Re: Frequency for SSRs using PWM

[adt22-at-drexel.edu]

----- Original Message -----
From: Joe Sommer <anvilus9-at-adelphia.net>
Date: Tuesday, March 16, 2004 10:02 pm
Subject: Re: Frequency for SSRs using PWM

> 
> Ted,
> 
> At 07:54 PM 3/16/2004 -0500, "flier" <FLIER-at-sbcglobal.net> wrote:
> >What PWM frequency (or period) are you guys using
> >with the SSRs for your motor speed control?
> 
> I use 1 KHz.  You can actually hear the motors whine at
> 1 KHz when they stall.
> 

Joe,
Electromagnetic relays usually have a life span that is in the millions of switches. 
 Although I can't find it now, I thought I saw a site stating SSRs were also rated 
for a minimum number of operations - is that true?  

Also what is the range in frequency you have with the PICs?  

Hypothetically if the SSR was good for 1 billion ops
and you used a 1KHz frequency your SSRs would last ~275 hours which is pretty long.  
I'm sure many other things would fail before your 275 hour tune-up.  But I just 
wanted to bring it up because others might want to consider the price and life of 
the SSRs when you are choosing a frequency.

So that being said, anyone know how many ops an SSR will take before it dies?

Or how about the rating of high end ESCs do they have a known lifetime?

-Amir