Siemens VFD Drive - Opening of Resistance

It's taking too much current. Which means that one or more of the following applies:

• The motor downstream of it is faulty.
• The cabling downstream of it is faulty.
• The winch speed is too fast for the load.
• The winding drum friction is too high.
• The load is too heavy for the winch.
• etc.

What is the fault code?

....and what does the Siemens specialist say on the subject?

To add to PWSlack's list:

• VFD is not programmed per motor nameplate values (common error)
• The "resistance" you speak of is Dynamic Braking Resistors, and they are over heating because they were not properly sized for the application and/or duty cycle.
• They WERE properly sized per the original tender specifications, but you are EXCEEDING the designed duty cycle.
• etc. etc.

In other words, you have not provided anywhere near enough information for anyone to help much. As was suggested, did you get someone from Siemens or the crane manufacturer to get involved? This is the type of thing that needs up close and personal investigation.

I suppose it is the braking resistor that is warming up. Normally this comes from kinetic energy transfer to electric energy in the DC capacitor inside the VFD.

If there are more than one VFD's, you could connect the DC bus of the VFD to each other. This only works when one motor (VFD) consumes energy and an other motor (VFD) at the same time delivers energy.

Other solution,

• increase the deceleration time,
• mouting a bigger braking resistor (one with a bigger thermal capacity), keep in mind that the ohm value is the same.
• better cooling of the braking resistor

I think that you are refering to the braking resistor, for your application I would increase the wattage of the resistor, and ensure that it is well vented, possibly some forced air cooling will help.

I also presume that the VF Drive is on the main travel, so I dont think that increasing the slow down time would be a good idea, from a safety point of view.

Please Visit the web site mentioned below. They are pioneer in India in designing resisters for above applicaions

The web site not included . please find it as www.nationalswitchgears.com