vsd problems

Hello
we have had two burn outs of two 1.5kw vsd units on two different applications at the same time. the first vsd is situated 30 meters away from the borehole
the motor is a .75kw the vsd was fitted into a weather proof enclosure the ambient temp since installed has been sitting at 36-38 degrees c.
the second application is another borehole but situated 200meters away with the same conditions. ALL my readouts show that if infact its is reflective waves were present the motors would have burnt not the drives any suggestions

Try a line reactor.

http://ecmweb.com/design/line-reactors-and-vfds

thank you
i know fitting a line reactor should solve it. however im not convinced it was the cause of the problem exceasive ambient heat and would it take nearly three months to burn the vsds out`

karryinvestments said:

thank you
i know fitting a line reactor should solve it. however im not convinced it was the cause of the problem exceasive ambient heat and would it take nearly three months to burn the vsds out`

Click to expand...

Heat x time = failure. The accepted rule is that for every 10C over the operating temperature rating of a VFD, you cut the life of the VFD in half. Most drives are rated 40C operating temperature when enclosed. If your outside ambient is already 38C, the internal temperature in the box was likely well over 60C. Your drive would lose 75% of its design life, so if your drive would have lasted 12 years, failure in 3 years because of poor thermal design is not unexpected.

Mr Jraef
Thank you for this info it puts my thoughts at ease. in your experience is it a given that with reflective wave that the motor is the first to pack up, and secondly with the drive being twice the size of the motor should it not the motor burn out rather than the drive based on the theory that the reflective wave caused burn out of drive

Mr Jraef
Thank you for this info it puts my thoughts at ease. in your experience is it a given that with reflective wave that the motor is the first to pack up, and secondly with the drive being twice the size of the motor should it not the motor burn out rather than the drive based on the theory that the reflective wave caused burn out of drive

Do you have fan forced ventilation and or air con in your panel?

Are your VSDs rated at 40°C or higher?

Does your spacing around the drive match the spacing requirements of the drive installation manual?

For them to go at the same time though, there was something to trigger their failure. What do you mean by burnout? did it catch fire? did it give a fault?

Suggest it could have been a power spike on the incoming power supply, which was the final straw of an already stressed VSD from the excess heat.

Hi Australian
No no forced ventilation, both units are supplied from the same sources ,solar panel input during the day and genset for six hours at nite. I havent seen the units yet but have been told they damaged. the specs indicate that the units didnt need to be in a box we found them in a box supplied by their manufacturers distributor. the units filled 3/4 of the weather proof box. i get what you saying about them going at the same time.

vsd rated at 40 degrees

For two to fail at the same time sounds more like a mains voltage supply problem.

Supply is genset 380volts or solar

karryinvestments said:

Mr Jraef
Thank you for this info it puts my thoughts at ease. in your experience is it a given that with reflective wave that the motor is the first to pack up, and secondly with the drive being twice the size of the motor should it not the motor burn out rather than the drive based on the theory that the reflective wave caused burn out of drive

Click to expand...

Yes, that's been my experience. The motor winding insulation is typically the first thing to go in that scenario.

Refelected wave issues rarely affect the drive itself, they only affect the motor winding insulation. As the waves reflect back and forth between impedance changes (the motor terminals and drive terminals), the voltage potential builds up until it exceeds ratings. At the VFD end there is surge suppression to deal with it. But at the motor end there is not (unless you add it), so the portion continues on to the winding insulation eventually causes corona discharge inside of the motor, typically at the first turn of the windings.

As a gross general rule, over sizing the VFD increases the ambient rating based on the theory that the power devices are only operating at reduced capacity, with heat sinks designed for the higher value. There is a limit to that however and as you approach the actual ambient rating, that benefit drops off rapidly. So for instance you may have gone from 40C to 50C, but you will not get from 40C to 60C.