RE: Economizer circuit

[Tech Man <TechMan@hcitech.com>]

A much simpler and less costly approach is to use a capacitor in series with
the resistor and works as follows:  Before the capacitor is charged up, 
it appears as a dead short and allows full current to reach the coil of the
contactor providing fast turn-on times. As soon as the
capacitor charges, it appears "open" so current can only flow through the
resistor dropping the current through the coil.  When power
to the coil is turned off, the capacitor discharges through the "bleeder"
resistor and is ready for the next cycle.  It is best to 
determine the value of the capacitor experimentally since coil resistances
vary, but generally a good place to start is around 1500 mFd.
Also, make sure that the working voltage of the capacitor is appropriate for
the coil voltages involved. 

> -----Original Message-----
> From:	Bryan in San Jose Ca [SMTP:everuplate@eisa.com]
> Sent:	Thursday, March 30, 2000 6:39 PM
> To:	ev@listproc.sjsu.edu
> Subject:	Re: Economizer circuit
> 
> Hi,
> Not a snubber, it's a circuit to reduce the power consumption in the coil
> while the relay is "on". A simple approach is a 2 stage circuit in which
> the
> first switch would "start" the relay by providing full coil voltage to
> engage the relay, then a 2nd switch would be turned on in parallel with a
> series resistor to "hold" the relay closed and lower the power dissipated
> in
> the coil when the first circuit is switched off. The overall power
> dissipated in the coil would instead be dissipated in the series resistor
> "hold" circuit.
> For this to work, you would have to find the minimum holding current, add
> some margin, then calculate a series resistor value for the hold circuit.
> Need more help? drop a line....
> 
> For their built in version, they use a PWM circuit instead of the simple
> external resistor approach.
> 
> Hope this helps...
> 
> 
> ----- Original Message -----
> From: Michael Bearden <techsan@pacbell.net>
> To: <ev@listproc.sjsu.edu>
> Sent: Thursday, March 30, 2000 7:48 PM
> Subject: Economizer circuit
> 
> 
> > OK, I bought a contactor(Kilovac)which says (on the case) 'Requires
> > economizer circuit"...Is this the "snubber" which I have seen discussed,
> > or a different animal altogether?
> > Michael B.
> >