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Regenerative overvoltage trip during constant speed...

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sw_ross

Senior Member
Location
NoDak
Updates from today...

The fault happens only when the gazebo is being reversed, and it happens at a specific location on the track.
Also, it only happens when it is loaded up with the weight of the band and instruments.

In the spot where it happens there is a one-inch elevation change in the track (over about a 3-4 foot distance) which means at that spot the gazebo is going downhill... I'm guessing that is where the regen is occurring.

I asked about any change in weight since this situation didn't happen last year. They said nothing significant, maybe 100 lbs. I don't know how much the gazebo weighs but it's got to be at least 3000-4000 lbs.

I adjusted that parameter 22 twice, going up to 170 and then 185. That's didn't change anything. It faulted each time.

I need to continue reading through the manual and figure out if its possible to resolve the issue.
 
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paulengr

Senior Member
If you are in regen not only are you eating into the room the drive has to work with but it reduces how much you can regen because of reduced firing angles. Regen works much better in undervoltage conditions.
 
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sw_ross

Senior Member
Location
NoDak
myspark said:
@OP

While I take everything you’ve said is the actual event/events that’s happening or have happened—I would not arbitrarily change the setting at this point (although-- perhaps that’s what it will take to correct it.)

You’ve indicated that the unit is: “the motor stalling out during usage.”

What I’m not quite clear is: what did they do to resume the operation? Did it restart when they pushed the start button? And what did you find when you showed up?
Now, let’s take that “stalling during usage” bit.
This tells me that the unit is experiencing unstable drag while in motion—not during accel or decel.
I’m sure you’ve done those T-shooting-- along with some suggestions by contributors --as to what might be happening. (the purpose of this forum)

I understand that you noted the cause of the anomaly.--and yet still need to be addressed.

This Mitsubishi Series 700 Model has a lot of improvements to it from their early models.
Before the unit trips on overload /over voltage, it goes thru a stage in which “it” enters a threshold where it determines whether a glitch is occurring (harmonics can cause this anomaly)
If the anomaly is sustained--depending on the duration—the overload protection would trip to protect the drive (VFD) and the motor.

This unit is capable of storing valuable information for convenient T-shooting.

Peruse the manual from cover to cover and it will tell you the history of the events that caused them-- or when the problem occurred.
It can store up to eight (8) events.

Keep us posted what you come up with.

Note:
As I was poring thru the manual—I noticed that this model is designed for a 1.5 HP motor minimum.
Your application (you said) is 1 HP.
Click to expand...
When I described it as "stalling out" I meant that it faulted, giving the error code stated.
When the motor faults at the specific location stated the operator (who has come to anticipate it) only has to hit the reset button to continue using it.
 
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winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
The slight downhill ramp is a perfect example of a regeneration situation.

The gazebo is being pulled downhill, and the motor is being pushed fast enough to start acting as a generator and trying to restrain the load. Whenever you have a load going downhill you have stored potential energy that has to go somewhere.

My guess is that last year more of the energy went to friction (lubrication change? cleaner tracks? Building settling changing the slope?) and this year you are getting just enough regeneration as electricity stored in the capacitor bank.

You have several options at this point.

1) Add a braking resistor. This is a resistor that gets connected to the inverter to bleed off regenerated energy and convert it to heat.

2) Slow down the system. If you reduce the drive frequency and the speed of the gazebo travel, then you reduce the regeneration power. You still have the same _energy_ to dissipate, but more slowly. This might give the natural losses in the system time to dissipate the energy. You have losses in the motor, so if you can move slowly the regen might simply go to covering those losses.

3) Use the regeneration avoidance function of the drive. As another poster mentioned, this drive has a feature were it will stop trying to restrain the load if you get to a regen situation. If you enable this feature then the drive will let the gazebo accelerate down the ramp, letting the excess energy get converted into speed. Then friction will slow things down again and the motor will go back to working to move the load.

-Jon
 
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RumRunner

Senior Member
Location
SCV Ca, USA
Occupation
Retired EE
sw_ross said:
I don't know anything about brake resistors...
Where does it mount?, etc.
Click to expand...


I don't know anything about brake resistors...
Where does it mount?
.........

When I described it as "stalling out" I meant that it faulted. . . . . . .
.........


The performance of the unit (gazebo) in terms of how energy is utilized by converting to: rotating motion, inertia to a flywheel (if there is one) that would be a source of kinetic energy, duration of coast when a command to stop is given--would dictate the type of braking system.

This gazebo application doesn't really need high performance VFD and motor to move it . . it only moves at snail-pace. Soft starting and (maybe) speed regulation is what this VFD is for.

Given this criteria --dynamic braking. . . be it regenerative or using brake resistors. . .the necessity for the need of electronic brake system seems to be a low priority.

I would be concerned if this gazebo moves at 40 MPH.

I agree with one's post that the strength of the regenerative braking is proportional to the energy required to move an object.
Increased movement of an object generates a substantial amount of energy. When you give it a command to stop the object tends to keep moving.

It is this built-up energy that we put to use in the braking stage. Without the speed there is no available energy that is regenerated.

You can't get anything out of nothing.

Reduced firing angle in the half sine wave means low output--- which equals minimal energy to enable regenerative energy to be useful.
So, regenerative or resistor braking wouldn't even have much merit in this setup other than soft start.

To OP:
You wonder where the resistor would be located.
It would be located outside the control cabinet and exposed to ambient temp for heat dissipation.

The resistor look like a ceramic-dipped rolling pin with cooling ribs all around it and usually inside a wire cage.. . .it gets hot (temp)

So much for pedagoguery.
 
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