Hitachi MLFC wire

[Mayfran]

I was setting up a chip conveyor speed control and was going to use a current tranbsducer on the spindle drive AC input as my speed reference. As the spindle drew more current (cutting deeper and making more chips) the chip conveyor speed would increase. However I cannot get a current read with an AC current transducer, or my Fluke meter through this MLFC wire. I have not found anything on the wire that indicates it is shielded to prevent emf noise. Does anyone have any experience with this wire and if so, similar conditions?

 

[ScottyUK]

Does the drive not provide an analogue output signal proportional to speed? That seems the most obvious solution.


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If we learn from our mistakes I'm getting a great education!

 

[Mayfran]

We're looking for something generic and inexpensive that we can install on any OEM CNC machine without having to engineer for each make and model. Using the current transducer and having the customer clamp it on the motor / drive input lead seems like the simplest way. I agree the drive output would work, but the engineering hours would not make it cost effective.

Jim

 

[itsmoked]

Is the spindle powered thru a VFD? If so you can probably get the VFD to put out either a speed signal, a current signal, or a %of-something-that-will-work signal you can use. This signal could directly drive the speed input on the chip removal VFD - if you're using one.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[davidbeach]

Sensing between the motor and the drive is going to give you so much noise that you may never get a good reading and the type of wire has nothing to do with it.

 

[Mayfran]

I am trying to read BEFORE the drive(read my first sentence), shoot I tried to get a read off of the main CB and did not get anything on the amp clamp except the normal small amount of noise. I tried 3 clamps, so that is not the problem. And when I went on non MLFC wire I did get reading on other circuits (control voltage etc).

I'm asking if anyone has used this wire and if so, did you experience similar conditions??

 

[DRWeig]

Hi Mayfran,

Should be no problem -- Hitachi's own MLFC brochure (see download) shows it going through conventional CTs. It's not shielded.

Good on ya,

Goober Dave

 

[ScottyUK]

Nothing in the MLFC cable makeup suggests it would have any screening or similar effects - it looks like a conventional high flexibility single-core cable laid up in the manner of a wire rope. I think you're looking for a cable effect which isn't there, or at least one which the accepted laws of physics say shouldn't be there. I've not used that specific cable but I have used one with remarkably similar construction from Hubert & Suhner. Funnily enough we actually had the H&S cable fed through a couple of cheap LEM Hall-effect transducers and other than the capacitive noise coupling problem which seems to affect most cheap LEMs when installed on high dv/dt conductors everything behaved just like we expected.

Aside from the possibly magical properties of the MLFC cable, measuring the harmonic-laden input current isn't going to give you a terribly accurate indication of the input power, although there will certainly be a relationship.


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If we learn from our mistakes I'm getting a great education!