Application Specific Features
7.10 Process Availability - The Perfect Harmony Advantage
Product User Manual
Operating Instructions, Version AE 12/2009, A5E01454341C
171
7.10 Process Availability - The Perfect Harmony Advantage
Process availability is the primary prerequisite for applying a Medium Voltage VFD system in
a process critical application. By combining the capabilities of Perfect Harmony’s unique
distributed power architecture with the power of the NXG control and the patented power cell
bypass feature, it is possible to deliver unparalleled opportunities for improved process
availability. It is also essential that the process operator receive complete and accurate
information on VFD status, to allow for process adjustments that can preclude process trips
and disruptions in process capability.
7.10.1 What is ProToPSTM?
ProToPS™ is an acronym that stands for "Process Tolerant Protection Strategy."
ProToPS™ is a standard implementation of the VFD SOP (System Operating Program). The
ProToPS™ goal is simply to put the process operator in control of the process. ProToPS™ is
a system program implemented from a customer process perspective.
ProToPS™ provides the operator with indication of a change in state in the VFD. These
annunciations identify changes that can impact the ability of the VFD to meet process
demands, or to provide advance indication of a pending VFD trip. ProToPS™ allows the
process operator to make process corrections to maintain the VFD in service, or adjust the
process to address a pending VFD trip.
With ProToPS™, the process operator not only knows the general status of the VFDs, but
also understands the VFD condition that has caused the general alarm to exist.
7.10.2 How does ProToPSTM Work?
ProToPS™ takes the standard fault indications available in the VFD and categorizes them
into four basic major categories as follows:
1. Alarm - An alarm is an indication that a VFD parameter limit has been reached, or that a
VFD system condition is present. An alarm provides the operator with awareness of the
condition, but demands no immediate action. Examples of alarms include: over-voltage,
under-voltage, and ground fault.
2. Process Alarm - A process alarm is an indication that a VFD parameter limit has been
exceeded and that the process either should be limited, or that the VFD capacity to meet
the process demand is limited. Examples of process alarms include thermal limits above
the rated limit, and the condition of a cell having been bypassed.
3. Trip Alarm - A trip alarm provides a clear indication that a VFD high parameter limit has
been reached. A trip alarm is an indication that a VFD trip is pending. The operator
receives a message that, unless the alarm can be cleared by a process change, the VFD
will trip.
4. Trip - Certain VFD faults cannot be provided with advance warning. This limited number
of faults will result in a VFD trip. A trip message is also annunciated when a trip alarm
time limit has been exceeded. The number of mandated trips is considerably reduced
with the implementation of GENIV cell bypass.
With ProToPS™ the (VFD Run) signal is maintained as "true" and the (VFD Trip) signal is
maintained as "false" for all alarm states.
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