LEESON SM-Basic Series Sub-Micro Inverters (Obsolete) - Manual (Page 35)

31
When using a speed pot reference, this parameter also sets the drive speed that corresponds to the
maximum analog input (10 VDC).
NOTE: If this parameter is changed while the drive is running, the new value will not take effect
until the drive is stopped.
25 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.
If the load demands more current than the CURRENT LIMIT setting, the drive will reduce the output
frequency in an attempt to reduce the output current. When the overcurrent condition passes, the
drive will accelerate the motor back up to the speed setpoint.
To set this parameter, divide the desired setting by 10 and enter that value. For example, if the
desired setting is 150%, set this parameter to 15.
26 MOTOR OVERLOAD
The SM-Basic 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").
To set this parameter, subtract 1 from the desired setting and enter that value. For example, if the
desired setting is 75%, set this parameter to 74. 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.
Example: A 2 HP, 230 Vac drive with a 6.8 Amp rating is operating a 1 HP motor with a current
rating of 4.0 Amps. Dividing the motor current rating by the drive current rating yields 59% (4.0 /
6.8 = 0.59 = 59%), so this parameter should be set to 58 (58 + 1 = 59%).
27 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 about 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.