# Setting Of The Electronic Gear (pr. 420, Pr. 421, Pr. 424) - Mitsubishi Electric FR-A720-0.4K Instruction Manual

Fr-a700 series.

4.6.4

## Setting of the electronic gear (Pr. 420, Pr. 421, Pr. 424)

Set the ratio of the machine side gear and the motor side gear.
Parameter
Name
Number
Command pulse scaling
420
factor numerator
Command pulse scaling
421
factor denominator
Position command
424
acceleration/deceleration
time constant
The above parameters can be set when the FR-A7AP (option) is mounted.
*
When the operation panel (FR-DU07) is used, the maximum setting is 9999. When a parameter unit is used, up to the maximum value within
the setting range can be set.
(1) Calculation of the gear ratio (Pr. 420, Pr. 421)
⋅ The position resolution (travel per pulse Δ
feedback pulses Pf [pulse/rev] of the detector, and is represented by the following expression.
Δ :travel per pulse [mm]
Δs
Δs: travel per motor rotation [mm]
Δ
=
Pf
Pf: number of feedback pulses [pulse/rev] (number of pulses after multiplying the number of
Using the parameters, the travel per command pulse can be set separately to set the travel per command pulse
without a fraction.
Δs
Pr. 420
×
Δ
=
Pf
Pr. 421
In addition, the relationship between the motor speed and internal command pulse frequency is as follows:
Pr. 420
×
= Pf ×
fo
Pr. 421
CAUTION
Set the electronic gear in the range of 1/50 to 20.
Note that too small a value will decrease the speed command and too large a value will increase the speed ripples.
[Setting example 1]
The electronic gear ratio is Δs = 10 (mm) when the travel per pulse Δ
pulses Pf = 4000 (pulse/rev) in a drive system where the ballscrew pitch PB = 10 (mm) and the reduction ratio 1/n = 1.
According to the following expression,
Δ
Pr. 420
Pr. 421
Therefore, set "4" in Pr. 420 and "1" in Pr. 421 .
[Setting example 2]
Find the internal command pulse frequency of the dedicated motor rated speed.
Note that the command pulse scaling factor Pr. 420/Pr. 421 = 1.
Assuming that the number of encoder pulses is 2048 (pulses/rev) (feedback pulse Pf = 2048 × 4),
fo
Therefore, the internal command pulse frequency is 204800 (pps).
Initial Value
1
1
0s
[mm]) is determined by the travel per motor revolution Δs [mm] and the
No
fo : Internal command pulse frequency [pps]
Motor speed [r/min]
60
No :
Δs
Pr. 420
×
=
Pf
Pr. 421
Pf
×
= Δ
Δs
4000
4
= 0.01 ×
=
10
1
4
= 2048 ×
(multiplication)
= 204800
Position control by vector control
Setting
Range
0 to 32767 *
Set the electric gear.
Pr. 420 is a numerator and Pr. 421 is a denominator.
0 to 32767 *
Used when rotation has become unsmooth at a
0 to 50s
large electronic gear ratio (about 10 times or more)
and low speed.
encoder pulses by four)
= 0.01 (mm) and the number of feedback
No
Pr. 421
×
×
60
Pr. 420
Vector
Vector
Vector
Description
135
4  