Yaskawa F7 Drive 1500 Hz Output - Manual (Page 6)

Date: 05/05/05, Rev: 05-05 Page 6 of 7 TM.F7SW.056
6.0 Application Notes
6.1 Carrier Frequency
The carrier frequency should be left at 10kHz whenever possible. This is because at high output
frequencies, the number of output PWM pulses per AC sine wave cycle is low. At an output frequency of
1000Hz and a carrier frequency of 10kHz, there are only 10 output pulses per cycle. The fewer the number
of pulses, the less sinusoidal the current waveform will be. If the starting torque for the application is
insufficient with the default carrier frequency parameter settings, then use the following settings:
C6-03 = 10.0kHz Carrier Frequency Upper Limit
C6-04 = 1.0kHz Carrier Frequency Lower Limit
C6-05 = 24 Carrier Frequency Gain
6.2 Applying an Output Reactor
High-speed motors typically have very low impedance. This can result in excessive motor current,
increased motor temperature, low speed cogging, and increased torque ripple. The use of an output
reactor may be required to add impedance to the system. The output current should be measured using an
oscilloscope or chart recorder with a clamp-on amp meter to check for a sinusoidal waveform. If a reactor
is needed (based on the above mentioned conditions), be sure to account for the high output frequencies.
The reactor impedance is directly proportional to the output frequency and is usually given at 60Hz. The
same reactor operating at 1200Hz would have 20 times the impedance, which would result in 20 times the
voltage drop at rated load! Therefore, a reactor must be chosen that will smooth out the current waveform,
but not result in too large of a voltage drop. Unfortunately, there are no golden rules as to when a reactor is
needed or the correct amount of impedance of the reactor.
6.3 Current / Overload Ratings
In order to achieve a high carrier frequency across the entire model range, the F7 is operated in Normal
Duty 1. Normal Duty 1 is an unpublished operating mode that utilizes high carrier frequency, reduced
current ratings (same as Heavy Duty 1 ratings in TM.F7.01), and reduced overload (120% for 1 minute).
This software defaults the carrier frequency to 10.0kHz for all ratings to achieve the best possible current
waveform. In order to run the larger drives at 10.0kHz (models 2037 / 4075 and larger), the rated current is
automatically de-rated. The graph below details the de-rating of each model. The drive’s rated current for
10.0kHz operation is listed below in the table, which shows the de-rated values of the larger models. The
drive overload function (120% for 1 minute) uses the values listed in the table below as the 100% level.
The drive must be
correctly sized for the application using the correct overload and current ratings.
100%
80%
5kHz 10kHz 15kHz 0
Output current
derating factor
Carrier
frequency
F7U2030
F7U4030 ~ 4055
50%
8kHz
F7U2037 ~ 2090
F7U4075 ~ 4110
F7U4132
F7U4160
< F7U2022
< F7U4022
75%
De-rating of Rated Current Based on Carrier Frequency