Lenze SCD Series - Manual (Page 44)

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When using a 0-10 VDC or 4-20 mA analog speed reference signal, this parameter also sets the drive
speed that corresponds to the maximum analog input (10 VDC or 20 mA).
NOTE 1: On drives equipped with the High Output Frequency option, this parameter can be set up
to 999.9 Hz.
NOTE 2: If this parameter is changed while the drive is running, the new value will not take effect
until the drive is stopped.
P25 CURRENT LIMIT
This sets the maximum allowable output current of the drive. The maximum setting is either 180% or
150%, depending on whether LINE VOLTAGE SELECTION (Parameter 01) is set to HIGH or LOW.
The drive will enter current limit when the load demands more current than the CURRENT LIMIT
setting. When this happens, the drive will reduce the output frequency in an attempt to reduce the
output current. When the overload condition passes, the drive will accelerate the motor back up to
the speed setpoint.
P26 MOTOR OVERLOAD
The SCD Series is UL approved for solid state motor overload protection, and therefore does not
require a separate thermal overload relay for single motor applications.
The drive contains an adjustable thermal overload circuit that protects the motor from excessive
overcurrent. 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
current rating in order to properly protect the motor. See the example below.
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 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 460 Vac, 60 Hz motor requires a V/Hz ratio of 7.67 (460 V / 60 Hz = 7.67 V/Hz) to
produce full torque. Setting the BASE FREQUENCY to 60 Hz causes the drive to output full voltage
(460 Vac) at 60 Hz, which yields the required 7.67 V/Hz. Output voltage is proportional to output
frequency, so the 7.67 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.