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Help with Proportional SSR

Discussion in 'General Electronics Discussion' started by TurboTim, Mar 31, 2017.

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  1. TurboTim


    Mar 31, 2017
    I am working on a car project where I have had to add a second fuel pump to supplement added horsepower. The original fuel pump is controlled by a module that looks to vary the voltage to speed the pump up or slow it down. I dont want to pull too many amps with 2 fuel pumps wired in parallel to the original module so I am wondering if I can use the output voltage of the original module as an input to a SSR that will then copy the same voltage but will be able to handle 30 amps with ease. I have ran these pumps on a duty cycle also so I am okay if the output in a PWM signal.
  2. Bluejets


    Oct 5, 2014
    Now that's a good question. Should be ok as far as I can see. I imagine it depends on whether or not the SSR will respond to the PWM frequency.
  3. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    I wonder whether the original controller does output PWM, too? Using a
    It may work, but SSRs are not that fast...
    Take for example this SSR: TLP3450. Switching time is max. 200µs on, 200µs off, a total of 400µs or 2.5 kHz. Since power dissipation duricng switching is much higher than in the on or off state, the relay may overheat at 2.5 kHz.

    Since no isloation is required, a SSR is taking a sledgehammer to crack a nut. A simple power transistor may suffice. We need more information on the voltages, currents (and possibly wavefomrs) involved here.

    It will by no means work if the controlling voltage is a linear voltage. The an amplifier would be required. However, I doubt the controlling voltage to the pump is really a linear voltage. PWM is so much more efficient and therefore so much more likely to be used.
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