Emb Overload; Sample Overload Device - Danfoss VLT Option Panel Instruction Manual

EMB Overload

General Information
The overload device provides overcurrent
protection for the motor when running in
bypass. The thermally activated overload
monitors motor current and trips to remove
power to the motor if a sustained overcurrent
condition exists. A Class 20 overload is
standard with a variable setting for motor
current. Test and reset buttons are also
provided. In drive mode, the drive provides
current sensing and trip protection. Fuses
provide quick action for high over current
conditions.
Prior to Enabling Overload
• Verify that the overload current dial
setting matches the motor FLA rating
on the motor nameplate.
• If the motor FLA is greater or less than
range of the current dial, reconfirm that
the motor hp and voltage are within
the option panel (and drive) rating. If
less than the FLA rating, replace the
overload with the correct size. If
greater than the FLA rating, replace
the panel with one of a proper rating.
CAUTION
M D !
OTOR AMAGE
R
EPEATED ATTEMPTS TO RESET OVERLOAD CAN CAUSE MOTOR
. C
DAMAGE ORRECT OVERLOAD CONDITION AND LET OVERLOAD
AND MOTOR RETURN TO NORMAL OPERATING TEMPERATURE BEFORE
. S
RESETTING EE MOTOR MANUFACTURER
TIME BETWEEN START ATTEMPTS
CONDITION AND LET MOTOR RETURN TO NORMAL OPERATING
TEMPERATURE COULD CAUSE MOTOR DAMAGE
Operation
Overloads are rated by class. The class is
defined by the NEC to determine the maxi-
mum time to trip. A Class 20 overload, for
example, has a typical trip delay of 20 sec-
onds or less at 600% current and normal
operating temperature. This allows for high
32
'
S RECOMMENDATIONS FOR
. F
AILURE TO CORRECT OVERLOAD
.
motor inrush current for 20 seconds while the
motor is ramping up to synchronous speed.
The trip time, however, is based on the
percentage of overload. The higher the
overload, the shorter the trip time. It is impor-
tant that the overload class not exceed the
motor class rating or motor damage could
occur. For dual motor operation, an overload
is provided for each motor. For contact motor
select, one overload is provided and moni-
tors either motor when selected.
Overload Function Setup
• Set the overload current dial to the
FLA of the motor. DO NOT add the
service factor of the motor into the
setting. A service factor of 120% for
Class 20 is designed into the over-
load.
• Pressing the test pushbutton verifies
the operation of the overload. The
overload should trip when pressed.
Use the reset pushbutton to reset the
overload after test.
• Reset is used to reset the overload
after it trips. If the overload is still hot,
wait until the motor reaches normal
operating temperature before reset-
ting. The overload offers a manual
(hand) or auto reset selection. It is
highly recommended to operate in the
manual factory setting to prevent the
risk of damage to the motor.
Class 20
TEST
98NO
97NO
T2
T1
Figure 5-5. Sample Overload Device
TRIP
MANUAL
AUTO
RESET
95NC
96NC
T3