The picture above is a motor performance curve for a 5 hp motor from Emerson’s U.S. Motors product line which you can obtain via their free MotorBoss website. Among other things, it shows how motor speed varies with the applied load. For those who want to see a better resolution version of the curves, I have them posted in the photo album on my CSE Magazine Google Account.
Some of you may remember that I have done several posts in the past that looked at the interactions between centrifugal machines like pumps and fans and the motors serving them. In particular, I have focused on how slip changes with load and how that can have an impact on the amount of energy a pump or fan might use when an existing motor is replaced with different motor with the same nominal speed but a different rated speed. I also shared an insight I had regarding a graphical technique that can be used to figure out the speed at which a given pump and motor combination will come into balance when they are operated together.
Now, thanks to the resources at the Pacific Energy Center, the generosity of Ryan Stroupe, who runs their Tool Lending Library program, co-presents a lot of technical training classes with me, and does a lot of training on his own, and the editing skills of Angelo De Stephano, another PEC staff member, I can bring all the mystery and excitement of a pump motor interaction to you via the spellbinding video clip that is inserted below.
Ryan and I created the video so we could demonstrate pump/motor interactions to a class of 80. Normally we take the students to the pump for this sort of activity, but the class size precluded this so we decided to experiment with a video approach.
In the video, I start out by familiarizing you with the system we are working on, which was the topic of discussion in the class immediately prior to the video. The pump system in question is the Chilled Glycol System used to cool the PEC. It’s an ice storage system that allows the facility’s peak electrical load to be shifted and also allowed the chiller to be downsized because on a peak day, it only needs to supplement the capacity stored as ice rather than meet the entire load on its own.
Here is a system diagram to give you an idea of what the system looks like.
In the video, I start out orienting you to the physical arrangement of the piping relative to the system diagram. Then I discuss some details of the system that have implications in terms of different commissioning functions and tasks. All of this builds towards the cliff hanger ending where we turn the pump on and I throttle the discharge while Ryan zooms in on the laser tachometer that is monitoring the pump speed. That starts about 3 minutes and 45 seconds or so into the video, and I’ll let you watch it rather than giving away the ending.
See you at the Oscars.
Senior Engineer – Facility Dynamics Engineering