2nd edition, 31-03-2020
7000.05061, 2nd edition, 31-03-2020
7000.05061
Description of functions
37
If the calculated model temperature reaches a critical value (T
crit
), the current controller
comes into effect and limits the motor current to the continuous current (I
cont
).
Area II:
As in this area the calculated model temperature reaches the critical temperature (T
crit
)
as a result of the change in load (X
1
), the current controller adjusts the motor current to
the continuous current (I
cont
).
Area III:
The current in the motor becomes less and less as a result of the change in load (X
2
).
The calculated model temperature is below the critical temperature (T
crit
) so that the
current controller no longer needs to intervene.
5.5.2
Overtemperature shutdown
If the temperature of the electronics exceeds 100 °C, the motor is deactivated.
CAUTION!
Risk of injury caused by automatic starting of the motor.
As soon as the electronics temperature drops below approx. 95°C, the motor is activated
again automatically.
Attach suitable guards.
5.6
Voltage output at motor
The power stage of a motor with Speed Controller uses pulse width modulation (PWM). In
the case of a fixed PWM frequency, the duty cycle between the switch-on time and switch-
off time is set according to the controller output value. Since in the case of pulse width
modulation the inductance of the motor acts as a current filter, a high PWM frequency is
selected (96 kHz and 24 kHz with BRC, 32…BXT H and 42…BXT H motors). This method is
extremely energy-efficient. A comparatively low amount of heat is generated.
At the operating point, set a duty cycle as large as possible. When doing so, observe the
required control reserve. This may require the motor supply voltage to be reduced.
If the permissible maximum housing temperature is observed in PWM mode, the maximum
possible continuous torque may be less than with full modulation. In this case, the maxi-
mum thermally permissible continuous current drops.
With a small PWM duty cycle and a large motor load, a high current flow is briefly gen-
erated. This results in higher losses, i.e. a large amount of heat is generated.
A reduction in efficiency at the motor causes a reduction in the maximum permissible
current. The maximum torque also decreases as a result.
