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9 - MOTOR CHARACTERISTICS
9.1.6 Power Factor Correction
DO NOT connect power factor correction capacitors or surge absorbers to the output of the VFD. Doing so may cause
damage to the VFD that is not covered under warranty.
If the VFD is used with a motor that is equipped with a capacitor for power factor correction, remove the capacitor
from the motor.
Connecting either of these devices to the output of the VFD may cause the VFD to malfunction and trip, or the output
may cause an over-current condition resulting in damage to the device or the VFD.
9.1.7 Light Load Conditions
When a motor is operated under a continuous light load (i.e., at a load of less than 50% of its rated capacity) or it VFDs
a load which produces a very small amount of inertia, it may become unstable and produce abnormal vibration or
trips because of an over-current condition. In such a case, the carrier frequency may be lowered to compensate for this
condition, see AFN 05-06 (Carrier Frequency Conguration).
9.1.8 Motor Load Combinations
When the VFD is used in combination with one of the following motors or loads, it may result in unstable operation.
A motor with a rated capacity that exceeds the motor capacity recommended for the VFD.•
An explosion-proof motor. •
When using the VFD with an explosion-proof motor or other special motor types, lower the carrier frequency to
stabilize the operation. DO NOT set the carrier frequency below 2.2kHz if operating the system in the vector control
mode.
If the motor that is coupled to a load has a large backlash or a reciprocating load, use one of the following •
procedures to stabilize its operation.
Adjust the Ramp Shape settings, •
Switch to the Constant Torque control mode. •
z NOTE: Consult motor manufacturer for operation on a VFD
9.1.9 Load Produced Negative Torque
When the VFD is combined with a load that produces negative torque, the over-voltage or over-current protective
function of the display may cause the VFD to trip.
To minimize the effects of negative torque a dynamic braking system may be used. The dynamic braking system uses a
braking resistor that must be suitably matched to the load.
The RSi S4 is equipped with a light-duty internal braking resistor which is sized appropriately for most applications. If
you require constant braking torque or faster stop times, a larger external braking resistor may be required.
9.1.10 Motor Braking
The motor may continue to rotate and coast to a stop after being shut off due to the inertia of the load. If an immediate
stop is required, a braking system should be used.
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