Batboard

Group,

With DC - DC power converters that offer the Overvoltage Protection feature...

What exactly does this overvoltage feature protect against? Is it the voltage on the converters INPUT side or on the OUTPUT side or both sides?

Does anyone know? I would like to learn more about this feature.

Thanks

Doug

In the Astron DC/DC converters that I have repaired(N2412-20) the overvoltage protection is on only the output(12V in my case) side of the converter. It's not very fancy, just an output biased zener diode driving the gate of an SCR tied between the output + and -. If the PWM regulator fails, the output goes above 14.8 or so and the SCR conducts, shorting the output. The PWM regulator chip senses overcurrent and shuts down until the power input is cycled.

Do you know if any of these converters from any manufactuer offer voltage spike protection on the input side of the converter?

I am wondering if any of them make it so that it will protect the converter itself from being destroyed from very high voltages for very short periods of time.

Doug

What's the application? Sounds like you need some more engineering if the input side occasionally has "very high voltage" spikes.

tvsjr wrote:What's the application? Sounds like you need some more engineering if the input side occasionally has "very high voltage" spikes.

Agreed, usually DC-DCs end up knocking down 24 to 12 in commercial and industrial vehicles and I haven't had a lot of problems with alternator spikes. Other case may be a -48 VDC rectifier/battery UPS system. You might need to knock that down to 24 or 12. Even then, your rectifiers should have output protection preventing anything over 54 VDC.

Guys,

The application is in a 64/75 Volt DC system, when the equipments engine is not running the voltage is at 64 Volts DC, but as you start the engine the voltage will jump up to 429 Volts for about .5 to 1.0 seconds and then immediately drop back down to 64 Volts DC again and as the charging circuit charges the batteries the voltage slowly rises to about 75 volts DC, the actual voltage spike that jumps up to several hundred volts is a well known problem in this electrical system and no one has indicated a fix for this issue other than to obtain specific DC - DC voltage converters that are equipped with this so called "Voltage Spike Protection feature" or remove power to the converter before and while starting the engine then turn the power on after the engine is started.

Im not looking to get into the technical issues or debates about the engineering or design of the electrical system, I would just like to know more about this "Voltage Spike Protection" feature that is built into the converters on the terms of what it actually does or doesnt do and what or how it protects and any other information that can be provided about this feature.

Anyone experienced with these devices that could shed some more light on their internal workings?

Thanks much

Doug

I *highly* doubt you're going to find a device that states it works at 64/75 volts but will routinely tolerate a 429 volt spike.

Do the batteries get subjected to the 429V spike? I'd go look at the voltage across the batts during crank. I highly doubt they get subjected to that large of a voltage spike, otherwise you'd be replacing failed batteries right and left. Based on your professional affiliations and location, I'm going to assume this is a system in a locomotive, nominally 72V. I'd look at the battery voltage and pick up 12V by going across a single cell there, assuming they don't get spiked. Otherwise, I'd tie a relay and/or timer into the start button so that your DC-DC convertor would get isolated when the button was depressed and remain so until the starting cycle completed.

Probably not, but that is why I am asking about this High Voltage Protection Feature. I want to learn more about it so I know what its capable of protecting and what exactly it is protecting.

I would have to assume that the batteries are seeing this spike since the 'tap' is directly off the battery switch which is connected directly to the batteries. Please keep in mind though that this 429 volt spike occurs only for about a 1/2 a second, 1 second at the very most, it occurs so quickly that my digital volt meter barely picks up a reading of the spike on my meter, but the spike is indeed there. I like the idea of the relay and timer, but I have been looking for 75 volt relays and have not found anything available, yet, and timers in this type of situation I am not familiar with.

We are getting off subject, may we go back to discussing the Voltage Spike Protection Feature?

I would like to know what this feature actually protects. Anyone know anything about this feature?

Thanks much

Doug

P.S. TVSJR if you want to discuss the other 'issues' more in detail please PM me.

Servicemate switch mode regulated voltage converters are heavy duty DC to DC converters with an extended input range. Features include: Weather-proof, vibration resistant, high efficiency, short circuit protected, thermal protected, soft start, reverse voltage protection and input/ output filtering. Designed especially for use on 24v, 36v, 48v construction equipment, lift trucks that use standard 12 volt lights and two-way radios. Note: Only SM2412-15 & SM2412-25 models are designed for use on equipment with regenerative braking. Warranty is voided if SM2412-2.5, SM2412-5; or SM2412-10 is installed on equipment with regenerative braking.

They are made by Translectric

This is the description from Tessco.

The unit listed allows for regenerative braking, aka reversing voltage to slow or stop a device, I see they protect from about all sides of the spectrum but do not show a current voltage above 48 VDC. This would be a direction to look in, give them a call and they can probably configure a unit to meet your needs depending on the load.

I have used these with good success on Cat heavy equipment with the double throw starter solenoids which politely reverse voltage until the key is released.

CoM