Hitachi SJ300 Series Thermal Warning Signal

4–55

SJ300 Inverter

Opt.

Symbol

Function Name

Output

Description

Code

State

Valid for

11, 12, 13, 14, 15,

Example: (Requires output configuration—

outputs:

AL0 – AL2

see page 3–53.)

Required

B034

Inverter output

settings:

terminal circuit

Notes:

RNT or

• The two outputs [RNT] and [ONT] share the

ONT

same time threshold parameter, B040.

14

13

11

Typically, you will use either the [RNT] or the

15

CM2

12

[ONT] output only—not both at once.

•These outputs are useful for the notification that a preventative maintenance interval has expired.

+

RY –

See I/O specs on page 4–9.

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.

Function	Function/Description	Data or Range
Code
B012 / B212	Electronic thermal setting (calculated	Range is 0.2 * rated current to
/ B312	within the inverter from current output)	1.2 * rated current

Operations Monitoring and

For example, suppose you have inverter model SJ300-110LFE. The rated motor current is 46A. The setting range is (0.2 * 46) to (1.2 *46), or 9.2A to 55.2A. For a setting of B012=46A (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.

Trip

time (s)

60
0.5
0			A
53.4	69	92
116%	150%	200%

Trip current at 60 Hz