Electrodesalination transformer, DC voltage, 4-20mA
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In a project, it is necessary to convert the DC output voltage of a transformer used for DC desalination into a 4-20mA signal to be sent to the DCS; this transformer was manufactured by Shenyang No. 4 Transformer Factory. The DC voltage range is 0-25KV. No suitable voltage transmitter is available on the market. I later consulted the manufacturer, who said that the original high-voltage DC voltage should first be converted to 0-500mA, and then the digital ammeter should be used to transform it into a standard 4-20mA signal. The problem now is how I can convert 0-25KV DC to 0-500mA. I would like to know what approach is used by other users with similar devices?
Our plant uses DCS to monitor the voltage of 0-50KV in the electrostatic precipitators. There is a circuit board inside the rectifier transformer that can convert the direct current high voltage into a 0-10V signal, which is then converted to 4-20mA using a signal converter. A few months ago, we replaced a circuit board of this type in our factory; it had many resistors on it. You can ask the colleagues in the electrical department and they’ll know! This post was last edited by liuei on 2009-4-10 23:56.]
I asked a friend who works in the electrical field, and he said that Wuhan Huatian Power Automation Company might have the high-voltage measuring instruments you’re looking for. You can give them a call at 027-87492243 to ask. If they don’t have what you need, you’ll have to modify their digital high-voltage meters yourself! Digital headers usually have an input of 1V or 2V; this signal can be converted to 4-20MA, after which it can be fed into the DCS! This post was last edited by liuei on 2009-4-11 15:19]
There is a voltage-dividing plate inside the transformer; that’s correct. Every rectifier transformer should have such a voltage-dividing plate, as it is from there that the controller obtains the signals. Take a close look at the controller diagram; by extracting this signal from the controller and converting it, it can be fed into the DCS!
Thank you for liuer’s generous help. The transformer’s diagram shows only a voltage-dividing resistor; there is no other parameter information provided. I don’t know what the ratio of this voltage division is, and it can be seen that a voltage signal is generated as a result. But when I asked the manufacturer, they said it’s done by measuring current (0-500mA). So can we just insert a resistor in series? If that’s the case, it would be better to simply measure the voltage instead. There is really very little information available from domestic manufacturers.
There’s no more detail available; it’s a AC/DC desalination transformer produced by Shenyang No. 4 Transformer Factory, and the user can’t even find a manual for it. It’s not available on the manufacturer’s website either. Website: http://www.csysb.com.cn/newEbiz1/EbizPortalFG/portal/html/ProductInfoExhibit.html?ProductInfoExhibit_ProductID=c373e90831a224e88f6f7fddce617058&ProductInfoExhibit_isRefreshParent=false. The V+ and V inside-