Specifications

18
FIGURE 7 – MAXIMUM ALLOWED MOTOR TORQUE
VS.
SPEED
MOTOR SPEED (%)
INVERTER DUTY
AND TENV MOTORS
0 10 20 30 40 50 60 70 80 90 100
MAXIMUM
ALLOWED
MOTOR
TORQUE %
100
80
60
40
20
0
FAN COOLED TEFC AND
OPEN VENTILATED MOTORS
FIGURE 8 - OPEN VENTILATED MOTOR
WITH EXTERNAL FAN COOLING
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
airflow. See Figure 8.
5.2 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 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 starting torque.
Standard I
2
t is undesirable because it causes nuisance tripping. It allows a very high
motor current to develop and will turn the drive off after a short period of time. The RMS
Current Limit Circuit avoids this nuisance tripping while providing maximum motor
protection.
If the motor is overloaded to 120% of full load (75% of the CL setting), the I
2
t Timer starts.
If the motor continues to be overloaded at the 120% level, the timer will shut down the
drive after 30 minutes. If the motor is overloaded to 160% of full load, the drive will trip in
6 seconds. See Section 7.6, on page 23.
*UL approved as an overload protector for motors.