Section 6
1MAC050144-MB C
Supervision functions
466
615 series ANSI
Technical Manual
Figure 248:
Time delay for cumulative start
This module also protects the motor from consecutive startups. 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
startup time counter is set to
Cumulative time Lim
- 60s x
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 startups occurred,
START_CNT
. The value
can be reset from the clear menu.
The calculated values of
T_RST_ENA
,
T_ST_CNT
and
START_CNT
are available
through the monitored data view.
The
BLK_LK_ST
input signal is used to block the operation of the
LOCK_START
output.
The activation of the
BLOCK
input resets the complete operation of the cumulative startup
counter module.
6.6.5
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 or mechanical
constraint, this starting method is not suitable. The full voltage starting produces the
highest starting torque. A high starting torque is generally required to start a high-inertia
load to limit the acceleration time. In this method, full voltage is applied to the motor when
the switch is in the "On" position. This method of starting results in a large initial current
surge, which is typically four to eight times that of the full-load current drawn by the
Содержание 615 Series ANSI
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Страница 29: ...1MAC050144 MB C Section 615 series ANSI 22 Technical Manual ...
Страница 389: ...Section 4 1MAC050144 MB C Protection functions 382 615 series ANSI Technical Manual ...
Страница 485: ...Section 6 1MAC050144 MB C Supervision functions 478 615 series ANSI Technical Manual ...
Страница 635: ...Section 10 1MAC050144 MB C Other functions 628 615 series ANSI Technical Manual ...
Страница 707: ...Section 15 1MAC050144 MB C Applicable standards and regulations 700 615 series ANSI Technical Manual ...
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