Re: Economizer circuit

["Bryan in San Jose Ca" <everuplate@eisa.com>]

 ......I think you meant to say, the cap is in parallel with the
resistor.....When it is in series with the resistor, the cap fills up and
the current falls to 0. That would allow a single switch, parallel R/C
solution. Funny, but I reminded myself just now that I did it for a riding
mower relay for my EV motorcycle. Amazing when you get older, it takes
longer to remember things...

----- Original Message -----
From: Tech Man <TechMan@hcitech.com>
To: <ev@listproc.sjsu.edu>
Sent: Friday, March 31, 2000 6:25 AM
Subject: RE: Economizer circuit


> 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.
> > >
>