4.13.1 Motor protection from overheat (Electronic thermal relay function) (Pr. 9, Pr. 51)
*1 The initial value of the 0.4K and 0.75K is set to 85% of the rated inverter current.
*2 When parameter is read using the FR-PU04, a parameter name different from an actual parameter is displayed.
(1) Electronic thermal relay function operation characteristic (THM)
Purpose Parameter that must be Set Refer to Page
Motor protection from overheat Electronic thermal O/L relay Pr. 9, Pr. 51 183
Use the constant torque motor Applied motor Pr. 71 187
The motor performance can be maximized for operation in magnetic flux vector control system
Offline auto tuning Pr. 82 to Pr. 84,
Pr. 90 to Pr. 94, Pr. 96 189 High accuracy operation unaffected
by the motor temperature and stable operation with high torque down to ultra low speed are performed
Online auto tuning Pr. 95, Pr. 574 199
Set the current of the electronic thermal O/L relay to protect the motor from overheat. This feature provides the optimum protective characteristics, including reduced motor cooling capability, at low speed.
Parameter
Number Name Initial Value Setting Range Description
9 Electronic thermal O/L relay
Rated inverter current *1
55K or lower 0 to 500A
Set the rated motor current.
75K or higher 0 to 3600A 51 Second electronic
thermal O/L relay *2 9999
55K or lower 0 to 500A Valid when the RT signal is ON.
Set the rated motor current.
75K or higher 0 to 3600A
9999 Second electronic thermal O/L relay invalid
[Electronic thermal relay function operation characteristic (E.THM)] This function detects the overload (overheat) of the motor, stops the operation of the inverter's output transistor, and trips. (The operation characteristic is shown on the left)
⋅ Set the rated current [A] of the motor in Pr. 9. (If the motor has both 50Hz and 60Hz rating and the Pr. 3 Base frequency is set to 60Hz, set the 1.1 times of the 60Hz rated motor current.)
⋅ Set "0" in Pr. 9 when you do not want to activate the electronic thermal relay function, e.g. when using an external thermal relay with the motor. (Note that the output transistor protection of the inverter functions (E.THT).)
⋅ When using the Mitsubishi constant-torque motor 1) Set "1" or any of "13" to "18", "50", "53", "54" in Pr. 71.
(This provides a 100% continuous torque characteristic in the low-speed range.)
2) Set the rated current of the motor in Pr. 9.
*1 When 50% of the rated inverter current (current value) is set in Pr. 9
*2 The % value denotes the percentage to the rated inverter current. It is not the percentage to the motor rated current.
*3 When you set the electronic thermal relay function dedicated to the Mitsubishi constant-torque motor, this characteristic curve applies to operation at 6Hz or higher. (Refer to page 187 for the operation characteristic.)
CAUTION
⋅ Fault by electronic thermal relay function is reset by inverter power reset and reset signal input. Avoid unnecessary reset and power-off.
⋅ When using multiple motors with one inverter, or using a multi-pole motor or a specialized motor, provide an external thermal relay (OCR) between the inverter and motor. And for the setting of the thermal relay, add the line-to line leakage current (refer to page 52) to the current value on the motor rating plate. For low-speed operation where the cooling capability of the motor reduces, it is recommended to use a thermal protector or thermistor-incorporated motor.
⋅ 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 this case, use an external thermal relay.
⋅ Since a thermal protector is built in a motor dedicated for vector control (SF-V5RU), set "0" in Pr. 9 to use the motor Electronic thermal relay
function for transistor protection 52.5% 105%
50 100 150
60 120 180 240 50 60 70
6Hz
20Hz 10Hz 6Hz 0.5Hz 30Hz or more*3
20Hz 10Hz
0.5Hz Pr. 9 = 50% setting of inverter rating*1.2
Pr. 9 = 100% setting of inverter rating*2
(s) unit display in this region(min) unit display in this region Operation time (min)Operation time (s)
Characteristic when electronic thermal relay function for motor protection is turned off (When Pr. 9 setting is 0(A)) 30Hz
or more*3
Inverter output current(%) (% to the rated inverter current)
Operation region Region on the right of characteristic curve Non-operation region Region on the left of characteristic curve
(2) Electronic thermal relay function operation characteristic (THT)
Electronic thermal relay function (transistor protection thermal) operation characteristics of the inverter when the ratio of the motor current to the inverter rated current is presented as transverse is shown. Transverse is calculated as follows: (motor current [A]/inverter rated current [A]) × 100 [%].
Optimum Conditions Inverter Capacity
55K or lower 75K or higher
Running frequency : 1Hz or more Carrier frequency: 2kHz
Running frequency : 1Hz or less Carrier frequency: 2kHz
CAUTION
⋅ Fault by electronic thermal relay function is reset by inverter power reset and reset signal input. Avoid unnecessary reset and power-off.
