2017 NEC Chapter 9 Tables 11A_B

[CRW_BOCES]

What condition/Equipment would use DC interrupted at 10 to 200hz?
And what duty cycle?
Any help would be greatly appreciated!

 

[LarryFine]

Welcome to the forum.

I'm confused: how can DC have a frequency range?

 

[don_resqcapt19]

I think the OP is talking about Chapter 9, Table 11B, and not something in Article 430.

There are pulsed dc systems and Note 4 would refer to those types of systems.
One old example was something they used a long time ago for car radio. The used "vibrator" that changed the steady state 6 volt dc so they could use a transformer to increase the voltage. Higher voltages were needed to operate the radio.

Not sure what would used pulsed dc now.

 

[CRW_BOCES]

@don, yes, the Chapter 9, table 11 A/B note section. Never though about the vibrator power supply for a tube radio, probably only a few left in hands of collectors. Thanks for the memory jog!

 

[CRW_BOCES]

Welcome to the forum.

I'm confused: how can DC have a frequency range?

It is the on/off frequency of a DC source. I can easily visualize the waveform, but applications are what I am trying to come up with for my apprentice class students.