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Chapter 4 - Parameter Description [FU1]
46
FU1-50: Electronic Thermal (Motor i
2
t) Selection
FU1-51: Electronic Thermal Level for 1 Minute
FU1-52: Electronic Thermal Level for Continuous
FU1-53: Electronic Thermal Characteristic (Motor
type) Selection
These functions are to protect the motor from
overheating without using additional thermal
overload relay. Inverter calculates the
temperature rise of the motor using several
parameters and determines whether or not the
motor is overheating. Inverter will turn off its
output and display a trip message when the
electronic thermal feature is activated.
This function activates the ETH parameters by
setting ‘Yes’.
This is the reference current when the inverter
determines the motor has overheated. Inverter
trips in 1 minute when 150% of rated motor
current established in FU2-33 flows for 1 minute.
☞
Note: The set value is the percentage of FU2-33 [Rated Motor
Current].
This is the current at which the motor can run
continuously. Generally, this value is set to ‘100%’
and which means the rated motor current set in
FU2-33. This value must be set less than FU1-51
[ETH 1min].
☞
Note: The set value is the percentage of FU2-33 [Rated Motor
Current].
[Motor i
2
t Characteristic Curve]
To make the ETH function (Motor i
2
t) work
correctly, the motor cooling method must be
selected correctly according to the motor.
[Self-cool] is a motor that has a cooling fan
connected directly to the shaft of the motor.
Cooling effects of a self-cooled motor decrease
when a motor is running at low speeds. The motor
current is derated as the motor speed decreases.
[Forced-cool] is a motor that uses a separate
motor to power a cooling fan. As the motor speed
changes, the cooling effect does not change.
[Load Current Derating Curve]
☞
Note: Despite the motor current changing frequently due to
load fluctuation or acceleration and deceleration, the inverter
calculates the i
2
t and accumulates the value to protect the
motor.
Load Current [%]
Trip Time
FU1-51
[ETH 1min]
1 minute
FU1-52
[ETH cont]
100%
95%
65%
Output Current
20Hz 60Hz
Self-Cool
Forced-Cool