You’ve made one, I’ve made one too:  hand off auto circuits (HOA). HOA, or, perhaps more correctly, local-off-remote controls are common in the industrial landscape.  Offering a simple way to troubleshoot and commission, HOA circuits are frequently employed by engineers in control schemes. 

Saving time and money is always on my mind, and to help fellow engineers looking to do both, I offer a quick guide to HOA controls and PowerFlex drives.

The Nitty Gritty

OK, let’s dive in:

Setting a PowerFlex 750 Series up with an HOA

Setting a PowerFlex 525 up with an HOA

The above two links well explain how to program a variable frequency drive for an HOA circuit.  The built-in HOA start for the 750-series deserves attention. 

The “HOA Start” delays the high signal by a full cycle, allowing one digital input to be used as a start and stop.  Being able to create an HOA circuit with just one wire is the kind of convenience everyone is looking for. 

What the 520-series lacks in a dedicated HOA input, it more than makes up for in three start and speed references.  You can switch between sources by using a digital input or with programming through a PLC.  Either way, a 520 drive fits into an HOA circuit easily.

The Upshot

Ok, you might say, you can use a drive with an HOA.  Duh!  Don’t all drives do this? 

A good engineer can make anything work, but it is a question of how hard you want to work.  It is also about what you get along with the drive.  Allen-Bradley offers Connected Components Workbench (CCW) for drive and component configurations. 

Not only is CCW free, but its convenient wizards make drive setup a snap.  The feature I like most, though, is the ability to configure a drive while not connected.  This makes commissioning a breeze as you can have all your drive parameters already set up and ready for a download.

The Difference

Ease of configuration and installation economy are great features, but what really separates a PowerFlex drive from others is Premier Integration.  Having spoken much to the “H” in HOA up to this point, Premier Integration handily answers the “A” by allowing a VFD to seamlessly integrate into the Studio 5000 environment.  Integration means that drive parameters (like HOA start) can appear in Studio as tags with descriptive tag names with minimal work by a programmer.  Reductions in commissioning time of as much as 46% are possible when coupling a PowerFlex drive with an Allen-Bradley PLC. 

The HOA switch is tried and true.  Being able to save time in commissioning and troubleshooting adds value to an already convenient control method, and AB drives do this with built-in feature and Premier Integration.  Feel free to connect with me if you would like to know more and don’t forget to check out the main hep page for more drive information, tips, and tricks.

For more information about drives and drive systems, check out the Variable Frequency Drive Main Help Page