Specifications

Altivar
®
31 Adjustable Speed AC Drives
Functions
37
4/2005
© 2004–2005 Schneider Electric All Rights Reserved
Switching frequency, noise reduction
The setting of the switching frequency permits a reduction in the noise
generated by the motor.
The switching frequency is modulated randomly to avoid resonance. This
function can be disabled if it causes instability.
Switching the intermediate DC voltage at high frequency is useful for
supplying the motor with a current wave having little harmonic distortion. The
switching frequency is adjustable during operation to reduce the noise
generated by the motor.
The value ranges from 2 to 16 kHz, with a factory setting of 4 kHz.
This function is suited to all applications requiring low motor noise.
Skip frequencies
This function suppresses one or two critical speeds that may cause
mechanical resonance. It prohibits the prolonged operation of the motor on
one or two frequency bands (with a bandwidth of ± 1 Hz), adjustable within
the operating range.
This function is suited to lightweight machines, bulk product conveyors with
an unbalanced motor, fans, and centrifugal pumps.
Speed reference
The speed reference can come from the following sources, depending on the
drive configuration:
• the three analog inputs
• the potentiometer (for ATV31••••••A drives only)
• the logic inputs, using the +/- Speed function
• the drive local keypad display or remote keypad display
• the communication networks
These different sources are managed by programming the reference
functions and channels.
Analog inputs
There are three analog inputs:
• Two voltage inputs
— 0 to 10 V (AI1)
— ± 10 V (AI2)
• One current input
— X–Y mA (AI3) where X is configurable between 0 and 20 mA, and Y is
configurable between 4 and 20 mA.
2 Hz
Motor speed change depending
on the skip frequency reference
Reference
f (Hz)
563538
Courtesy of Steven Engineering, Inc.-230 Ryan Way, South San Francisco, CA 94080-6370-Main Office: [phone]-Outside Local Area: [phone]-www.stevenengineering.com