Lenze AC Tech SMVector Drive- More than Just Speed Control

December 17, 2013
ACTech SMVector Drive

ACTech SMVector Drive

At Holland, we have been specifying and putting sanitary pumps into high purity process systems for over 60 years. Every sanitary pump assembly has three major components: the pump, the base, and the motor. Previous posts have focused on all of those. With the advent of modern microelectronics, we often incorporate a fourth major component: the drive.

Modern variable frequency drives, or VFDs, use pulse width modulation (PWM) to convert 3 phase, AC electricity to DC and then they “chop” the DC up to trick the AC motor into thinking this is AC. DC enables us to control the frequency of current that gets to an AC induction motor. This allows us to vary the speed of a pump. While future posts will focus on selection considerations such as horsepower, amperage, and torque, this post will highlight a product our customers are getting a lot of use out of- the Lenze SMVector drive.

What makes the SMVector drive a great fit for the high purity applications we see with our customers all the time is the large number of options available for the drive. The drive is compact and available in NEMA 1, as well as NEMA 4X indoor and indoor/outdoor enclosures. The drive has 4 digital inputs (1 run/stop and 3 programmable), a Form A digital relay output switch, will accept both 0-10 VDC and 4-20 mA analog inputs, and will also supply a 0-10 VDC analog output. The drive also sports a 10 VDC potentiometer reference, a 12 VDC 20 mA power supply for digital inputs, and a 12 VDC 50 mA supply.

Other options for the SMVector drive include communications modules for DeviceNet, PROFIBUS, Ethernet/IP, and additional relay outputs. The drives can be ordered with a special terminal strip that incorporates a potentiometer and an option for a simple, 4 wire remote keypad (and yes, we can supply the remotes with NEMA 4X enclosures).

VFD Pumps

VFD Pumps

Ok, that’s great, but any VFD can do that, what other capabilities does the SMVector drive have? With the SMVector drive, not only can you start, stop, speed up, slow down, and change the direction of your motor, you can also unlock several other possibilities. The first applied application we’ll discuss is PID loop control.

While PID loop control can be complex, many applications we see are relatively simple, such as using a pressure transducer to maintain constant pressure to a spray nozzle. In a PID system there are two signals required: a system set point and a system feedback. The set point tells the system what pressure should be maintained. The feedback signal tells the controller (in this case the SMVector drive) what the actual system pressure is. The drive then compares these two signals and adjusts the speed of the motor. A system like this is a “normal” acting system. As feedback increases (pressure goes up), we want the motor to slow down. And as feedback decreases, we want the motor to speed up. After some simple programming steps and tuning, the drive can be used to control the PSI of the line feeding the nozzles. Specific wiring and parameter setting are outside the scope of this blog, but contact Holland today for additional help.

The second relatively simple application we see where customers could leverage the power of the SMVector drive is with fill bowl speed control. Limit switches in a filler feed bowl can be used to “sequence” preset speeds on the drive and allow for a gradual, controlled filled that helps limit overshoot. For example, let us consider a filler bowl with 3 level switches.

When the fill begins, the drive is simply turned on at 60 Hz to move product from the hold tank to the fill bowl. When the 1st limit switch is reached, the switch sends a signal to the drive to begin sequencer segment 1. Let’s pretend this decreases the speed to 47 Hz for 5 seconds (or until limit switch 2 is reached). When limit switch two is reached, sequencer segment 2 begins, and speed is decreased to 30 Hz for 5 seconds (or until the 3rd limit switch is reached). When the 3rd limit switch is reached, the speed will be again reduced, to 15 Hz, for ten seconds. After sequence three, the drive will stop.

The sequencer segment speeds and times have a wide range of adjustment and can be optimized for variety of applications. Again, contact Holland today for additional wiring and parameter setting guidance.

To conclude, sanitary pumps are not often run at just one speed anymore. Pumps today are often sized for multiple duties, speeds, and products. In order to get the most versatility out of your sanitary pump, a variable frequency drive is essential. Not only do they offer start/stop, speed control, and potential energy savings, the Lenze AC Tech SMVector drive can be used in place of third party PID loop and batch controllers to accomplish all of these things in one simple package. Contact Holland today for specifying your next drive.