S120 speed fluctuation

Hello,

I'm having a weird problem.

We have a reactor stirrer (4kW, 1500rpm) attached to a drive set in U/f control.

When setting a low rpm (max 25 rpm) everything is normal. When I go higher the speed starts to fluctuate (going from +150 to -150). The stirrer itself is fluctuating as well, but only in positive direction.

When I follow the setpoint, everything is normal to r1119, not anymore from r1150.

The problem remains when I bypass the ramp generator.

Motor resistance is OK, the gearbox and bearings as well.

The power module has been replaced, problem remains.

CU310 DP: 6SL3040-0LA00-0AA0

PM340: 6SL3210-1SE21-0AA0

Can the CU be the problem, this hasn't been changed?

Thanks,

Mike

 Hi Mike,

MikeGoeman

The stirrer itself is fluctuating as well, but only in positive direction.

I have not got if there's stirrer own fluctuation at low speed and if there's stirrer own fluctuation at high speed.

MikeGoeman

"Only positive direction"

 What does it mean? Cannot imagine mixer fluctuation "only in positive direction, negative, all directions",

Also, mixer own fluctuation, what's really fluctuates in mixer? What do you mean by that?

Msorich

Msorich

 Hi Mike,

MikeGoeman

The stirrer itself is fluctuating as well, but only in positive direction.

I have not got if there's stirrer own fluctuation at low speed and if there's stirrer own fluctuation at high speed.

 

MikeGoeman

"Only positive direction"

 What does it mean? Cannot imagine mixer fluctuation "only in positive direction, negative, all directions",

Also, mixer own fluctuation, what's really fluctuates in mixer? What do you mean by that?

Msorich

You can clearly see the motor and the shaft of the mixer ramping up and down at higher setpoint speeds,  but only in clockwise (positive) direction. The given setpoint remains constant. 

Now that i'm thinking of it, this could be the delay of the ramp generator 

I wonder why did you select u/f control method for mixer application.

It's definetely not best solution to keep constant speed under varying load. As mixer itself implies  varying load. Don't it?

Msorich

... maybe your module is too small.

What is set in p290?

Msorich

I wonder why did you select u/f control method for mixer application.

It's definetely not best solution to keep constant speed under varying load. As mixer itself implies  varying load. Don't it?

Msorich

 I didn't do the commissioning of the drive (back in 2007)

But speed (or torque) control would indeed be the better option.

As far as I've got you. In the past everything was working fine (stable speed within whole speed range). And now something wrong happened at high speed range. Does it happen at idle mode or under load?

Msorich

Problem solved!.

I upgraded the firmware of the flash card to v2.6 and it works again.

Why it's malfunctioning in the older firmware, no idea.

Probably older FW has reached its expiration date.

Msorich

Msorich

Probably older FW has reached its expiration date.

Msorich

 You can tell if it starts to smell bad

In all seriousness, with digital systems, there are only 3 reasons why you would have changes over time.

1.  Someone changed something.

2. Something external changed

3. Something broke.

I suspect someone changed a tuning parameter or a motor parameter.