MicroMaster 440. Can it detect phase loss or phase unbalance ?

JesperMP · Mar 3, 2006

Hi,

I have an application where I have to change a vibratory conveyor from DOL start to VFD.
Normally I use a set of current-sensing relays to detect phase loss.
Will it be possible to let the MM440 detect phase loss (on the load not the supply side !) or even better phase unbalance (because there are two motors running in parallel) ?

I ask here because there are so many parameters to tinker with, and maybe someone knows allready, and I am lazy by nature.

PLucas · Mar 3, 2006

Jesper,

Is this what you are after?

I had to shrink the image down to get it upload.

Paul

JesperMP · Mar 3, 2006

Unfortunately Paul, it says fase loss on the input side.
I need detection of phase loss or unbalance on the output side - in case a wire has come loose in one of the motors.
So it wont help me.
Thanks anyway

PLucas · Mar 3, 2006

JesperMP said:
Will it be possible to let the MM440 detect phase loss (on the load not the supply side !) or even better phase unbalance (because there are two motors running in parallel) ?

Doh!

Sorry Jesper,

While I was reading your post, I got disturbed by some prat walking into my office and asking questions about work related stuff, then I replied to your post without re-reading it to confirm what you were actually after!

Next time I'll keep my office door shut.

Paul

Andybr · Mar 3, 2006

Jesper.

We have quite a number of vibratory conveyors with dual motors on VFD's and they were plagued by problems when they were first installed. When you set up your drive be very careful about ramp rates and the stopping mode. The "as installed" set up for our systems used default settings for the VFD's which ramped the frequency to 0 when the conveyors were stopped. This allowed the weights on the drives to come to rest slightly out of synch with each other which caused severe stability problems when the conveyor was restarted. We solved the problem by selecting "coast to stop" on our VFD's and using the quickest acceleration ramp we could get away with. The conveyors are designed to run at a specific frequency and do not normally behave well as they are ramped up to speed.

JesperMP · Mar 3, 2006

Thanks for the advice Andy.

The conveyor manufacturer has OK'ed to use a VFD.
The idea is to let the conveyor run at a low speed that doesnt transport material, and then run at nominal speed when transport of the material is required.
In that way a fast start and stop is achieved - of the material, not the conveyor.

Andybr · Mar 3, 2006

Jesper
Is this a Key Isoflow conveyor. We have systems which work like this and they work well once they have been fine tuned after installation.

10baseT · Mar 3, 2006

Like Andy , we suffered many huge problems with using a 440 on Cobra conveyors with contra rotating balance weights , as you may know , when these drives are run DOL , it is generally considered good practice to stop them by bumping them briefly into reverse , which stops nasty low speed oscillations .

Many problems with I2T tripping after some hours of operation , set up was a real pain .
We ended up with an 8" square box section in two bits using one of these things !

I would NEVER start any vibe , whether balance beam , contra rotating rotor , or spring beam type with product on it - of all the equipment in the place , vibes are always allowed to discharge onto a band before being stopped .

JesperMP · Mar 3, 2006

Andybr said:
Is this a Key Isoflow conveyor. We have systems which work like this and they work well once they have been fine tuned after installation.

No, it is a regular vibr. conv. with counter-rotating weights but from a company that makes many kinds of such conveyors. So I trust that they know what they are talking about.

10baseT said:
Like Andy , we suffered many huge problems with using a 440 on Cobra conveyors with contra rotating balance weights , as you may know , when these drives are run DOL , it is generally considered good practice to stop them by bumping them briefly into reverse , which stops nasty low speed oscillations .

Yeah, I know how they oscillate when running through the low frequencies. However we dont intend to stop the conveyor completely, only to reduce the speed so much that the material doesnt move. I think that we only have to reduce the speed 10-15% to achieve that. The weights are allready adjusted to achieve the slowest movement allready.

10baseT said:
I would NEVER start any vibe , whether balance beam , contra rotating rotor , or spring beam type with product on it - of all the equipment in the place , vibes are always allowed to discharge onto a band before being stopped.

Normally we also discharge these conveyors completely before stopping, but the manufacturer has OK'ed the whole thing. And it must be possible to do it as Andy has such a working conv. allready.

It has allready been decided upon. I am just trying to figure out if I can save the current monitoring relays.

DickDV · Mar 3, 2006

I'm quite sure that the current balance relays will not measure current properly and therefore will not detect imbalance properly either. It may detect complete phase loss, I would test it to be sure.

Depending on the drive you choose, some are very good at phase imbalance and phase loss faulting. You will need to read the fine print in the instruction manual to be sure.

DickDV · Mar 3, 2006

Just an afterthought--if you find that the relays will not detect imbalance but will detect complete loss, buy an extra one so you have one for each motor branch and use them that way.

I wouldn't worry too much about detecting phase imbalance. Whether the motor or the drive is causing the imbalance, neither will likely go on for long before other problems develop and drive fault will occur for these other reasons. (I'm assuming that the brand of drive you've got has at least minimal intelligence---and no, I will not name brands!)

scottmurphy · Mar 4, 2006

Please correct me if I have read this wrong, but could you not use an overload for each motor, on the output side of the drive? This will detect phase loss and imbalance?

I have seen setups like this before where 2 motors are run off one drive, and seems to work fine.

Richard Christian · Mar 4, 2006

The MM440 will automatically pick up a lost phase on the output.
Running vibes at and speed 10% up or down on design speed will normally result in mechanical problems. If you run at low speed this is not too much of a problem but if the vibe has product or load on it, it will not balance with the mass of the counter balance weight. As an aside, the MM440 can be a bit of problem with Cobras because of the two motors, the MM440 will start by reading the stator resistance, having two motors connected stuffs this up a bit. It can all be programmed out.. but as there are what seems to be a million parameters it can be a nightmare to get it wrong.. which I have in the past and destructed 4x4 box section supporting the motors.

Fred Raud · Mar 4, 2006

scottmurphy said:
Please correct me if I have read this wrong, but could you not use an overload for each motor, on the output side of the drive? This will detect phase loss and imbalance?

I have seen setups like this before where 2 motors are run off one drive, and seems to work fine.

i was kind of thinking what i think you thinking scottmurphy,,that the vfd should detect phase loss very fast,,im not sure what special implications having it drive a vibrator,,im going off the answers given to me in my thread about current draw and frequency on a vfd,,others had said i can direct drive a motor with my vfd with no need of over load protections as it would be redundant,,(vfd would handle it easy),,maybe im missing part of the picture here,,

Fred Raud

10baseT · Mar 5, 2006

The 440 didn't discover the imbalance on THAT Cobra Richard !!

as you quite rightly state , it ended up with a big crack - though not all entirely attributable to the drive .

that drive tripped out on I2T , and if you remember , the only way to get the thing running was a full factory reset , and reprogram , the parameters were so far away from where they should have been (after welding back in a big lump of box section)

Do you remember what the intermittent fault was ?

MicroMaster 440. Can it detect phase loss or phase unbalance ?

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