Hitachi SJ Series User Manual page 201

Chapter 12
Change of electronic thermal characteristics
Ｑ
• Want to make protection taking account of the
cooling function at a low speed.
• Want to change the thermal protection setting
pattern freely.
Ａ
• Optimal protection characteristics can be achieved
with the deterioration of the cooling ability of the
motor at a low speed taken account of.
([bC111]=00)
• Frequency-dependent characteristics can be set in
the selection of the electronic thermal
characteristics. ([bC111]=02)
Parameters
Item Parameters
First electronic
thermal
characteristics
selection
Reduced torque electronic thermal [bC111]=00
(Ex. 2) Induction motor rated current 64A,
[bC110]=64 (A)
For base frequency [Hb104]=60Hz,
output frequency=20 Hz
Reduction ratio
X1.0
X0.8
X0.6
0 5 16
0
6 20
Trip time (s)
×1
×0.8
60
3.0
55.8
(87.2%) (120%)
Data
[bC111]
Output frequency
(Hz)
50
60
Base frequency
Output current (A)
76.8 102.4
(Ratio to ND rated
(160%)
current)
！
• Autocooling motor needs to be used with reduced
load (current) since the cooling function of the
autocooling fan becomes less effective when the
motor rotation frequency decreases.
• The reduced torque characteristics are in
accordance with the heat generation of the
autocooling motor.
Reduced torque characteristics:
00 Pattern for cooling function deterioration at a
low speed
Constant torque characteristics:
01
Pattern for constant output
Free setting:
02 Multiple patterns are available according to
the motor characteristics.
Ａ
• Can be used for load reduction in accordance with
the cooling performance at a low speed.
• When the first electronic thermal level [bC110] is
64 A, the reduction ratio is ×0.8 for operations at a
base frequency of 60 Hz and output frequency of
20 Hz and the electronic thermal time-limited
characteristics are given in the lower part of
Example 2.
• Since Example 1 shows the case of the reduction
ratio ×1, a trip occurs in 60 s when an electric
current of 150% ×1 of the ND rated current flows
continuously. However in Example 2, a trip occurs
in 60 s when an electric current of
150%×0.8=120% of the ND rated current flows
continuously.
12-7-2
Inverter Functions
Description