PowerFlex 753 Digital Input - current rating

[izadi]

Hello everybody,

I am connecting my DCS digital output (115VAC) to AB PowerFlex 753 Digital Input. We are using the 20-750-2262D-2R I/O option in the powerflex which is 115VAC I/O with 2 Analog In, 2 Analog Out, 6 Digital In and 2 Relay Outputs.

My question is, what is the current or power consumption of the PowerFlex DIs at 115VAC. I need to specify the right fuse size for my digital output.

Thanks,

 

[dmargineau]

Starting at page 255 of:

http://literature.rockwellautomation.com/idc/groups/literature/documents/in/750-in001_-en-p.pdf

 

[izadi]

Thanks dmargineau,
But the current rating is only specified for the DO's (page 256) but not for the DI's (page 255).

 

[danatomega]

The inputs can't draw much more than 5 - 20 mA, maybe 50 at the most.

 

[dmargineau]

Page 260...

 

[izadi]

danatomega,

That's what I suspected but what is the science behind it? Is it correct if I assume internal resistance for DI's are designed to be high?

 

[danatomega]

You have optical isolation on input - that's usually high impedance.
The manual says this about the inputs:

24V DC (30V DC Max.) - Opto isolated
High State: 20…24V DC 11.2 mA DC
Low State: 0…5V DC​

120V AC (132V AC Max.) 50/60 Hz

(4) - Opto isolated

High State: 100…132V AC​

Low State: 0…30V AC
So, I can't imagine ​

the 120VAC using too much more current - the manual doesn't bother stating the actual draw.
​

 

[jraef]

All they will "draw" is going to be the power to fire up the little opto isolator inside. As consumption goes, it is considered insignificant on the 115VAC inputs, which is probably why they don't bother with the info.

It's 11.2mA at 25VDC on the DC inputs, I can't imagine it's any more than that on the AC inputs as well, the circuit inside is basically the same. Download the Reference Manual, 750-rm002, look on page 102 and it shows the basic internal circuit, with it being the same whether it is DC or AC. So it's only the opto itself that differs between them.

So you are looking at MAYBE 1W for each input at 120VAC.

 

[izadi]

Thanks so much every body.