10.13 Using The Pwm Instruction For Motor Control - Mitsubishi FX1S Series Programming Manual

FX Series Programmable Controllers

10.13 Using The PWM Instruction For Motor Control

The PWM instruction may be used directly with an inverter to drive a motor. If this configuration
is used the following ripple circuit will be required between the PLC's PWM output and the
inverters input terminals.
Circuit configuration for a PLC with source outputs
Key to component values:
R1 - 510 Ω (1/2 W)
R3 to R8 - 1kΩ (1/4 W)
R10 - variable dependent on configuration. In this example 1kΩ (1 W)
C1 - 470 µF
Note: the values of R10 and C1 are dependent on the system configuration.
Establishing system parameters and values
It is assumed that the input impedance of the inverter is of a high order. Having established
this, the values of C1 and R10 are calculated to give τ a time result (in msec) approximately 10
times bigger than the value used for T
τ = R10 (kΩ) ÅL C1 (µF)
During this calculation the value of R10 must be vastly greater than the value of R9. In the
example, R9 is equal to 22Ω, where as R10 is equal to 1kΩ. This proportion is approximately
1:50 in favor of R10.
R2 - 3.3kΩ (1/2 W)
R9 - 22 Ω (1/4 W)
in the PWM instruction:
0
Points Of Technique 10
FX FX FX
1S 1N 2N
10-15
FX
2NC