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VAR Names Index Type Comment
VAR nvoAlarmword 34 83 SNVT_state Bit 01 indicates that the drive is tripped off and
that power to the drive will have to be cycled to
be able to reset the trip
VAR nvoOutputPcnt 35 81 SNVT_lev_percent
VAR nvoOutputHz 36 76 SNVT_freq_hz Units: Hz
VAR nvoStatusword 37 83 SNVT_state Bit 08 Drive Running at reference
Bit 07 Drive has warnings
Bit 03 Drive has tripped off
VAR nvoDrvStatus 38 83 SNVT_state Bit 13 Running at reference
Bit 14 Drive has warnings
Bit 11 Drive has tripped off
VAR nvoDrvEnrg 39 13 SNVT_elec_kwh Units: kWh
VAR nvoDCVoltage 40 44 SNVT_volt
VAR nvoTempMtr 41 21 SNVT_lev_cont
VAR nvoTempInvrtr 42 21 SNVT_lev_cont
VAR nvoFeedback 43 81 SNVT_lev_percent
VAR nvoAnalog1 44 44 SNVT_volt
VAR nvoAnalog2 45 44 SNVT_volt
VAR nvoAnalog3 46 2 SNVT_amp_mil
VAR nvoOutputHz1 47 76 SNVT_freq_hz
If parameter 100 is set for “Closed Loop”, then nvoOutputPcnt, nvoOutputHz and nvoOutputRads do NOT
represent output speed. Instead, they represent the value of the feedback signal. When operating in closed loop
mode this is monitored as the value of the controlled variable - the feedback. The speed of the drive doesn’t really
matter as long as the feedback signal is correct.
For practical purposes, nvoOutputPcnt is the one that is useful in closed loop mode, since it provides the information
that is the easiest to understand. It represents the percent of the feedback signal from MIN. REFERENCE (parameter
204) to MAX. REFERENCE (parameter 205). It is generally best to define MIN. REFERENCE (parameter 204) = MIN.
FEEDBACK (parameter 413) and MAX. REFERENCE (parameter 205) = MAX. FEEDBACK (parameter 414). In this
way nvoOuptutPcnt is also a percent of the feedback sensor’s range, which is what most people expect.
Trane TR1 drives are supplied with multiple, active reference signals, that are typically added together. You can turn off
summation by setting the appropriate MIN. REFERENCE (parameter 204) = 0. The analog “nvo” values are based on
the REFERENCE range. Therefore, if the drive is running at minimum reference, all three of these values nvoOutputPcnt,
nvoOutputHz, and nvoOutputRads will show up as being zero. It is suggested to set parameter 204, Minimum
Reference, to 0. In that way nvoOutputPcnt, nvoOutputHz, and nvoOutputRads will read as expected
Also parameters 503 through 508 allow some prioritizing of source of the reference signals.
Start/Stop:
LonWorks has two ways of handling this.
The most common method is to simply use nviStartStop. This ramps the drive both for starting and stopping as used
in the AH540.
A second method is to use nviControlWord. This 16-bit word allows a wider range of control of the drive, such as coast
to stop and locking out all start commands (like a safety interlock). This is generally viewed as being overkill by most
people and not supported by Tracer Summit. Either of these can be set to interact with the drive’s control terminals
(a.k.a. digital inputs). Drive parameters 503 through 508 allow a selection of “SERIAL PORT”, “DIGITAL INPUT”,
“LOGIC OR” and “LOGIC AND” for a variety of functions.
