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Geo Direct PWM Amplifier

PWM Frequency 36

PWM FREQUENCY

The minimum PWM frequency of a system is based on the time constant of the motor. In general, the

lower the time constant, the higher the PWM frequency should be. The motor time constant is calculated

dividing the motor inductance by the resistance (phase-phase). The minimum PWM Frequency is then

determined using the following relationship:















;





























Example: A motor with an inductance of 6.1 millihenries (mH), and a resistance of 11.50 Ohms (

phase-phase) yields a time constant of 0.53 milliseconds. Therefore, the minimum PWM Frequency is

about ~6000Hz (6.0 KHz).

Note

Systems with very low time constants (needing higher PWM

frequencies) may require the addition of chokes or in-line inductive

loads to obtain a good current loop bandwidth.

Note

The maximum PWM frequency for each model of the Geo Direct

PWM Drives is listed in the electrical specifications.

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Delta Tau Geo Direct PWM Amplifier Manuale di Installazione Pagina 36