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Re: [TowerTalk] DC vs. AC rated switch

Subject: Re: [TowerTalk] DC vs. AC rated switch
From: K8RI <>
Date: Wed, 28 Dec 2011 17:17:26 -0500
List-post: <">>
On 12/28/2011 1:25 PM, Ray Benny wrote:
> Tnx to all who replied. I'm going to purchase a larger switch from
> that should handle the current.
> Ray,
> N6VR
> On Wed, Dec 28, 2011 at 11:17 AM, AI4WM Bill<>  wrote:
>>    Depends on the internal construction of the contacts.  Switching and
>> inductive load may flash them when switched off.  Then locked rotor current
>> may be upwards of 45 amps for a few milliseconds until the armature starts
>> to rotate.  Locked rotor all depends on the starting load and the
>> efficiency of the motor.
Generally when you get to that size they recommend using a contactor.  I 
have a 5 HP motor used in a rotary phase converter. It says specifically 
not to use switches or circuit breakers, but use a contactor with 
overloads to provide power to the motor.
Fortunately I was given, (traded) for a NEMA size 2 contactor with 30A 
overloads. The contactors alone run between $500 and $600 retail.
Parts?  Head for e-bay! Lots of contactors and parts for a fraction of 


Roger (K8RI)


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