Hitachi SJ Series, User Manual

Page: 201 / 786

12-7-2
Chapter 12 Inverter Functions
Change of electronic thermal characteristics
• Want to make protection taking account of the
cooling function at a low speed.
• Want to change the thermal protection setting
pattern freely.
• 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
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
• 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.
• 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.
Item Parameters Data Description
First electronic
thermal
characteristics
selection
[bC111]
00
Reduced torque characteristics:
Pattern for cooling function deterioration at a
low speed
01
Constant torque characteristics:
Pattern for constant output
02
Free setting:
Multiple patterns are available according to
the motor characteristics.
Ｑ
Ａ
！
Ａ
Reduction ratio
Output frequency
(Hz)
X1.0
5 16 50
X0.8
X0.6
0
6 20 60
0
Base frequency
55.8
(87.2%)
76.8
(120%)
102.4
(160%)
Output current (A)
(Ratio to ND rated
current)
60
3.0
Trip time (s)
×1
×0.8