Motor controll....

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JacksonburgFarmer

JacksonburgFarmer

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Location
Butler County Ohio
Have a customer who would like some motor controll work. Here is what they want. They have a 3ph 20hp motor running a grain blower, and a 2.5 hp motor running a auger that feeds the grain to the blower. They want to controll the speed of the 2.5 hp auger motor by the amperage of the 20 hp blower motor. Example, the 2.5 hp motor on auger runs faster untill the 20 hp on blower starts to get overloaded. Once Blower gets overloaded, the 2.5 hp is to slow down to alleviate load on 20 hp. I know that a VFD will have to controll the 2.5 hp speed, but what could i use off the 20hp to controll the VFD??? Supply house cant answer, trying to contact Square D, have yet to get answer.....So, what do yall thinK????? Thanks Ahead!!!!!!!:D
 
mdshunk said:
signal conditioner on a CT around the 20hp motor's leads. Signal conditioner's output into the 2.5hp's drive.
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I have used current transducers from NK Technologies for this task.
 
mdshunk said:
That's sorta a neat gadget. A CT with a signal conditioner built-in.
Click to expand...

They have several neat gadgets, especially the split core ones. Their tech and application support used to be very good (I haven't talked to them for 3yrs). I know that they brand label their devices to other companies.
 
PID Perhaps?

PID Perhaps?

I believe NK Technologies does a good job for both split and solid core. But there are several other products out there that can report your blower current via a 4-20mA signal to an auger VFD. Your choice if you want to pay a little more for split core though. A system this size is unlikely to use fixed bus. (When you may need to use split core to install). If the blower is on a VFD you need to be careful, some signal conditioners don’t like VFDS.

Your control scheme on the 2.5HP VFD could be PID control (proportional, integral, differential)

There would be three signal criteria for the VFD controlling the 2.5HP Auger:

• PV: Process variable. The signal proportional to the amperage from the Blower
• CV: Controlling variable: The Auger speed regulation to maintain a set point (next)
• SP: The set point (target) which would be the amperage you want to maintain on blower

PID is ubiquitous in control, it’s rather easy. It is similar to cruise control in your vehicle. PV is your speedometer, CV is your gas pedal and the SP is the speed you want to cruise at.

Most if not all VFDS on the market should have a PID control feature.

Alternatively, a VFD may be used on the blower in order to set a current limit if your feed rate drops off significantly for extended periods of time and you don’t want your blower running flat out unloaded and kicking up dust trying to achieve your set point. Of course then you could add a sleep function to the PID set up in the auger.
 
Last edited:
Can I quote myself?

Can I quote myself?

Last comment about sleep would be the auger also controlling the blower run and stop command, stopping the blower when it is not needed (sleep)
 
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