Siemens LMV5 Series Technical Instructions page 164

Technical Instructions LMV Series
Document No. LV5‐1000
NOTE: The total time of the standardization shown in Figure 5‐3 is 70 seconds with a VFD ramp time
of 30 seconds. Longer VFD / LMV52 ramp times will increase the total time taken for the
standardization.
NOTE: The VFD is spanned so 20mA = 62Hz. Thus, 19.5mA is approximately 60Hz.
Based off of the RPM that was read at 19.5 mA (in this case 3544 RPM) and an assumption of 0 RPM at
minimum signal (typically 4mA), a two point linear interpolation is automatically done by the LMV52,
which establishes the linear relationship between the analog signal and the blower RPM . This
relationship is shown in Figure 5‐4.
Figure 5‐4: Result of Standardization (2‐pole blower motor) and Analog Signal Correction Limits
When the burner is in operation, the LMV52 has active, closed‐loop control of the blower motor speed
and can compensate for motor slip and other factors within limits. The analog signal can be increased to
compensate for low blower RPM and decreased to compensate for high blower RPM. These analog
signal limits are also shown in Figure 5‐4.
If the analog signal is increased to the maximum allowable signal and the blower RPM is still low, a
message will be displayed on the AZL that states "Fan speed not reached".
Section 5 Page 12 SCC Inc.
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