Let's unravel HVACR complexities with Tim R. Skell!
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At this moment, there are (3) different scenarios to consider:
- The fans are stopped.
- The fans are spinning roughly at the same speed.
- The fans are spinning, but at different speeds.
Scenario 1 is easy, as the motors are all stopped, most drives won’t have an issue here.
Scenario 2 is more challenging, but a quality VSD can catch the spinning motors and ramp them to the setpoint.
Scenario 3 is where we separate the basic VSDs from the advanced VSDs. I won’t get into the techy details, but a VSD essentially starts at the “average” speed from all those motors combined, and this results in a large current spike by the motors – which may result in a drive fault.
The ACH580 solves the challenges of Scenario 3 first by braking all the motors and then ramping them to the setpoint. For those interested in technical details, check out the related Technical Note.
