LEESON SM Series Sub-Micro Inverters - Manual (Page 42)

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P26 MOTOR OVERLOAD
The SCL/SCM Series is UL approved for solid state motor overload protection, and therefore does not
require a separate thermal overload relay for single motor applications. This circuit allows the drive to
deliver up to 150% current for one minute. If the overload circuit “times out”, the drive will trip into an
OVERLOAD fault (displayed as “PF”). MOTOR OVERLOAD should be set to the ratio (in percent)
of the motor current rating to the drive’s output current rating to properly protect the motor.
Example: A 3 HP, 480 Vac drive with a 4.8 Amp rating is operating a 2 HP motor with a current rating
of 3.4 Amps. Dividing the motor current rating by the drive’s output current rating yields 71% (3.4 / 4.8
= 0.71 = 71%), so this parameter should be set to 71%.
P27 BASE FREQUENCY
The BASE FREQUENCY determines the V/Hz ratio by setting the output frequency at which the drive
will output full voltage to the motor. In most cases, the BASE FREQUENCY should be set to match the
motor’s rated frequency.
Example: A 230 Vac, 60 Hz motor requires a V/Hz ratio of 3.83 (230 V / 60 Hz = 3.83 V/Hz) to
produce full torque. Setting the BASE FREQUENCY to 60 Hz causes the drive to output full voltage
(230 Vac) at 60 Hz, which yields the required 3.83 V/Hz. Output voltage is proportional to output
frequency, so the 3.83 V/Hz ratio is maintained from 0 - 60 Hz, allowing the motor to produce full
torque from 2 Hz (below 2 Hz there is less torque due to slip) up to 60 Hz.
NOTE: If this parameter is changed while the drive is running, the new value will not take effect
until the drive is stopped.
P28 FIXED BOOST
FIXED BOOST increases starting torque by increasing the output voltage when operating below half of
the base frequency. For better out-of-the-box performance, SCL/SCM Series drives are shipped with a
setting that is different from the factory default of 1%. Units rated 0.33 to 1 HP (0.25 to 0.75 kW) =
5.3%, 1.5 to 2 HP (1.1 to 1.5 kW) = 4.4%, 3 HP (2.2kW) = 3.6%, 5 HP (4.0 kW) = 3.0%, 7.5 HP
(5.5 kW) = 2.7%, 10 HP (7.5 kW) = 2.4%, and 15 HP (11 kW) = 2.2%.
P29 ACCELERATION BOOST
ACCELERATION BOOST helps accelerate high-inertia loads. During acceleration, the output voltage
is increased to increase motor torque. Once the motor reaches the new speed setpoint, the boost is turned
off and the output voltage returns to the normal value.