Multilin 469 Motor Management Relay ... - GE Digital Energy

CHAPTER 5: SETTINGS
5.8.3 Jogging Block
phase current rises from 0 to greater than overload pickup and then, after acceleration,
falls below the overload curve pickup level. If the Start Inhibit feature is enabled, the
amount of thermal capacity available (100% – THERMAL CAPACITY USED) is compared to
the LEARNED STARTING CAPACITY each time the motor is stopped. If the thermal capacity
available does not exceed the LEARNED STARTING CAPACITY, or is not equal to 100%, the
Start Inhibit Block is activated until there is sufficient thermal capacity. When a block
occurs, the lockout time will be equal to the time required for the motor to cool to an
acceptable start temperature. This time is a function of the S5 THERMAL MODEL
THERMAL MODEL COOL TIME CONSTANT STOPPED settings.
If this feature is turned “Off”, the THERMAL CAPACITY USED must reduce to 15% before an
overload lockout resets. This feature should be turned off if the load varies for different
starts.
For example, if the THERMAL CAPACITY USED for the last 5 starts is 24, 23, 27, 25, and 21%
respectively, the LEARNED STARTING CAPACITY is 27% × 1.25 = 33.75% used. If the motor
stops with 90% thermal capacity used, a start block will be issued. When the motor has
cooled and the level of thermal capacity used has fallen to 66%, a start will be permitted. If
the COOL TIME CONSTANT STOPPED settings is programmed for 30 minutes, the lockout
time will be equal to:
TCused TCused_start e t – τ ⁄
= × 66% 90% e t – 30 ⁄
= ×
66
t = ln----- × – 30 = 9.3 minutes
90
PATH: SETTINGS S7 MOTOR STARTING JOGGING BLOCK
JOGGING [
MESSAGE
MESSAGE
JOGGING BLOCK:
Off
MAX. STARTS/HOUR
PERMISSIBLE: 3
TIME BETWEEN
STARTS
Range: On, Off
Range: 1 to 5 in steps of 1
The Jogging Block feature may be used to prevent operators from jogging the motor
(multiple starts and stops performed in rapid succession). It consists of two distinct
elements: Starts/Hour and Time Between Starts.
(EQ 5.11)
Range: 0 to 500 min. in steps of 1
The Starts/Hour feature does not guarantee that a certain number of starts or start
attempts will be allowed within an hour; rather, it ensures that a certain number of start
attempts will not be exceeded within an hour. Similarly, the Time Between Starts feature
does not guarantee another start will be permitted if the TIME BETWEEN STARTS
PERMISSIBLE elapses after the most recent start. Rather, it ensures a minimum time
between starts. If however, the first start attempt from cold is unsuccessful due to a jam or
it takes long because the process is overloaded, the Thermal Model might reduce the
number of starts that can be attempted within an hour. It may also cause a lockout time
that exceeds a Time Between Starts lockout that may have been active. Such a thermal
lockout will remain until the motor has cooled to an acceptable temperature for a start.
469 MOTOR MANAGEMENT RELAY – INSTRUCTION MANUAL 5–67