance alarms are connected through output 5, and
motor overload alarms through output 4. Protection elements set at 0 are setting disabled and will not
provide a trip output even if logic enabled.
The 87, 50TN, 50TQ, 51P, and 251P protection elements provide primary and backup fault/open phase
protection, including stall protection for a running motor. The remainder of the protection is associated with
starting the motor. High and low inertia locked rotor protection is provided by 150TP and 151P protection
elements. Start/Run current detection for low inertia motors is provided by the 250TP protection element,
and start detection for high inertia motors is provided by either speed switch input or current detection
from the 50TP protection element.
High Inertia Motor Start
As shown on Figure 8-14, the first thing the user must do is select the high inertia position of virtual control
switch 243 and then select between motion detection by external speed switch or motion detection by
current sensing. This is accomplished by the position of virtual switch 143. If we assume current sensing
was selected, then, when the breaker is closed, 50TP picks up forcing VO7 high, and removing the block
from 151P locked rotor protection. Locked rotor 151P picks up and starts timing. If the motor current drops
below the 50TP setting before 151P times out, the locked rotor protection is blocked and the motor start
was successful. However, if the motor current stays high until 151P times out, the motor is tripped through
output 1 and the Major Alarm LED on the front panel lights.
If speed switch input is selected by the position of virtual switch 143, then, when the breaker is closed,
250TP picks up and a closed external speed sensing contact at input 2 unblocks the locked rotor
protection. If the speed sensing contact opens, or the 250TP drops out, locked rotor protection is blocked
and the motor successfully starts.
For high or low inertia starts, 251P jam or stall protection is blocked by V08 until 250T drops out or times
out.
For high inertia motors, the distance between the burn-up curve and the knee point of the start/run plot is
typically close. Locked rotor protection will reset when the motor comes up to speed, but abnormally high
run current could still be present, but not high enough to trip on overload. If the abnormal run current is
allowed to persist, motor life will be shortened through accelerated thermal aging. To alert the user to this
condition, when 250TP has timed out and 51P is picked up, virtual output 14 is programmed to go high
which drives alarm bit #22 in the programmable alarm mask and alarms through output 4 to the outside
world. It can also be masked to drive an alarm LED, and the alarm display to indicate when the overload
condition exists. If the overload is high enough to time out 51P, the breaker is tripped through output 1.
Phase imbalance can lead to stator and rotor overheating resulting in the same scenario as previously
discussed. For this reason, a circuit similar to the overload alarm is included for phase imbalance. When
51Q picks up, virtual output 15 is programmed to go high which drives alarm bit #23 in the programmable
alarm mask and alarms through output 5 to the outside world. It can also be masked to drive an alarm
LED, and the alarm display to indicate when the imbalance condition exists. If the imbalance is high
enough to time out 51Q, the breaker is tripped through output 1.