Torque vs Amps 2

[rybrk]

I want to measure the torque of motor when more load applied on the impeller of motor(application:Rapid mixer granulatot)to determine the %end point for wet granulatin process.is there any source to get torque meter with sensor.
presently iam measuring amps by using ammeter and calculating manuually % end point of RMG.Is it acceptable?

thanks

rybrk

 

[ScottyUK]

Your ammeter will measure magnetising (reactive) current as well as current delivering power to the motor. You can install a cheap power transducer with a single phase VT and CT input which will give the active power input per phase. Assuming the motor is (more-or-less) constant speed such as a standard induction or synchronous machine this will give you a reasonable indication of torque. You could obviously fit a three-phase meter, but as this device is intended to imply torque the additional complexity is probably not worth the effort.


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Sometimes I only open my mouth to swap feet...

 

[Skogsgurra]

If it is a DC motor, your strategy is right. If it is an induction motor, you have the problem mentioned by Scotty.

You can also use a frequency inverter to feed the motor. Vector controlled inverters have an output signal (or can display) the true torque.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[jraef]

The other problem you have trying to measure load by using amps only is that if voltage varies, the current will vary irrespective of the load. The way around that is to measure kW (power) as ScottyUK mentioned, which follows load regardless of voltage fluctuations. There are "Load Monitor Relays" available on the market that do this. A good one I have used is made by Emotron, based in Sweden but available worldwide, which claims to actually calculate shaft torque based on kW and power factor. I have found it to be a very accurate torque sensor. Emotron M20 link. Another is Load Controls Inc. based in the US, although haven't used that one personally. Load Controls Inc. link

JRaef.com
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