KB Electronics KBVF-48 - Manual (Page 13)

4 IMPORTANT APPLICATION INFORMATION
4.1 MOTOR WITH EXTERNAL FAN
COOLING – Most totally enclosed fan-
cooled (TEFC) and open ventilated 3-
phase AC induction motors will over-
heat if used beyond a limited speed
range at full torque. Therefore, it is nec-
essary 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 cur-
rent 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-ventilated (TENV)
motors can provide full rated
torque over an extended speed
range without overheating. See
Figure 6.
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 minimum of 100
CFM per HP is recommended.
Mount the fan or blower so the
motor is surrounded by the air-
flow. See Figure 7.
4.2 ELECTRONIC MOTOR
OVERLOAD PROTECTION –
The drive contains Modified I 2 t
Overload Protection.* Part of this
function consists of a Current
Limit (CL) circuit, which limits the
drive current to a factory preset
13
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 6 – MAXIMUM ALLOWED MOTOR TORQUE vs. SPEED
Selectable Jumpers
A/
M
CO
N2
CO
N1
J2
50
/6
0H
z
CO
N3
J1
X2
X1
P1
F
- S
-
R
PWR
P3
P2
ST
Diagnostic LEDs
Main Speed Potentiometer
and Signal Input Terminals
M
IN
CL
M
AX
AC
C
DE
C/
B
CO
M
P
Adjustable Trimpots
FIGURE 5 – EXPANDED VIEW OF JUMPERS AND TRIMPOTS
Open Ventilated Motor
(100 CFM Min.)
Fan or Blower
Airflow
FIGURE 7 – OPEN VENTILATED MOTOR WITH EXTERNAL COOLING