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@hourglass.com]
Sent: Wednesday, October 4, 2017 7:16 PM
To: Richard Riley <Richard.Riley@tango.hr>; 'towertalk@contesting.com'
<towertalk@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@contesting.com> on behalf of Richard Riley
<Richard.Riley@tango.hr>
Sent: Wednesday, October 4, 2017 12:54 PM
To: 'towertalk@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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