⋅ The operation time of the transistor protection thermal relay shortens when the Pr. 72 PWM frequency selection setting increases.
0 30 60 90 120 150
0 25 50 75 100 125 150 175 200 Ratio of the motor current to the inverter rated current (%)
Operation time (S)
0 30 60 90 120 150
0 25 50 75 100 125 150 175 200 Ratio of the motor current to the inverter rated current (%)
Operation time (S)
0 3 6 9 12 15
0 25 50 75 100 125 150 175 200 Ratio of the motor current to the inverter rated current (%)
Operation time (S)
0 3 6 9 12 15
0 25 50 75 100 125 150 175 200 Ratio of the motor current to the inverter rated current (%)
Operation time (S)
Selection and protection of a motor
4
P ARAME T E RS
(3) Set multiple electronic thermal relay functions (Pr. 51)
(4) Electronic thermal relay function pre-alarm (TH) and alarm signal (THP signal) Use this function when rotating two motors of different rated currents individually by a
single inverter. (When rotating two motors together, use external thermal relays.)
⋅ Set the rated current of the second motor in Pr. 51.
⋅ When the RT signal is ON, thermal protection is provided based on the Pr. 51 setting.
REMARKS
⋅ The RT signal acts as the second function selection signal and makes the other second functions valid. (Refer to page 235)
⋅ The RT signal is assigned to the RT terminal in the initial setting. By setting "3" in any of Pr. 178 to Pr. 189 (input terminal function selection), you can assign the RT signal to the other terminal.
100%: Electronic thermal relay function alarm operation value ⋅ The alarm signal (THP) is output and an electronic thermal pre- alarm (TH) is displayed when the electronic thermal relay function cumulative value reaches 85% of the level set in Pr. 9 or Pr. 51. If it reaches 100% of the Pr. 9 Electronic thermal O/L relay setting, electronic thermal relay function protection (E.
THM/E.THT) occurs.
⋅ The inverter does not trip if the alarm signal is output.
⋅ For the terminal used for the THP signal output, assign the function by setting "8" (positive logic) or "108" (negative logic) in any of Pr. 190 to Pr. 196 (output terminal function selection).
CAUTION
⋅ Changing the terminal assignment using Pr. 190 to Pr. 196 (output terminal function selection) may affect the other functions. Set parameters after confirming the function of each terminal.
.... Output current value is used to perform integration processing.
.... Output current is assumed as 0A to perform integration processing. (cooling processing)
×... Electronic thermal relay function is not activated.
Pr. 450
Second applied motor
Pr. 9
Electronic thermal O/L relay
Pr. 51
Second electronic thermal O/L relay
RT = OFF RT = ON First
motor
Second motor
First motor
Second motor
9999 0
9999 × × × ×
0 × × × ×
0.01 to 500 (0.1 to 3600) × ×
9999 Other than 0
9999 × ×
0 × ×
0.01 to 500 (0.1 to 3600) Other than
9999 0
9999 × × × ×
0 × × × ×
0.01 to 500 (0.1 to 3600) × ×
Other than 9999
Other than 0
9999
0 × ×
0.01 to 500 (0.1 to 3600)
RT
MC
MC W
V U
IM IM
SD
OFF ON
100%
85%
ON Time Electronic thermal
relay function operation level Electronic thermal O/L relay alarm (THP)
(5) External thermal relay input (OH signal)
(6) PTC thermistor input (PTC signal)
Built-in PTC thermistor of the motor can be input to the PTC signal (AU terminal).
⋅ For the terminal used for PTC signal input, assign the function by setting "63" in Pr. 184 AU terminal function selection and also set the AU/PTC switchover switch to the PTC terminal function. (The initial setting is the AU terminal function.)
⋅ If a motor overheat state is detected for more than 10s according to the input from the PTC thermistor, the inverter trips and outputs the PTC thermal fault signal (E.PTC).
External thermal relay input connection example
⋅ To protect the motor against overheat, use the OH signal when using an external thermal relay or the built-in thermal protector of the motor.
⋅ When the thermal relay operates, the inverter trips and outputs the fault signal (E.OHT).
⋅ For the terminal used for OH signal input, assign the function by setting "7" in any of Pr. 178 to Pr. 189 (input terminal function selection)
⋅ A thermal protector is provided for a vector control dedicated motor (SF-V5RU).
* Assign OH (external thermal input) signal to the CS terminal.
(Pr. 186 = "7")
Connect a 2W1kΩ resistor between the terminal PC and CS(OH).
Install the resistor pushing it against the bottom part of the terminal block so as to avoid a contact with other cables.
Refer to page 231 for details of Pr. 186 CS terminal function selection.
CAUTION
⋅ Changing the terminal assignment using Pr. 178 to Pr. 189 (input terminal function selection) may affect the other functions. Set parameters after confirming the function of each terminal.