GE Industrial Solutions AF-650 GP MultiPulse Drive Panel User Manual
Page 15
MULTIPULSE DRIVE PANEL
15 GE Energy ©2012 GE Company All Rights Reserved
Motors with Service Factor of 1.15 or
Greater - adjust OL relay dial to the
motor nameplate FLA.
Motors with Service Factor Less than
1.15 - adjust OL relay dial according to
the formula FLA times Service Factor
times 0.90.
Example: 30 A motor with 1.00 service factor
Set OL dial at 30 x 0.90 = 27.0 A
If the overload relay dial is set correctly but
trips in normal running situations, then your
motor is probably undersized for your load.
Possible corrective actions are:
1. Make sure there is not an unintended
additional loading on the motor resulting
in the excessive current.
2. Try another OL relay. Perhaps the
tolerances on the one included with your
panel are unfavorable.
3. Reduce the load on the motor. For
variable torque loads when running on the
drive, this can be accomplished simply by
slowly reducing speed until the tripping
stops. For bypass operation this would
require a change to the driven load.
If the overload relay dial is set correctly but
tripping occurs on across-the-line starts this is
probably due to a large load inertia which
results in high starting current being applied
for a longer time to accelerate the motor from
a stopped to full speed condition. Traditionally
the problem of starting motors with high
inertia loads across the line has been solved
by a number of methods falling into the
category of soft-starters. The AF-600 FP and
AF-650 GP adjustable frequency drive is, by its
very nature, a “soft-starter” since it applies a
very low voltage to the motor when it is
stopped and gradually increases to full
voltage at full speed. Recognizing that this
problem can only occur during full voltage
across-the-line starts (in other words, starting
in bypass mode), then possible corrective
actions are:
1. Allow the OL to cool sufficiently between
restarts. There is typically a 4 to 1
difference between the operation times of
the OL in their cold state versus their
warm state.
2. Try another OL relay of the same rating.
Tolerances on the OLs are loose, trip times
can vary significantly from unit to unit of
the same rating (range of 2 to 1 or more is
not uncommon).
3. Reduce the load on the motor during
acceleration. Total motor load during this
period is the sum of the accelerating
torque plus load torque. Once motor is up
to speed the load can be reapplied.
Analog output
CAUTION: For all panels the overload relay
dial should never be set higher than the
panel rated current even if allowed by the
above formula because the overload relay
protects panel components such as the
contactors and line reactor in addition to the
motor.
WARNING: The overload relay should not be
turned to a higher setting than allowed by the
rules above to allow starting the motor across
the line without tripping. Doing so will
compromise the overload protection which
could lead to component damage or fire which
could threaten personnel safety. Refer to NEC
for further information.