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eltech
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Join Date: Mar 2011
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Vacon Drive

04/18/2011 6:41 PM

We are using a Vacon drive on a Gantry Crane, for the travel we are using two speeds 15Hz and 75Hz.When the power is removed from the motor a holding brake is activated which locks the motor.The issue is when it changes speed the loss of power in the transition seems to bring the brakes on.The brake gap is set good ,wondering if there is a setting on the drive that can fix the issue
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JRaef
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#1

Re: Vacon Drive

04/18/2011 8:10 PM

Several issues I don't quite understand:

  1. Why is it losing power when you change speeds with a VFD?
  2. Are you powering the brake from the motor power that is coming from the VFD? Or are you powering the brake from a separate power source through a Brake Control Relay controlled by the VFD?
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eltech
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#2
In reply to #1

Re: Vacon Drive

04/18/2011 8:52 PM

2.The motors are conical demag type.There is no direct electrical connection to the brake, it releases when there is power to the windings.(Electromagnetic brake).

I dont know why it is losing power, electricaly everything seems fine, ie the relays for speed, the brake resistors
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rhkramer
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#3
In reply to #2

Re: Vacon Drive

04/18/2011 10:11 PM

I didn't know what a conical motor was, so I did some googling:

from Brake Motors - Demag North America:

"The Demag KB conical-rotor brake motor provides you with a brake motor that utilizes a unique operating principle: The brake is not separately controlled, but firmly connected to the rotor, i.e. integrated. This means that motor start-up and brake release as well as motor switch-off and brake application are each synchronized."

So, is this a new installation? What has changed recently?

Based on the context, I'm guessing a Vacon drive is a VFD drive?

What is switching the power off during the transition between 15 Hz. and 75 Hz.?

It sounds like the brake will be applied when power is lost during such a transition, so maybe that transition has to be speeded up somehow?
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JRaef
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#4

Re: Vacon Drive

04/19/2011 12:00 AM

Which Vacon drive do you have?

If it's a vector drive, did you tune the drive to the motor? These conical brake motors are extremely flux dependent because the rotor moves along the shaft. If the VFD vector control algorithm hiccups for even a fraction of a second, the result is brake engagement. If you just used the default settings, the motor model that the vector algorithm is basing everything on may not be appropriate for a specialized motor like this. If the VFD has an "auto-tune" feature, I strongly suggest using it. If you did then maybe that isn't even good enough and you may have to enter the values manually, assuming you can get them from Demag.

I have heard of many problems applying VFDs to Demag conical brake motors. Not all VFDs are created equal you know. Vacon makes some good drives, they also make some cheap drives. Those two features never go hand-in-hand.

For those who don't know what a conical brake motor is, even after reading that (relatively useless) marketing piece from Demag, here's a cutaway that does more to explain it.

  • A. Brake Rotor Spring
  • B. Sliding Conical Rotor
  • C. Integral Brake
  • D. Single or two-speed
  • E. Aluminum die cast or cast iron housing depending on frame size
  • F. Integral Fan

When energized, the magnetic flux, which normally would just serve to establish a magneic field in the rotor, also causes the cone shaped rotor to shift horizontally (to the right in the above picture), which disengages the brake (far right). Any loss of flux strength, as in a vector algorithm that takes a brief nap, and the rotor spring pulls it back toward the left.

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34point5
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#5
In reply to #4

Re: Vacon Drive

04/19/2011 4:53 PM

I assume you just copy pasted that stuff under the pic and didn't proof read it

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eltech
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#6
In reply to #4

Re: Vacon Drive

04/19/2011 9:24 PM

Thank You for the info.It is a Vector Drive ( Vacon Nx).I did find out the drive had been replaced recently but not been auto-tuned.I will give that a try and see how it goes... After Easter.
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Elroy
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#7

Re: Vacon Drive

04/20/2011 8:17 AM

I'm not familiar with Vacon drives but you might want to check for a parameter such as flying start, and enable it. This allows the drive to transition to a new speed without the drive having to stop. It may correct your problem.

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JRaef
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#8
In reply to #7

Re: Vacon Drive

04/20/2011 2:01 PM

Elroy,

Vacon drives = TB Woods in North America, they also made the Cutler Hammer SV9000 drives, which is the same as the Nx Series Vacon.

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brandoncosta
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#10
In reply to #8

Re: Vacon Drive

11/11/2013 7:33 PM

If you take a look at the X-series drives from Vacon, they are still the same TB Woods drives, just a different name.
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eltech
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#9

Re: Vacon Drive

08/29/2011 1:41 AM

Thanks everyone for your help, I believe we have sorted the problem.We had the nominal voltage set at 240V and voltage at field weaking @ 100% of 240V, meaning that from 50hz to 87Hz the voltage stayed @ 240Volts.My knowledge from CR4 led me to believe that I can have 415Volts @ 87Hz which made perfect sense cause we still maintained the magnetising current the motor was intended for(V/Hz).I was advised against this by the vacon Guru(winding burn) and instead set the field weakining at 130% which gives me 312Volts at 87Hz.It is still better than initial set up.
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34point5 (1); brandoncosta (1); Elroy (1); eltech (3); JRaef (3); rhkramer (1)

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