TCI HG7 - Manual (Page 22)

I N T R O D U C T I O N
INTRODUCTION HG7 I, O, & M Manual 20
HG7 XM Schematic: 450 – 600 HP based on 480V
When possible, the “Up to Speed” Auxiliary Contacts should be used instead of the “Run-Stop” Auxiliary
Contacts on the VFD. Detailed note below.
NOTE 1 Detail:
When possible, the “Up to Speed” Auxiliary Contacts should be used instead of the “Run-Stop” Auxiliary Contacts
on the VFD.
Benefits of this setup:
1. Most electrical systems have generator back-up systems today. The filters will start-up with no
capacitance in the circuit. On generator applications this allows the voltage regulator and the load to
stabilize before the capacitors are brought into the circuit eliminating spiking and potential leading power
factor condition.
2. This will potentially prevent a leading power factor condition on the Bus, especially when many VFDs with
filters are on the same Bus. For example, if the VFD at speed reference is programmed for 45 hertz, the
contactor is open at speeds less than 45Hz. The capacitors will be off-line when the frequency drops
below this reference. The capacitors will be closed above the 45Hz programmed contact closure for
normal harmonic mitigation.
On variable torque fan and pump loads the current drops dramatically below a 60 hertz operation and as
a result there will be too many vars of capacitance in the system for the load applied. The result will lead
to a high voltage condition at the input terminals of the VFD, potentially causing an “overvoltage” trip.