Hitachi L300P - Manual (Page 177)

L300P Inverter
Oper
ati
ons
and Monitor
ing
4–47
Thermal Warning
Signal The purpose of the electronic thermal setting is to protect the motor from overloading,
overheating and being damaged. The setting is based on the rated motor current. The inverter
calculates the thermal rise (heating) of the motor using the current output to the motor squared,
integrated over the time spent at those levels. This feature allows the motor to draw excessive
current for relatively short periods of time, allowing time for cooling.
The Thermal Warning output [THM] turns ON to provide a warning before the inverter trips
for electronic thermal protection. You can set a unique thermal protection level for each of the
three motor profiles, as shown in the table below.
For example, suppose you have inverter model
L300P-110LFU2. The rated motor current is
44A. The setting range is (0.2 * 44) to (1.2 *44),
or 8.8A to 52.8A. For a setting of B012=44A
(current at 100%), the figure to the right shows
the curve.
The electronic thermal characteristic adjusts the
way the inverter calculates thermal heating,
based on the type of torque control the inverter
uses.
CAUTION: When the motor runs at lower
speeds, the cooling effect of the motor’s internal
fan decreases.
The table below shows the settings and their meanings. Use the one that matches your load.
Reduced Torque Characteristic – The left graph below shows the effect of the reduced torque
characteristic curve. For example, at 20Hz, the output current level to cause overheating in a
fixed time period is reduced by a factor of 0.8. The right graph below shows the reduced trip
current levels in those conditions for given trip times.
Function
Code
Function/Description Data or Range
B012 / B212 Electronic thermal setting (calculated
within the inverter from current output)
Range is 0.2 * rated current to
1.2 * rated current
Function Code Data Function/Description
B013 / B213
00 Reduced torque
01 Constant torque
02 Free-setting
Trip current at 60 Hz
Trip
time (s)
60
116%
0.5
0
51.0 52.8 66.0
120% 150%
A
Trip
time (s)
60
92.8%
0.5
0
40.8 42.2 52.8
96% 120%
A
Trip current
reduction
factor
x 1.0
x 0.6
0
5 20 60
Hz
x 0.8
Reduced trip current at 20 Hz