"Voltrap" Transient Voltage Suppressor
"Voltrap" Transient Voltage Suppressor
(OP)
My company Currently has been using a device called a "Voltrap". From what I understand it is a bi-directional Selenium Diode. We use them in hazardous duty control cabinets to prevent a trasient voltage spike or flashover due to the inductive kick of a relay coil. These are getting very hard to find and are quite expensive. I have been hoping to find a cheaper alternative. The system voltage is usually 125 Vdc. Anyone have a better understanding of these and could point me in the right direction.





RE: "Voltrap" Transient Voltage Suppressor
Today, most transient protection is performed by MOV's (Metal Oxide Varistors) - a bi-directional type device, -OR- silicon transient protection devices (i.e. transzorbs)- available in unit and bidirectional configurations. Other available devices, but somewhat less common in use because they clamp the line once triggered consist of gas-tube and thysistor-tybe ("surgectors") devices.
I suggest you down-load some application notes on MOV type devices. MOVs are available in a wide range of voltages and power ratings.
RE: "Voltrap" Transient Voltage Suppressor
RE: "Voltrap" Transient Voltage Suppressor
RE: "Voltrap" Transient Voltage Suppressor
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RE: "Voltrap" Transient Voltage Suppressor
RE: "Voltrap" Transient Voltage Suppressor
RE: "Voltrap" Transient Voltage Suppressor
RE: "Voltrap" Transient Voltage Suppressor
MOV's subjected to frequent spikes tend to lower in voltage over time. thread248-62476 Your design should not be subjected to frequent spikes (I assume), but keeping the voltage higher than you think may be the way to go. If you had sensitive circuits, transzorbs or some multi-component approach would be the way to go so you could clamp accurately at a lower voltage.
The device using the 256 volt device may had done it so they could be use with in a wider range of applications, or to insure they could intermittently survive a high voltage situation such as an open neutral. Sometimes the approach of transient supression is to take the top off the transients and not to try to protect for the over-voltage situations. If the purpose is to protect from overvoltage, then high-power clamping with an inline fuse might be used. The designer of this 256 volt device may have not had that kind of protection in mind.
Without more information of what you are trying to protect, what the damage threshold of the devices on your 125 VDC power, and how likely a transient situation is in your application, it's a little hard to give specific suggestions. But, I would think a MOV with clamping in the range of 160 to 220 VDC might be what you would want.
RE: "Voltrap" Transient Voltage Suppressor
As for the recomendation I got for the 256V AC MOV I found out that is used in a device that can operate on many voltages up to 220V AC. That makes much more sense now. I do agree that something in range of about 180-200V DC makes good sense. I appreciate the help.
RE: "Voltrap" Transient Voltage Suppressor
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RE: "Voltrap" Transient Voltage Suppressor
Shud d d e r :(
RE: "Voltrap" Transient Voltage Suppressor
This equipment sounds like it should be in an ExD (flameproof) or ExP (pressurised) enclosure if it is spark-generating and within a hazardous area. As I understand the haz area regs in the UK - and probably the rest of the EU - prosecution under the ATEX legislation allows individuals to be prosecuted as well as companies and their directors. I'd be thinking long and hard before doing anything questionable in a haz area from a personal liability point of view, quite apart from the prospect of it going ka-boom one day.
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RE: "Voltrap" Transient Voltage Suppressor