M5.7-1 I²t nominal motor current “NomCurr”
M5.7-2 I²t start motor temperature “I2tTemp”
M5.7-3 I²t time “I2tTime”
M5.7-4 I²t cutback1 “I2tCutB1”
M5.7-5 I²t cutback2 “I2tCutB2”
M5.7-6 I²t cutback3 “I2tCutB3”
It is HIGLY RECOMMENDED to avoid using this function on Walkie-type vehicles with
speed control mode. This could lead to serious safety problems and cause operator’s
injuries.
DMC declines any responsibility for incorrect setup of this parameters.
These settings are part of I
2
t function (pronounce as “I-squared-t”), that is a current limiting feature: the
maximum current is limited with time.
A detailed description of the function and how to set its parameters is following.
Heat dissipation
When current is flowing through the motor some electrical losses are present (since the motor is not ideal) and
they result in heating up the motor. The heat dissipation is a squared function of the current multiplied by the
motor’s resistance, as shown in the following equation:
The resistance of the motor is a constant factor (although it would increase with a temperature rise). The heat
dissipation will heat up the motor. The longer heat is dissipated, the more the motor will heat up. How fast the
motor heats up depends on the amount of current flowing through the motor. A large current will heat up the
motor faster than a smaller current.
Insulation classes
The heat dissipation results in increasing the motor temperature. The maximum allowable operation
temperature of the motor depends on the insulation class the motor is designed for. The rule here is that there
is a ‘temperature rise’ upon the reference ambient temperature (often 40 °C). Often an allowance for ‘hot spot’
winding is also taken into consideration (usually 10 °C). This results in the following equation:
When completing this for several insulation classes, it leads to the following table.
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