[TowerTalk] rotating tower or stack : rpm

[Richard Riley]

Hi Al,

and thanks Charles, John and John (2!) for your swift input!  I had queried Green Heron initially but went on to purchase (the locally available) 4O3A RG...only to learn (after their online doc was subsequently updated) that their box only supports start/stop on lower voltage applications :-(.  So now I have the versatile 4O3A box, with all its bells and whistles (from a networking perspective)..but am missing the control signals to push in to a soft starter anyway.  Hence my switch of focus to a VFD solution, to simply slow things down if necessary.

All that said I am more concerned about soft stop than soft start.
I read a horror story about a tower that twisted itself around its guys in the Czech Rep. a year or so back. The rotor stopped, but the inertia (from the long boomed beams) just kept the tower turning.

All will be revealed shortly when the tower goes up, the motor is fully loaded and trials started.

Stay tuned :-).

rgds Richard 



-----Original Message-----
From: Al Kozakiewicz [mailto:akozak at hourglass.com] 
Sent: Wednesday, October 4, 2017 7:16 PM
To: Richard Riley <Richard.Riley at tango.hr>; 'towertalk at contesting.com' <towertalk at contesting.com>
Subject: Re: rotating tower or stack : rpm

It wasn't clear why you were concerned.

Soft starts are common in industrial applications, though I can't recall ever seeing one used where the output of the reduction drive was 1 RPM!

That motor spec sheet shows an integral  mechanical softstart (i.e., a flywheel) as an option.  Otherwise the standard industrial devices are candidates. Honestly, soft starts on big motors are more used to limit inrush current than for any mechanical protection. They can be as expensive as a VFD or as simple as an inductor.

Al
AB2ZY


________________________________________
From: TowerTalk <towertalk-bounces at contesting.com> on behalf of Richard Riley <Richard.Riley at tango.hr>
Sent: Wednesday, October 4, 2017 12:54 PM
To: 'towertalk at contesting.com'
Subject: [TowerTalk] rotating tower or stack : rpm

Hi guys,

my previous post (reference soft-start and frequency regulation of motor on a rotating tower) drew no responses :( :(...
...so I'll try it from another angle.  I'm about to erect 102ft of 20inch- to- a-side, triangular rotating tower (loaded with 12-15m boomed monobanders from 40-10) on a 3 phase motor, with a projected speed of 1rpm..and am concerned about the potential for start/stop stress.

You have a large stack or a rotating tower.

How fast does it rotate?

Have you employed a soft-start-stop system to prevent mechanical shock?

If so, what did you choose?

Your input appreciated!

73 9a1tt

Richard Riley

mob: +385(0)993 994 995
direct: +385(0)1 5494 303


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