[SBE] Phasor current draw

[Cris Alexander]

Okay. I thought you might have drawn a diagram.

Sounds like you're on the right track. I think you'll be fine allowing for
8A per solenoid (Kintronics says it's 7A, but that's for a new solenoid).
 
______________________________
Cris Alexander, CPBE, AMD, DRB
Crawford Broadcasting Company
Denver, Colorado
(303) 433-0104
(303) 433-0905 Fax
Assoc. Member AFCCE

  _____  

From: sbe-bounces at sbe.org [mailto:sbe-bounces at sbe.org] On Behalf Of Edwin
Bukont
Sent: Tuesday, July 14, 2009 7:01 AM
To: sbe
Subject: Re: [SBE] Phasor current draw


There is no diagram. The existing control to choose DA or NDA is an
interesting rotary switch, that operates somewhat more like the old leaf
switches.  There are 8 poles.  Four per side of the rocker cam that the
switch handle operates.  In each set of four there are two NO and two NC
switches. The arrangment of common contacts makes this effectively a 4P/DT
rotary.
 
To remote this means first having a 4P/DT toggle to choose between the
commons of the rotary or the commons of the new latching relay.  
 
The system control circuitry would get paralleled to the new relay.  The
relay has to latch to emulate a rotary switch with two fixed positions.  
 
I have all that figured out.  The issue was how much 240VAC current to allow
for through the relay contact.  I already said the new relay would be a
24VDC coil.  The consensus seems to be to allow 8A per contactor coil.  
 
So that means it will take 30A relays and is probably why it was never done
in the past.  I suspect I will need to use actual contactors rather than
relays for this application.
 

Edwin Bukont CSRE, DRB, CBNT 
V- 240.417.2475; F- 240.368.1265 

 




 

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From: crisa at crawfordbroadcasting.com
To: sbe at sbe.org
Date: Tue, 14 Jul 2009 06:50:20 -0600
Subject: Re: [SBE] Phasor current draw


I can't imagine why you would need a latching switch. The reality is that
would necessarily rely on the end-of-travel NC microswitch on the RF
contactor itself to open the circuit to the solenoid when end-of-travel is
reached. How many times over the years have I seen solenoids burned out
because those microswitch contacts did not open?
 
Love to see a diagram of that thing...
 
______________________________
Cris Alexander, CPBE, AMD, DRB
Crawford Broadcasting Company
Denver, Colorado
(303) 433-0104
(303) 433-0905 Fax
Assoc. Member AFCCE

  _____  

From: sbe-bounces at sbe.org [mailto:sbe-bounces at sbe.org] On Behalf Of Edwin
Bukont
Sent: Monday, July 13, 2009 3:18 PM
To: sbe
Subject: Re: [SBE] Phasor current draw


Cris
 
the bizzareness is that the Tx and DA modes are controlled by momentary
closures,,,but the DA/NDA is a rotary 4P latching switch.  Thus I figure I
need a latching relay that can handle the total current rather than a simple
actuator paralleled.
 
The fun of old plants and no plans.

Edwin Bukont CSRE, DRB, CBNT 
V- 240.417.2475; F- 240.368.1265 

 




 

  _____  

From: crisa at crawfordbroadcasting.com
To: sbe at sbe.org
Date: Mon, 13 Jul 2009 14:29:39 -0600
Subject: Re: [SBE] Phasor current draw


Edwin:
 
If those are the solenoid-type RF contactors, at 250 volts you can expect
about 6-7A current draw per switch nominal, but the inrush current may be
considerably more. So with five towers, it seems that a 30A relay would be
boderline. 
 
You should be able to jeep some 24V relays in there to control the phasor
remotely. Just hang the NO contacts of a 24V-coil relay across the actuator
lines for each mode.
 
______________________________
Cris Alexander, CPBE, AMD, DRB
Crawford Broadcasting Company
Denver, Colorado
(303) 433-0104
(303) 433-0905 Fax
Assoc. Member AFCCE

  _____  

From: sbe-bounces at sbe.org [mailto:sbe-bounces at sbe.org] On Behalf Of Edwin
Bukont
Sent: Monday, July 13, 2009 2:06 PM
To: sbe
Subject: [SBE] Phasor current draw


I am trying to create a DA/NDA remote control for a 3-tower phasor system.
The system has remote for choosing transmitters and Day or Nite. It does not
have remote for choosing DA/NDA.
 
Currently, someone has brought out the Tx and D/N to 240VAC relays with 30A
contacts.  Is this really necessary?
 
The mode change itself appears to throw maybe 5 contactors including the
towers.  I realize that in the DA mode it has to support the current
involved with switching of Day and Night.
 
I want to do my additional control with a 24VDC coil and contacts rated at
15A/250VAC.
 
Am I missing something here.  Do I really need those big power relays or
will something smaller suffice.  I do not know what the current draw is,,and
it would be difficult to amp clamp.
 
Anybody have any ideas what a 30-40 year old three tower, 3 modes Phasor
array might draw in Amps at 250VAC during switching?
 
Thanks

Edwin Bukont CSRE, DRB, CBNT 
V- 240.417.2475; F- 240.368.1265 

 



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