Thermal Protection Reset; Thermal Protection Setpoints - GE MM300 Instruction Manual

PROTECTION ELEMENTS
Thermal protection
reset
NOTE:
NOTE
Thermal protection
setpoints
5–40
Operating at the thermal model protection limit is a serious event, and results in a lockout
that can not be reset until the motor has cooled, except with a level 2 or level 3 security
login. A setpoint is available (Minimize Reset Time - see section 6.3.1) that controls whether
lockout persists until the motor has cooled until the thermal capacity used reaches 15%
(approximately twice the cool time stopped setpoint), or until the relay estimates based on
learned thermal capacity used on start that the motor has cooled sufficiently for a
successful restart. For the latter, a 2% safety margin is included. While in lockout, the
motor can not be started via the MM300. Refer to section 6.4.2 - Thermal Start Inhibit, for
details.
If the motor is re-started it may re-trip quickly. Should process interruption concerns
outweigh the probable damage to the motor that early starting would incur, an external
circuit should be added that bypasses the relay to directly close the motor contactor.
A second setpoint controls whether once the motor has cooled as described above, the
lockout is replaced with a trip that can be manually reset without security login, or
alternatively the condition is fully reset allowing immediate restart.
When the "Reset Lockout Using Reset Key" setpoint is set to "Enabled," pressing the Reset
key resets all Lockout and Non-Lockout trips. When the GCP/BCP reset key is pressed
continuously for more than 12 seconds, the Thermal Capacity % will be reset to zero. By
default a 'Lockout Reset' also clears the Thermal Capacity % to zero. This feature can be
disabled by changing the setting "Reset TCU using Reset Key" to "Disabled".
Select the Home > Setpoints > Protection > Thermal page to edit the thermal protection
setpoints.
Figure 5-31: Thermal protection configuration setpoints
The following setpoints are available for thermal protection.
Standard Overload Curve
Range: 1 to 15 in steps of 1
Default: 4
This setpoint specifies the standard overload curve to the thermal characteristics of the
protected motor.
Overload Pickup Level
Range: 1.01 to 1.25 in steps of 0.01
Default: 1.01
This setpoint dictates where the overload curve begins as the motor enters an overload
condition. This is useful for service factor motors as it allows the pickup level to be
defined. The curve is effectively cut off at current values below this pickup.
MM300 MOTOR MANAGEMENT SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETPOINTS