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6 Application Notes
6
Application Notes
Using an Output Reactor
If drive oL2 faults occur and a typical drive overload is not suspected, an output reactor or a
larger drive may be required to eliminate oL2 faults. High-speed motors typically have very
low impedance, which may result in excessive peak motor current, increased motor
temperature, low speed cogging, or increased torque ripple.
It may be necessary to use an output reactor to add impedance to the system and reduce the
peak ripple current and eliminate nuisance oL2 faults. To confirm that excessive peak
current caused by low motor impedance is causing the oL2 fault, measure the output current
using an oscilloscope or chart recorder with a clamp-on amp meter.
Generally, the peak of the motor current waveform should not exceed 100% continuous
drive HD nameplate x 2.5. This value may vary slightly by drive model. Refer to
Figure 4
for an example of peak current measurement.
When using a reactor to reduce peak current, consult with the reactor manufacturer to select
a reactor that will smooth out the current waveform and also prevent a large voltage drop.
Proper reactor selection is critical in high speed applications because the reactor impedance
is directly proportional to the output frequency, which is usually given at 60 Hz. Example; a
reactor operating at 600 Hz will have 10 times the impedance and result in 10 times the
voltage drop when compared to the same reactor operating at 60 Hz.
Using a larger capacity drive to allow for the additional peak current may also solve the oL2
overload trip problem. The decision to employ an output reactor or increase drive capacity is
made on a case-by-case basis.
Figure 4
Figure 4 Measuring Peak Current
16
YASKAWA ELECTRIC TM.V1000SW.134A 1000 Hz High Frequency Custom Software Supplement
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