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8
DRIVE OPERATION
8.1 Important Application Information
1. Motor with External Fan Cooling: Most totally enclosed fan-cooled (TEFC) and
open ventilated 3-phase AC induction motors will overheat if used beyond a limited
speed range at full torque. Therefore, it is necessary to reduce motor load as speed
is decreased.
Note: Some fan-cooled motors can be used over a wider speed range. Consult the
motor manufacturer for details.
conditions. If the motor is operated in this manner for an extended period of
time, it is recommended that the unloaded motor current be checked from 2 –
15 Hz (60 – 450 RPM) to ensure motor current does not exceed the nameplate
rating. Do not use motor if the motor current exceeds the nameplate rating.
It is recommended that the drive be used with Inverter Duty or TENV motors.
Inverter duty and most
totally enclosed non-ven-
tilated (TENV) motors can
provide full rated torque
over an extended speed
range without overheat-
ing. See Figure 39.
If external fan cooling is
provided, open ventilated
motors can also achieve
an extended speed range
at full rated torque. A box
fan or blower with a mini-
mum of 100 CFM per HP
is recommended. Mount
the fan or blower so the
motor is surrounded by
the airflow. See Figure 40.
2. Electronic Motor
Overload Protection:
The drive contains
Modified I
Protection. A Current
Limit (CL) circuit limits the
drive current to a
factory preset level of 160% of the rated drive current. The CL Trimpot is used to
recalibrate the drive current from 60% thru 200%. The Power Start™ circuit provides
an overshoot function that allows most motors to develop more than 200% of start-
ing torque and breakdown torque.
26
WARNING! Some motors have low speed characteristics which
cause overheating and winding failure under light load or no load
2
t Overload
FIGURE 39 – MAXIMUM ALLOWED MOTOR TORQUE vs. SPEED
100
Inverter Duty
80
and TENV
Motors
60
40
20
0
0
10
20
FIGURE 40 – OPEN VENTILATED MOTOR WITH EXTERNAL COOLING
Open Ventilated Motor
Fan Cooled
TEFC and Open Ventilated
Motors
30
40
50
60
70
Motor Speed (%)
Airflow
80
90
100
Fan or Blower
(100 CFM Min.)
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