Problems with Danfoss Drives

The generator set supplier and the drive manufacturer should be at the top of the list.

Hi.. I can help you zero-down on the root-cause of the problem. Can I have the single-line diagram of the power-flow in your facility right from Utility point to Drive.

Regards

Sanjeev

Hi.. I am not able to give you a single line diagram, but will try to give you a picture.

we are a packaging line for Coca- cola, with mains and gensets, but never in paralell, then we have 1600A breakers and a switchgear, from here goes to a main DB that supplies everything (motors, pumps, valves. drives(380 side),etc..) and to a UPS and AVR for PLC and small signal instrumentation. As you can imagine we have a lot of inductive currents, plus the drives are profibus.

Thanks for your help

Try these :

http://www.alibaba.com/product-tp/101590704/CVM_k_2_Three_Phase_Power.html

This equipment will help you match the PHASE before switching to and from genset. But I do not know if gensets can actually match the Phase of the huge generators use at dams of power plants.

Hi Carlos,

I assume the failures occur when the power is cut from the supply company. If so then your problem could well be the inductive spike caused when the power fails. Also motors with high enertia loads turn into generators which can cause high voltages. If you can find out which pieces of your plant equipment are causing this then you need to add suppression to these.

If you cannot find the culprits then you can add protection to your VSDs. Use a fast blow fuse in the feed to each VSD and a varistor across the input. The varistor will clamp the voltage and blow the fuse before the voltage reaches destructive levels in the VSD. Carry a stock of these as they usually fail when protecting the circuit.

You may find that you already have this protection inside your VSDs and that with a bit of research you can get the appropriate components and have the VSDs repaired locally by a competent electronics tech.

Hello Carlos57

There are two major mechanisms for input failure.

1. Voltage transients.
2. current surges.

It is possible that when the supply is switched over from generator to main supply, that there are voltage surges due to rotating motors and the like. These voltage surges will cause a current surge through the input rectifiers as the voltage is applied via the rectifiers to the DC Bus capacitors. The current surge can easily cause rectifier failure.

After the genset is taken off line, there can be a drop in the DC bus voltage followed by a sudden re-application of full line voltage. Once again, this can cause a current surge as the mains voltage charges the capacitors back up to the normal rail voltage.

The addition of 3% or 5% line reactors and semiconductor fuses in series with the input to each VFD will help to a) reduce the amplitude of the current surge and b) provide rectifier protection if the current gets too high.

Best regards,

Mark.

we suggest you to use 3 Phase AC Line chokes. This introduce additional impedace & protect drives from power problems

contact info@sve.co.in for full details

regards

Srinivas

Virgo Technologies,

India

Emeson AC drives Dealer