Motor and Control Applications: Total Cost Counts

When designing a motor and control application, how often do we actually take the total cost of ownership into account? Are we “saving money” by cutting corners on conductor sizes, ignoring voltage drop and imbalance in our designs? Are we sizing wires incorrectly? The real answer is we probably don’t think about total cost of ownership often enough. We are usually faced with many constraints such as:

1. Time: rapidly encroaching deadlines.
2. Multiple projects on deck.
3. Numerous other distractions that we face each and every day.
4. Space available for components.

There was recent article on the Electrical, Construction and Maintenance website about some energy saving tips for motor installations. I shared this with my colleagues and received some interesting feedback about motor and control applications. It’s a good read, so check it out if you get a chance.

One of our controls guys said, “I hadn’t thought of conductor size before from a cost savings over time. I usually push back on customers over sizing wire more than they have too. It effects our input breaker lugs being large enough.”

One of our branch managers commented, “Good Read.  Never even thought of voltage drop because of mis-sized wires!”

We all know the basic formula for Ohm’s Law E=I/R.  But how does that apply in this situation? The smaller the conductor the higher the resistance and therefore higher current. Higher current results in more electricity needed to perform the same amount of work.  As an Electrician and Maintenance Mgr. in my former occupations, I always focused on this aspect of new motor and control applications. I was usually able to get approvals by showing that by spending a little more on the front end we could save a lot more on the back end. That cost savings was essential to getting my projects approved.

We all know about using energy efficient motors but most of us don’t even think about conductor sizing, voltage drop, or imbalance. These also play important parts in the total cost of ownership. We try to point this out to customers we are working with, since a lower total cost of ownership = a lower bid on many projects.

Dave Oliver grows very, very hot ghost peppers and is a field service technician for Innovative-IDM’s Memphis branch. You can reach him at [email protected]