Seco DS9000 Installation & Operation Manual page 34

1. Calculate the maximum input frequency of the reference signal.
(Maximum RPM) (Pulses per revolution) (1 min. ) = Max. Freq. (Hz)
Example 1
Example 2
Now that you know the maximum frequency of the input, calculate the requirements for the follower
system.
(Max output speed) (PPR of feedback device) (1 min.) = Max Freq. (Hz)
Example 3
Example 4
Now that you have calculated the maximum reference frequency and the maximum feedback for the
follower, we can calculate the ratio values that would be programmed in PS1, PS2, PS3 or PS4.
Ratio calculation #1
Let's use the reference in example 1 and the follower in example 3. The equation to use is as follows.
% of follower maximum = Ratio
% of reference maximum
The simplicity of this is that you can use whatever units you want, Frequency, RPM, Feet per Minute
or whatever engineering units you would like to use. The units have to be a percentage of whatever
they are at the maximum frequency you calculated, as in examples 1-4.
To show this, let's work out two different ratios using example 1 for the reference and example 3 for
the follower.
Master = 1800 Hz max. input frequency @ 1800 RPM
Follower = 1125 RPM @ 2250 Hz max. feedback frequency
For the benefit of this example, the master and follower are both conveyor belts, master top speed is
300 feet per minute and the follower is geared to run maximum of 200 feet per minute.
If the follower motor is to run at 200 RPM when the master is running at 300 FPM, what is the ratio?
We can solve this in three different ways. We can use percentages of frequency (Hz), motor speed
(RPM) or line speed of the conveyor (FPM).
200 FPM
% Follower 200 FPM
_________= _________
300 FPM
% Reference 300 FPM
Since we are looking at the percentages of the follower to the master reference, the units we use do
not change the correct ratio value.
Now, we want the follower to run at 120 FPM when the master is running at 225 RPM. What is the
ratio?
(60 sec.)
(1800 RPM) (60 PPR) (1 min.) = 1800 Hz
(60 sec.)
(1500 RPM) (120 PPR) (1 min.) = 3000 Hz
(60 sec.)
(1125 RPM) (120 PPR) (1 min.) = 2250 Hz
(1800 RPM) (60 PPR) (1 min.) = 1800 Hz
(60 sec.)
1125 RPM
1125 RPM
= _________
1800 RPM
1800 RPM
(60 sec.)
(60 sec.)
2250 Hz
2250 Hz
= ________
1800 Hz
1800 Hz
1
= ___ = 1.0
1
33