VFD failure

  • Thread starter Nelson DeFreitas
  • Start date
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Thread Starter

Nelson DeFreitas

Hi

I Hope someone out their can help me I have the following problem:
I have a 10 HP VFD Reliance SP500 Series 600V 3 Phase, 1740 RPM
I have line reactor connected on the line side (recommended by MFG)
Supply voltage is 570-585 VAC
Connected to a 10 HP motor/gearbox/pump

The problem is every 12 hours or so the VFD trips out on HU (high bus fault). I would like to know what causes this and how can I prevent it?

Thank you very much.
 
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Paul Hrynyshyn

This generally happens the motor is decelerating, the motor generates voltage back into the drive. The easiest solution is to first increase the deceleration time untill the problem goes away. If increasing the deceleration time cures the problem, but you need faster deceleration you will need to use a dynamic braking kit, to dissipate the regenerated power through a resistor.

If increasing the decel time doesn't solve the problem, turn your carrier frequency down as low as possible, ensure your wiring between the motor and drive is good, check the manual to make sure you haven't broken too many wiring rules, check you haven't run the motor wiring more then 250ft.

If you have run the wiring to far or broke a lot of the wiring rules an output reactor can help. You can use a normal line reactor, but it will increase the minimum deceleration time (it make the power regeneration problem worse, a dynamic braking kit will help), or you can use an open core output reactor, more expensive, but it won't cause the regen high bus voltage problems.

If the problem only happens during stopping, you could try going to coast stop mode, if it still happens in coast stop mode, you can add an output contactor to the drive to seperate the drive from the motor during stopping.

Hope this helps.
Paul
 
What is the application is it a high enertia load that is being stopped to quickly, or is it a section of a web processing machine that operators set draw between sections and allow this drive to be overhauled. You may just need to add dynamic braking for stopping power. Let us know.

Mike
 
If this happens twice every day at around the same time (every 12 hours) then you may have an electrical supply problem. One of our buildings has a heavy electrical heating load that when shut down would cause the electrical supply to raise just enough to fault some of the VFD's.
Transformers were installed to reduce supply voltage to the lower range of the drive when heating equipment is loading it.
 
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Kevin Cooper

Bus Overvoltage has been attributed to capacitor switching, either in the plant or by the utility.
If this happens regardless of whether the motor is running or not, this may be the cause.

Regards
Kevin Cooper
 
W

William Hinton Sr. Electrical Engineer @

High voltage spikes from any source can and do cause an overvoltage fault on VFDs. You did not indicate the power source as being a WYE or DELTA but if it is an ungrounded power system we have only found one solution that always works.

There have been various ways to help this condition but the only positive solution that suppresses all the spikes on all equipment fed from a power transformer. That is one unit per plant not one per drive. The solution to this problem has been the installation of a Phaseback EMTVSS from http://www.applied-energy.us
 
S
Hi Nelson,

The VFD converts the AC input power into DC, which is then inverted back to AC for consumption by the motor. AFAIK, the only way you can get a overvoltage on the DC bus is to put in too much energy, either by way of poor regulation on the rectification stage, or by means of energy coming back from the motor. If the motor is used to drive an overhauling load which must be decelerated this is called regeneration, and sends power back to the drive. In practice, this is the most common cause of high bus voltage.

The drive has the capacity to dissipate a small amount of regenerated power, like in the range of 10-20% of rated drive hp. If your deceleration power requirements are higher than this, you will need a external resistor, called a braking resistor, connected to the DC bus to sink the power.
 
D

D. Smith - Manufacturing Plant Owner

Another solution that works extremely well is the Redi/Volt Energy Management System from Volt Tech, Inc. Funny thing is that when the system gets applied not only does it take care of all transients, it completely protects the entire system from any electricak voltage spikes, sages, or surges, and each unit comes with a $100K connected equipment warranty - which definately covers any damage to any VFD's or any other electrical equipment. I have this system installed in my facility and am 100% satisfied with its performance and it has knocked off an average to date of 32% from my energy consumption. I would recommend this system to everybody. The guys name at Volt Tech is Damian and the website address is www.volttech.com if anybody is interested.
 
Hi Nelson:
Have you tried setting up an S Curve
Accel / Decel time will help, the S curve will enhance the DC bus filter. advance your decel time then enable your S Curve and drop a time value into in.
Please post what you have done and found so far
Good Luck
 
W

William Hinton

There are only a few reasons for an OVER VOLTAGE trip in a VFD.

The easiest thing to test is what the actual line and phase voltages are at the drive input wiring. The power transformer may need to be taped down a tap or two (2 ½% Increments) if the nominal voltage is close to the drives maximum voltage, typically +10% and some allow -10 or 15% for under voltage.

I do not expect a pump to run on (coast) when you are shutting it down and in many pump applications they allow the motor to spin down without dynamic breaking or deceleration.

When line reactors are installed at the line side of a drive there is added an additional voltage drop across the line reactors which limit the voltage to the drive which can reduce the motors starting and running torque. Even worse is the tendency to use deceleration control which makes the motor generate power which generates a voltage higher than the line voltage to overcome the voltage drop across the line reactor. A line reactor, like other inductors, resist a change in current but they do a poor job of voltage control.

The high voltage spike causing this fault is typically not discovered with a multi-meter as even a fast rising voltage spike can cause this fault. They generally fault at a voltage level irrespective of time so a multi-meter will not show it if it is caused by a transient voltage spike.

If these steps have not solved your problem by now, (14 years) there is a device which will stop all the voltage spikes and balance the phase voltages to protect the drive and allow clean noise-free operation. This is called a VSGR (Voltage Stabilizing Ground Reference) as shown and described in the IEEE 142 grounding standard. The marine industry uses them on every vessel covered under the ABS (American Bureau of Shipping) standard which is under the control/jurisdiction of the US Coast Guard.

The VSGR comes in various sizes based on transformer or motor size and you can read more information about this technology at: www.Phaseback.com

I hope this helps,

William Hinton
Director of Engineering
Applied Energy LLC.
 
Before you start needlessly throwing money at this, you need to determine if the OV fault is taking place while the drive is running, accelerating, decelerating or stopped. It's important to understand that in order to properly identify the right solution.
 
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