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Operation characteristics of
electronic thermal relay function
Pr.9 = 50% setting
of inverter rating
∗1, 2
70
30 Hz
or more
∗3
20 Hz
60
10 Hz
6 Hz
0.5 Hz
50
240
180
120
60
52.5%
105%
50
100
Inverter output power (%)
(% to the inverter rated current)
NOTE
• The internal accumulated heat value of the electronic thermal relay function is reset by inverter power reset and reset signal
input. Avoid unnecessary reset and power-OFF.
• When the inverter is used to drive a multi-pole motor or a dedicated motor, install an external thermal relay (OCR) between
the inverter and the motor. Note that the current indicated on the motor rating plate is affected by the line-to-line leakage
current (refer to
• The cooling effect of the motor drops during low-speed operation. Use a thermal protector or a motor with built-in thermistor.
• When the difference between the inverter and motor capacities is large and the setting is small, the protective characteristics
of the electronic thermal relay function will be deteriorated. In such case, use an external thermal relay.
• A dedicated motor cannot be protected by an electronic thermal O/L relay. Use an external thermal relay.
• Motor over temperature sensing is not provided by the drive.
Rated specifications per inverter
The following table shows the rated specifications per inverter. (For the rated specifications for operating two or three inverters
in parallel, refer to
page
106.)
Model FR-A842-[ ]-P
Applicable motor capacity (kW)
Rated capacity (kVA)
Rated current (A)
Overload current rating
Rated voltage
DC power supply voltage
Control power supply auxiliary input
Permissible control power supply auxiliary input fluctuation
Protective structure (IEC 60529)
Approx. mass (kg)
The applicable motor capacity indicated is the maximum capacity applicable for use of the Mitsubishi Electric standard 4-pole motor.
The rated output capacity indicated assumes that the output voltage is 440 V.
The % value of the overload current rating indicated is the ratio of the overload current to the inverter's rated output current. For repeated duty,
allow time for the inverter and motor to return to or below the temperatures under 100% load.
The maximum output voltage does not exceed the power supply voltage. The maximum output voltage can be changed within the setting range.
However, the maximum point of the voltage waveform at the inverter output side is the power supply voltage multiplied by about
FR-DU08: IP40 (except for the PU connector section)
For the power voltage exceeding 480 V, set Pr.977 Input voltage mode selection. (For details, refer to the FR-A800 Instruction Manual
(Detailed).)
116
APPENDIX
This function detects the overload (overheat) of the motor and trips the
inverter by stopping the operation of the transistor at the inverter output side.
(The operation characteristic is shown on the left.)
Pr.9 = 100% setting
of inverter rating
∗2
• Mitsubishi Electric constant-torque motor
30 Hz
Operation region
∗3
or more
Region on the right of
characteristic curve
20 Hz
(1) Set one of "1" or "13 to 16" in Pr.71. (This setting will enable the 100%
Non-operation region
10 Hz
Region on the left of
characteristic curve
6 Hz
constant-torque characteristic in the low-speed range.)
0.5 Hz
Characteristic when
electronic thermal relay
(2) Set the rated current of the motor in Pr.9.
function for motor
protection is turned off
(When Pr.9 setting is 0(A))
Range for
the transistor
protection
∗4
150
230
page
68) when selecting the setting for an external thermal relay.
LD
ND (initial setting)
LD
ND (initial setting)
LD
ND (initial setting)
LD
ND (initial setting)
When a value 50% of the inverter rated output current (current value) is set in Pr.9
The % value denotes the percentage to the rated inverter current. It is not the
percentage to the rated motor current.
When you set the electronic thermal relay function dedicated to the Mitsubishi
Electric constant-torque motor, this characteristic curve applies to operation at 6
Hz or higher.
Transistor protection is activated depending on the temperature of the heat sink.
The protection may be activated even with less than 150% depending on the
operating conditions.
400K
09620
360
400
320
360
470
528
417
470
692.8
769.6
616
692.8
120% 60 s, 150% 3 s (inverse-time characteristics) at surrounding air
temperature of 50°C
150% 60 s, 200% 3 s (inverse-time characteristics) at surrounding air
temperature of 50°C
Three-phase 380 to 500 V
430 to 780 VDC
Single phase 380 to 500 V 50/60 Hz
Frequency 5%, voltage 10%
Open type (IP00)
243
243
450K
500K
10940
12120
450
400
586
528
875.2
769.6
243
.
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