[TowerTalk] rotating tower or stack : rpm

[Jim Thomson]

Date: Wed, 4 Oct 2017 16:54:16 +0000
From: Richard Riley <Richard.Riley at tango.hr>
To: "'towertalk at contesting.com'" <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

##  1 rpm =  6 degs  per second...which is WAY too fast for a rotating tower imo.    You need some ramp up...and ramp down capability.  I assume your motor is 3 phase, and runs on 50 hz ?   Trying to speed up and slow down a 3 phase motor
will be  a trick.  Your VFD  may well be your best bet..albeit expensive.   How to implement a 3 phase VFD  drive  into your configuration  for automatic or manual control may not be as simple as it looks.  The 3 phase motor is  reversible, which just complicates things some more. 

##  These small prop pitch motors  typ turn at just  .55  rpm.    And even .55 rpm is too much to slow things down..gently.  The GH controller works good with the small Prop pitch..since it has ramp up /down included.   Then you are not slamming the torque on, all at once.  Hence the ramp up portion.    The ramp down of course, ensures everything does not come to a crashing halt.   A rotating tower has a lot more total weight vs a rotating mast.   You might want to runt his past 4O3A .

Jim   VE7RF