Indicator light bulb 30V

[SLK001]

Mark, does the transformer supply 24vac for other components (and not just the power indicator lamp)? The question has already been mentioned above but not answered yet.

It probably powers a control board, but the AC is rectified, then regulated to a set voltage. A little over on this input won't hurt the control board at all.

Some of the first automotive LEDs I have used did not last long and I have wondered why ever since.

The LEDs didn't last long because there were too few in the package and the ones that were there were over driven. It's like having to run a 100 HP engine at 150% output for its entire life - which will be short.

 

[mksj]

The AC is not rectified, the contactors are AC and will not run off of DC. Low voltage 24VAC is used for the control system, power to the front panel and spindle switch that then activates the contactors. The 24VAC voltage will fluctuate based on the load, contactors closed will draw more current. I am assuming KA is the main power contactor, KM1 and KM2 are the motor run in the respective direction. Transformers do not give a fixed output, their unloaded voltage can be much higher than loaded, varies by design and also the VA of the transformer. As far as how long LED last, there is a big difference in the quality and the design of the LED's and also if there are multiple LEDs or just one. With multiple LEDs in one lamp, you often see a cascade effect, one fails and then the remainder draw more current, and then the next until they all burn out. Ironically when I buy say a Philips brand LED lamp, I have yet to have one fail, the cheaper brands, in particular the junk on eBay often fail much sooner. I have also seen similar issues with the incandescent indicator bulbs, I often will source NOS like GE and they function correctly. I have measured the current, the newer lamps draw more current and shine brighter, and do not last. Reason why I mentioned just going with a decent brand LED indicator light after all the headaches you have had.

The transformer looks like it is around 63VA so around 2.6A, but is fused for 1A (FU3).

 

[Tozguy]

Thanks for the explanations. If I understand correctly the system is not all that sensitive to normal voltage fluctuation. The change I made to the transformer input, that likely improves the life span of the indicator lamp, would not create problems elsewhere in the system. By lowering the output voltage from 27vac to 24vac, current draw might increase proportionally but it should still be within the limits of the 24v fuse.

I did not realize that there are fuses in the system. Are these like breakers and can be reset or would they need to be replaced if they burn?

 

[mksj]

Your system is designed to operate at 24V AC, not the higher voltage. Cnntactors operate at a specified voltage but will operate over +/- voltage range. They will probably operate from 20-28V AC (+20%/-10%), but depends on the contactor/relay and coil. Too low a voltage and the contacts may not fully close or chatter, too high (or too low) may cause premature failure. You have three fuses (not breakers), most likely FU1 and FU2 are each leg of the 120VAC going to the transformer, and as mentioned FU3 is one leg of the 24VAC output (only one side needs to be fused). These are fuses, the fuse holder typically swing out or pull out and you would need to use a fuse of the same style an amperage (1A). Should not need to replace the fuses unless there was a wiring short/overload.