Rockwell Automation 7000L PowerFlex 7000 Medium Voltage AC Drive C Frame - Marine - Manual (Page 338)

A-4 Catalog Number Explanation – Drive Selection
7000L-UM302B-EN-P – June 2013 7000 “C” Frame - Marine
A tachometer is required under the following conditions:
1. When speed regulation accuracy must be between 0.01 – 0.02%
of nominal speed.
2. When the zero speed breakaway torque needed is greater than
90% of continuous running torque.
3. When continuous running speed is greater than or equal to 0.1
Hz, but less than 6 Hz.
4. For minimizing restart times using the flying start capability in
forward or reverse direction.
Power Flex Speed Regulation
Tachometer
Frequency Output
< 6 Hertz 6 – 15 Hertz Above 15 Hertz
Without Tachometer Not applicable 0.1 % 0.1 %
With Tachometer 0.02 % 0.01% 0.01%
Notes:
 Speed Regulation is based on % of motor synchronous speed.
 Tachometer to be mounted on the AC machine
 Operational 15 V DC Power Supply mounted in drive to power
the tachometer as a standard option with the tachometer feed
back card.
 Customer is responsible for providing and mounting of
tachometer
 Sleeve bearing motors require the tachometer to have an axial
movement tolerance.
 Recommended tachometers are shaft mounting type.
 Magneto resistive models are more adaptable to harsh
environments.
 When installing, the tachometer body and electronics must be
isolated from ground (options available from the tachometer
manufacturer to accomplish this).
 There are usually limits on tachometer cable lengths. Ensure the
maximum length is suitable for the application.
Tachometer Selection
Recommended Tach PPR
Motor RPM Tach ppr
3600 600
3000 600
1800 1024
1500 1024
1200 2048
1000 2048
900 2048
720 2048
600 2048
When is a tachometer
required?
When is a Tachometer
Required?