Cumulative time Lim
. The start time counter reduces at the rate of the value of
Counter Red rate
.
The LOCK_START output becomes activated at the start of MOT_START. The output
remains active for a period of
Restart inhibit time
.
Figure 617: Time delay for cumulative start
This module also protects the motor from consecutive start-ups. When the
LOCK_START output is active, T_RST_ENA shows the possible time for next restart.
The value of T_RST_ENA is calculated by the difference of
Restart inhibit time
and
the elapsed time from the instant LOCK_START is enabled.
When the ST_EMERG_ENA emergency start is set high, the value of the cumulative
start-up time counter is set to
Cumulative time Lim
- 60s ·
Emg start Red rate
. This
disables LOCK_START and in turn makes the restart of the motor possible.
This module also calculates the total number of start-ups occurred, START_CNT. The
value can be reset from the Clear menu.
The old
Number of motor start-ups occurred
counter value ( START_CNT) can be
taken into use by writing the value to the
Ini start up counter
parameter and
resetting the value via the Clear menu from WHMI or LHMI.
The calculated values of T_RST_ENA, T_ST_CNT and START_CNT are available in the
Monitored data view.
The activation of the BLK_LK_ST input signal deactivates the LOCK_START output.
The activation of the BLOCK input signal resets the cumulative start-up counter
module.
4.10.6 Application
When a motor is started, it draws a current well in excess of the motor's full-load
rating throughout the period it takes for the motor to run up to the rated speed.
The motor starting current decreases as the motor speed increases and the value of
current remains close to the rotor-locked value for most of the acceleration period.
The full-voltage starting or the direct-on-line starting method is used out of the
many methods used for starting the induction motor. If there is either an electrical
1MRS759142 F
Protection functions
REX640
Technical Manual
1099
To Next Page
Loading...
