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.
WARNING! Some motors have low speed characteristics which
cause overheating and winding failure under light load or no load
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
2
t Overload
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
60
Motor Speed (%)
TEFC and Open Ventilated
50
30
40
10
0
20
Motors
M
ax
im
um
A
llo
w
ed
M
ot
or
T
or
qu
e
(%
)
40
20
60
0
and TENV
Inverter Duty
100
80
100
90
70
80
Motors
Fan Cooled
FIGURE 39 – MAXIMUM ALLOWED MOTOR TORQUE vs. SPEED
Open Ventilated Motor
(100 CFM Min.)
Fan or Blower
Airflow
FIGURE 40 – OPEN VENTILATED MOTOR WITH EXTERNAL COOLING
Summary of Contents for SERIES 5
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