Configuring Vfds For Use With The Lmv52 - Siemens LMV5 Series Technical Instructions

Technical Instructions
Document No. LV5‐1000
2. The static output pressure of the blower (SP) varies by the square of the change in RPM:
3. The required brake horsepower of the blower (BHP) varies by the cube of the change in RPM:
Example: A blower spinning at 1750 RPM produces 10 in WC of static pressure, 4500 CFM of flow, and
requires 20 BHP. What happens if the RPM is increased to 2750 RPM?
Assumptions: Air damper is wide open, and system effects (such as the restriction due to the boiler's
heat exchanger, the burner's diffuser, etc...) are not taken into account.
Flow: CFM (new) = (2750 / 1750) * 4500 = 7071 CFM
Pressure: SP (new) = (2750 / 1750)
Power: BHP (new) = (2750 / 1750)
Configuring VFDs for use with the LMV52
Modern VFDs typically have hundreds of parameters that can be set to tailor the VFD to a specific
application. As mentioned earlier, there are also at least a hundred different manufacturers of VFDs,
each of which have their own unique parameter list. Due to these two factors, SCC Inc. offers pre‐
programmed VFDs that can be purchased with the VFD parameters set up for use with an LMV52.
If a VFD for use with an LMV52 is purchased and programmed independently, the following points will
serve as a general guideline for programming the VFD for the LMV52 application. Note that this
guideline is necessarily general due to the variety of VFDs offered in the marketplace.
1. If a Vector VFD is used (recommended), set the "Control Method" to Open Loop Vector mode or
equivalent.
2. The stopping method (after the run / stop contact is opened) should be set to "Coast to Stop" to let
the motor coast to a stop after post‐purge.
3. Reverse operation (the ability to reverse the motor with an input) should be disabled.
4. Configure the VFD to accept an external run / stop signal via the dry contact on the LMV52.
Section 5 Page 8 SCC Inc.
2
* 10 = 24.7 in WC
3
* 20 = 78 BHP
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