[Amps] Crydom Solid State Relays

[Bob Maser]

SInce my inventory consists of 40A SSR's, I am planning on using them.  Re: safety, I never touch anything inside the power supply until 3 things have occurred; I have watched the DC voltage drop to zero with the help of the bleeder resistor, I have disconnected the AC from the wall, I have shorted out all the secondary "hot spots" to ground with a shorting stick.  Since I also use a 40A circuit breaker at the AC input of the power supply, that prohibits 240AC from entering the power supply.

Bob  W6TR
  ----- Original Message ----- 
  From: TexasRF at aol.com 
  To: bmaser at tampabay.rr.com ; amps at contesting.com 
  Sent: Thursday, January 29, 2009 5:05 PM
  Subject: Re: [Amps] Crydom Solid State Relays


  A couple of comments from a user: The solid state relays do not completely shut off in the off condition; you will have some residual voltage on the output terminal when you might expect zero volts.

  The 40 ampere rating can be exceeded with a capacitor type filter circuit. It has been mentioned many time in the past that peak ac current can be 5 to 10 times average with capacitor filters. Solid state relays don't like this. You might want to consider 70 amp rated relays as they don't cost that much more than the 40 amp units.

  When one of the SSR's fail, it is invariably in a shorted mode. Needless to say, this is an extreme safety hazard. Never assume that a power supply is off; it may not be!

  73,
  Gerald K5GW



  In a message dated 1/28/2009 7:08:01 P.M. Central Standard Time, bmaser at tampabay.rr.com writes:
    The power supply of my new amplifier will be using 3 40A Crydom SSR relays, 
    One on each leg of the 240VAC and another in one leg to short out the step 
    start resistor.  I have been planning on using the SSR's w/o any resistors 
    or capacitors across the control connections but I have been advised that I 
    should put resistors and capacitors across the control connectors to prevent 
    RF from affecting the SSR function and possibly causing "chatter".   I would 
    appreciate some feedback from the group.  I don't believe that Jerry 
    Pittenger K8RA used anything in the 3CX1500D7 amp that was featured in the 
    2006 ARRL Handbook.

    Bob Maser  W6TR 

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