Solenoid question

Sudsmcduff

I have a industrial 875 36 volt. Replacing welded solenoid. Wondering what diode I need as the old one broke. The one for the two big studs. Or is that a pre charge resistor? Thanks

BGW

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scottyb

The pre charge resistor goes on the big studs. Use 10w 250-275 ohms Ω for 36v.
The suppression diode goes on the small terminals. Use 1000v 1-3 amp for 36v.

yurtle

I'll give ya one of each. Just pay shipping. Here:

Ya gotta post one more time, then at 25 minutes after the hour, you can PM me and give me your name and address. It's not really worth it for you to PayPal, so, consider it free.

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Sudsmcduff

Thanks man

yurtle

Package sent.

jpoarch

What are these for? My precharge resistor broke and my suppression diode looks to be cut.

JohnnieB

Precharge resistor: Reduces the amount of arcing and pitting of the solenoids contacts. The controller contains several filter capacitors and if discharged, they will try to draw hundreds of amps the instant the solenoid contacts close. Problem is that solenoid contact don't close and stay closed instantly, they bounce a few times first, so you get arcing.

For safety reasons, the filter capacitors have have a bleeder network that will completely discharge them withing a few minutes of battery being disconnected (solenoid contacts opened). The precharge resistor bridges the solenoid contacts and keeps the filter capacitors charged almost to the battery pack voltage, so the inrush of amps through the closing solenoid contacts is minimized.

Suppression diode: The solenoid coil is a strong electromagnet. When the circuit that energizes it is broken, the magnetic filed collapses and by doing so a strong pulse of electric energy in the opposite polarity is generated and causes arcing at whichever set of switch contacts opened to de-energize the solenoid's coil. The diode routes the spike back into the coil rather than into the solenoid activation circuit.

The pedal switch is the switch that usually breaks the circuit, and its contacts are rather puny, so the diode extends the pedal switches useful lifespan.

yurtle

Not thousands? Seriously...

JohnnieB

Theoretically, a completely discharged capacitor will try to draw an infinite number of amps, but the actual amp draw will be limited the resistance of the amp delivery circuit and the amp source's ability to produce amps.

I'm not sure if the instantaneous peak amp output of a deep-cycle lead-acid battery pack is in the thousands, so I went with hundreds.

Mblaze001

So what size resistor and diode would I need for a 48 volt setup?

Still trying to figure everything out for a rebuild.