CT input for CompactLogix?

[CanaanP 1]

I need to bring the signal from several CT's into a PLC to monitor amp draw on several soft starts for an upcoming project. Is it necessary for me to go through a signal conditioner of some type, then to a analog input for PLC, or is there a card that accepts a signal directly from CT's?

[Mickey 71]

I don't believe there is a module for that. AB does make a "Power Monitor", but I would go with something like this. See links below. http://www.loadcontrols.com/products/products.html https://www.ohiosemitronics.com/ Edited 20 Feb 2010 by Mickey

[Ken Roach 194]

Current Transformer always go through a transducer, usually with 4-20 mA output, before going into a controller. There are three of them humming along behind me connected to a 1756-IF16 right now. If you just want to monitor current, ordinary CT's and transducers are the way to go. I like the PowerMonitor 3000 and 1000 (for small and simple jobs) for actually measuring power and power quality.

[paulengr 44]

There are CT's with a 4-20mA converter on board. You can even buy then through McMaster-Carr (next day delivery). For conversion for a non 4-20mA unit I usually stick a Simpson meter with a redirected 4-20mA output in the panel. This gives you both local readings and 4-20mA for about the same cost as just a transmitter.

[ElecPneuGuy 1]

Use SMC Flex soft starts with Ethernet. The SMC Flex will give you the current. Other parameters are available too.

[paulengr 44]

Really? Every time I run the cost numbers on those, I end up going with an outright drive. Soft starts are usually more expensive these days. There are exceptions. In medium voltage, a Benshaw softstart is less expensive than a drive, but then we're talking about the world >500 HP. If you are angling in that direction, there's the E1{lus and E3Plus overload relays. You are stuck with DeviceNet but where these really come into their own is with an entire MCC full of them with an EN2DN attached to the end of the DeviceNet chain. The 100-DNY modules serve a similar though much more limited purpose. Without the DeviceNet stuff, the E1-Plus electronic overload relays are less expensive than a eutectic overload relay module and give you better protection. There is a DeviceNet adapter card that attaches to the side of the basic overload relay. The DNY modules are general purpose and have something like a couple output relays, a couple inputs, and I believe some analog along with DeviceLogix for local control functions. The E3Plus combines all of this together and makes it so that you don't need ANY control wiring in the starter enclosure at all except for perhaps if you need some kind of hard wired safety interlocks. If you order an "Intellicenter" MCC, it comes with E3Plus's loaded in each bucket. You can get an "Intellicenter" as a medium voltage lineup or even as switchgear. The primary difference is that frequently it may have 801P's instead of E3Plus's for some applications but even over a certain HP rating, the E3Plus becomes a generic external module reading a set of CT's. Note that I'm NOT a DeviceNet fan except in this one case and it's really a question of necessity (not available as Ethernet/IP).