Hitachi SJ700-2 Electronic thermal protection, Function code Data Description Electronic thermal

Motor current (A) (Ratio to the rated current of inverter)

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.

You can configure this function so that the inverter outputs a warning signal before it trips for electronic thermal protection.

(1) Electronic thermal level

Related code

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

Item	Function code	Range of data	Description
Electronic thermal
setting (calculated within	b012/b212/b312	"0.2 x rated current" to	See the example below.
the inverter from current		"1.0 x rated current"
output)

(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.

Trip time (s)

60

3.0

069.8 96 128

(109%) (150%) (200%)

(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
Electronic thermal	b013/b213/b313	00	Reduced-torque characteristic
		01	Constant-torque characteristic
characteristic
		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.

Reduction scale

X1.0

X0.8

X0.6

				Inverter output
0	5	16	50	frequency (Hz)
0	6	20	60

Base frequency

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:

Trip time (s)

60

3.0

055.8 76.8 102.4 Motor current (A)

(87.2%) (120%) (160%) (Ratio to the rated current of inverter)

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