PWM in HVAC Chiller Controls - Pulse Width Modulation
Holden Shamburger
Chiller Training | Centrifugal Chillers | Screw Chillers
2 minute read
There are two ways to look at how we use PWM technology in HVAC.
You can see it from a controls or power perspective.
Today lets look at this from the controls side.
PWM = Pulse Width Modulation
This is the changing of an OFF to ON output signal in timed intervals.
Based on the time of signal OFF to ON an analog reference or command signal can be interpreted.
To keep a simple example let's use a 10 second duration period.
This means our controller is going to send and receive signals based on 10 second intervals.
If we want to have a 50% call then we will output our control voltage for 5 seconds and off for 5 seconds.
For a higher output then increase the ON time within the 10 second periods.
This can be used in many applications where we would use a 0-10vdc or 4-20ma signal.
I have worked on a lot of controls systems that blend all three signal methods depending on the specific device.
I would say that most will only combine 2 of these methods to fit the equipments needs.
MTT
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