Power resister problem

Hope someone can help. I have a PLC that went down. No power past the 120V (L1) supply terminals. I have what looks like a power resister out with a complete open across the leads. the data on the device is as follows-

ROC 135F
10R0(then the omega sign)5%
H0247-1

I2 anyone familiar with this brand of device?

The 10R0 usually means 10.0 ohms at 5% tollerance.

I would get a 5 watt or about the same physical size 10 ohm resistor and try it.

Thanks LeadFoot, I'll try it. I was just guessing that it was a power resister. I have had several PLCs do this in our plant. Any idea why?

That sounds like a fusible resistor. Find more info on it if you can.
If it is a fuse, then line surges are probably taking them out.
Do not use a standard resistor if this is a fuse!

I have had several PLCs do this in our plant. Any idea why?

Click to expand...

We added sola constant voltage transformers to cure problem like this and many others. The bigger ones are pricey, but if you at least power your 120vac electronics (PLC, HMI, PC) it will pay for itself by eliminating downtime caused by replacing power supllies, fuses, etc.


Our voltage can go from 460 to 510 when much of the equipment is down. Even when we manage the capacitor banks, problems occur like drive overvoltage faults etc., but with the sola CVT, the secondary control voltage is a steady 120v. Our plant only shuts down a couple of times a year. Before we had the CVTs startups were hell when you had three or four (of 100) HMIs dead, and ten or twelve fuses/breakers blown. You know the story...

Just my 2 cents

I have seen many boards that have a 5 or 10 ohm resistor on the input with a 5 to 10 uf filter cap across the input for filtering. I have seen many of these resistors burn out over time due to trashy line voltage. Even "SUPPOSEDLY" clean DC supplies.

I heartly recommend the SOLA transformers. SSSSOOOO many times I have seen really nice surge suppression and line filters at the input to PLC's fry from the noise on the main line caused by drives. A SOLA is a worthwile investment as it TOTALLY removes the trash and the PLC's and HMI's no longer have any issues.

In the equipment I have been testing the last couple of weeks, I noticed the engineer began to use 230 in and 120 out rather than 120/120 like we did previously. I noticed the SOLA was less noisy when one of the 1800 HP DC drives was running.

One note on the SOLA constant voltage transformers. The do work really well for getting rid of noise and, to a certain degree, brownouts. But the way the work is by operating really close to the magnetic saturation point. That means they have very little headroom for ouput current surges. We replaced a standard 120 VAC transformer on one of our machines with a SOLA constant voltage transformer of equivalent power rating. We started having trouble when contactors in the control circuit fired. Yes, we should have used the transformer to only power noise sensitive loads. But we thought that, since it had the correct power capacity, we would be OK with a direct swap. We weren't.

I do recommend the SOLA units. Just be a little carefull about sizing and/or what you power with them.

Keith

I'd recommend SOLA products too. We've been using their transformers & power supplies regularly.

http://www.clrwtr.com/Sola-Hevi-Duty-Transformers.htm