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AMC1304M25: Insulation according to IEC61800-5-1

Guillaume Leray
Prodigy 10 points
Part Number: AMC1304M25

Tool/software:

Hello Team,

We are currently working on the development of a brushless motor controller which must comply with IEC61800-5-1. (3ph 400Vac input)

Our product notably contains an AMC1304 for measuring current on the motor phases.

Ti has an interesting and detailed note on insulation according to 61800: "Isolation in AC Motor Drives:Understanding the IEC61800-5-1 Safety Standard" (slyy080a).

However, the determination of one parameter is not clear to us: the “Working Voltage” (page 7 of the note). This parameter is necessary for creepage constraints.

"Several factors complicate the computation of the working voltage. First, the high-frequency trapezoidal PWM modulation on the inverter output can change the RMS of the working voltage for the isolated gate drivers and isolated sense elements. Second, increasing DC bus voltage during motor braking can mean occasional higher voltage across the insulators. Therefore, determine the working voltage of every isolator carefully."

Would TI have examples of calculations for determining these system parameter? Or is this measured only on the system??

Thanking you in advance for your help,

Sincerely,

Guillaume Leray

  • 0
    TI__Guru 55342 points

    Hi Guillaume,

    I believe these parameters would change system to system as it would depend on design and operation of the users system. However, I do think it is important to consider calculating the highest RMS or DC value that the device may see for an extender period of time, both in normal operation as well as a failure mode when calculating necessary working and isolation voltages.