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Cable fittings
To maximize abrasion resistance and strain relief, make sure that cable fittings for the flexible cable/portable cord
are the appropriate type and size for the cable/portable cord outer jacket diameter. Do not install the flexible
cable/portable cord in a manner that would place the cable in a bind or under excessive strain.
Grounding
The nature of Variable Frequency Drive systems must be considered prior to and during the installation of Big Ass
Fans. Due to high frequency content on the output side of the VFD, measures must be taken to ensure that all
grounding connections conform to the recommendations made in this section.
The VFD’s safety ground
must be connected to system ground. Ground impedance must conform to the
requirements of national and local industrial safety regulations and electrical codes. The integrity of all ground
connections should be periodically checked. All ground leads for downstream conduit boxes must be kept
separate from the motor ground and terminated on the VFD’s PE terminal.
Motor ground
The motor ground must be connected to a ground terminal on the VFD to aid in keeping high frequency electrical
noise o of the building’s ground grid.
Shielded motor cable terminations
Either of the safety ground terminals on the drive provides a grounding point for the motor cable shield. The motor
cable shield connected to one of the drive terminals must also be connected to the motor frame. If no drain lead
is present, the cable must be stripped back so that the braid can be twisted and soldered to a pigtail for proper
termination.
Input voltage irregularities
CAUTION: Controllers damaged by input voltage irregularities may not be covered by the your warranty!
The VFDs are suitable for direct connection to input power within the rated voltage of the VFD, but are sensitive
to rapid changes in supply voltage. The table shows input power conditions that may cause nuisance tripping
such as Overvoltage and Undervoltage faults. If any of the conditions exist as described, you can install one of
the devices listed under the heading “Corrective Action” on the input side of the VFD. One device is required for
each VFD!
Input Power Condition Corrective Action
Low line impedance (less than 1% reactance)
Install a line reactor. Contact Big Ass Solutions
Customer Service if you need to order a line
reactor.
Line has power factor correction capacitor
Line has frequent power interruptions (voltage sags or swells)
Line has intermittent noise spikes in excess of 6,000 V (lighting)
Phase-to-ground voltage exceeds 125% of normal line-to-line voltage
Install a Delta/Wye isolation transformer with
grounded secondary (1:1 turns ratio)
Ungrounded distribution system
Supply transformer exceeds established kVA limit
Install a line reactor
More than one controller, one per branch circuit
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