Siemens LMV37.4 Series - Safe Separation of Mains Voltage and Protective Extra Low-Voltage; Ramp Time

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Building Technologies Basic documentation LMV37.4... CC1P7546en
12 Fan control 17.12.2018
12.5 Safe separation of mains voltage and
protective extra low-voltage
Caution!
All inputs and outputs of PWM fan control are designed for use with protective
extra low-voltage. For this reason, strict separation from the mains voltage side
must be ensured!
This necessitates an external power supply by the VSD or an external power pack (X74
pin 1, X74 pin 2).
LMV...
Bild 433en/0916
VSD X74
5
4
3
Power output
2 GND
1 24 V external
Figure 83: Power output

Note
Power must also be supplied via X74 pin 1 / pin 2 in the case a PWM fan is used.
12.6 Ramp time
The ramp time for fan control can be set separately for acceleration and deceleration
(also refer to chapter Traveling speed/maximum curve slope).
No. Parameter
522 Ramp up
523 Ramp down
544 Ramp modulating
If shutdown occurs because the speed has not been reached, the VSD/fan motor might
not be able to follow quickly enough the set ramp.
In the case of a ramp time >20 seconds, the modulating operating ramp (parameter
544) must be increased (refer to chapter Running speed / maximum curve slope).
Remedy:
Shorten further the ramp of the VSD/fan motor or increase the ramp in the LMV37.4
(parameters 522/523) (also refer to chapter Traveling speed/maximum curve slope).
Caution!
The ramps parameterized for the VSD should be at least 20% shorter than the
ramps in the LMV37.4.
Example:
5 s ramp LMV37.4 4 s ramp VSD
10 s ramp LMV37.4 8 s ramp VSD
20 s ramp LMV37.4 16 s ramp VSD
40 s ramp LMV37.4 32 s ramp VSD
For VSD operation