Hitachi SJ700-2 - Manual (Page 100)

Chapter 4 Explanation of Functions
4.2.29 Electronic thermal protection
The electronic thermal protection function allows you to protect
the motor against overheating. Make settings of this function
based on the rated current of the motor. The inverter will trip for
overheat protection according to the settings.
This function provides optimum overheat protection that is also
designed with the lowering of the motor's cooling performance
at low speeds in mind. b012/b212/b312: Electronic thermal setting
(calculated within the inverter from current output),
1st/2nd/3rd motors
b013/b213/b313: Electronic thermal characteristic,
1st/2nd/3rd motors
b015/b017/b019: Free setting, electronic thermal
frequency (1) (2) (3)
b016/b018/b020: Free setting, electronic thermal
current (1) (2) (3)
C021 to C025: Terminal [11] to [15] functions
C026: Alarm relay terminal function
C061: Electronic thermal warning level setting
Related code
You can configure this function so that the inverter outputs a
warning signal before it trips for electronic thermal protection.
(1) Electronic thermal level
Item Function code Range of data Description
Electronic thermal
setting (calculated within
the inverter from current
output)
b012/b212/b312
"0.2 x rated current" to
"1.0 x rated current"
See the example below.
60
3.0
69.8
(109%)
0 96
(150%)
128
(200%)
Trip time (s)
Motor current (A)
(Ratio to the rated
current of inverter)
(Example) Setting on the SJ700-150LFF
Rated
current: 64 A
Range of setting: 12.8 A (20%) to 64.0 A (100%)
When 64 A is set as the electronic thermal setting (b012),
the time-limit characteristic is as shown on the right.
(2) Electronic thermal characteristic
The frequency characteristic set as the electronic thermal characteristic is integrated with the value of
"b012", "b212", or "b312".
The cooling-fan performance of a general-purpose motor lowers when the motor speed is low. So load
(current) is decreased.
The reduced-torque characteristic is designed to match the heat generation by Hitachi's general-purpose
motors.
Item Function code Data Description
00 Reduced-torque characteristic
01 Constant-torque characteristic
Electronic thermal
characteristic
b013/b213/b313
02 Free setting of electronic thermal characteristic
(a) Reduced-torque characteristic
The time-limit characteristic determined by the value of "b012", "b212", or "b312" is integrated with each
frequency multiplied by reduction scales.
Example) Setting on the SJ700-150LFF (rated current: 64 A)
When "b012" is 64 A, the base frequency is 60 Hz,
and output frequency is 20 Hz:
X1.0
5 16 50
X0.8
X0.6
0
6 20 60 0
Reduction
scale
Base frequency
Inverter output
frequency (Hz)
55.8
(87.2%)
76.8
(120%)
102.4
(160%)
0
60
3.0
Trip time (s)
Motor current (A)
(Ratio to the rated
current of inverter)
4 -
37