GE Multilin 469, Instruction Manual

Page: 209 / 338

CHAPTER 5: SETTINGS
469 MOTOR MANAGEMENT RELAY – INSTRUCTION MANUAL 5–67
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
Ö
THERMAL MODEL
ÖØ
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:
(EQ 5.11)
5.8.3 Jogging Block
PATH: SETTINGS
ZV
S7 MOTOR STARTING
ZV
JOGGING BLOCK
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.
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.
TC
used
TC
used_start
e
t
–
τ ⁄
×
=
66% 90% e
t
–
30 ⁄
×
=
⇒
t
66
90
------ ln 30
–
×
=
⇒
9.3 minutes
=
„
JOGGING [
JOGGING BLOCK:
Off
Range: On, Off
MESSAGE
MAX. STARTS/HOUR
PERMISSIBLE: 3
Range: 1 to 5 in steps of 1
MESSAGE
TIME BETWEEN
STARTS
Range: 0 to 500 min. in steps of 1