8.6.3 Digital low-voltage PWM signal
The square-wave PWM signal is designed for a frequency range
of 100 to 1500 Hz for the standard input profiles. The PWM signal is
used to select the speed (speed command) and as feedback signal.
The PWM frequency on the feedback signal is fixed at 75 Hz in the
pump.
Duty cycle
d % = 100 × t/T
Example Rating
T = 2 ms (500 Hz)
U
IH
= 4-24 V
t = 0.6 ms
U
IL
≤ 1 V
d % = 100 × 0.6 / 2 = 30 %
4.5 mA ≤ IH ≤ 10 mA (depending on
U
IH
)
Example
TM049911
PWM signal
Abbreviation Description
t Duration of the pulse signal [s]
T Total period of time [s]
U
IH
High-level input voltage
U
IL
Low-level input voltage
8.6.4 PWM input signal profile A (heating)
At high PWM signal duty cycles, a hysteresis prevents the pump
from starting and stopping if the input signal fluctuates around the
shifting point. At low PWM signal duty cycles, the pump speed is
high for safety reasons. In case a cable breaks when mounted
in a system, the pump starts to run at maximum speed. This
is suitable for both boilers and heat pumps to ensure that the pump
transfers heat even if a cable breaks.
Max.
Min.
10
20
30 40
50 60 70
80
90
100
X
Y
TM049985
PWM input profile A (heating)
Axis Value
X Input duty cycle
Y Speed
PWM input duty cycle Pump status
PWM signal ≤ 10 % Max. speed
10 % < PWM signal ≤ 84 %
Variable speed from min. to max.
speed
84 % < PWM signal ≤ 91 % Min. speed
91 % < PWM signal ≤ 95 % Hysteresis area: on/off
95 % < PWM signal ≤ 100 % Standby mode: off
16
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