OK Guys Thanks &Sorry for the slightly confusing diagram.First of all, you will not get 12 volts DC from the transformer shown. You will need s rectifier also, or you can use a 12 volt DC power supply.
Now some questions, the first is if this is intended to replace the current arrangement or to be in addition to the present controls arrangement? The second question is will there be the possibility of unsafe operation if the stop button fails to switch off the motor power? The circuit shown has both controls connected.
The circuit arrangement shown will not work if the motor control starter coil is that symbol with the "M" in it, because that is in series with the 12 volt relay coil, and it is not safe because the stop portion will not function if a wire becomes disconnected.
And it looks like the circuit is made with single-pole automotive relays and door bell buttons, which are really not OK for controlling a 480 volt motor.
A good motor control will use a normally closed button as the stop control. And in this case the circuit would be simpler.
Often AC powered relays run cooler, which can be a benefit. And there are fewer components to fail. High voltage lie spikes that destroy diodes cause no problems with AC circuits, usually.From my experience, you would be better off to fit a small bridge rectifier off of the 12vac and use DC relays, also it is far better and clearer to use ladder logic schematic rather than the form you are using.
As @Alec_t asks, what is the 'M' in series with a relay coil?
You already show 12vdc, just the bridge is missing.
But basic electronic/magnetic principles still apply.So DC solenoids can be fine for solenoid applications, much different from relay applications.
ZERO down time from any AC powered relay or contactor in the past 35 years tends to indicate that the quality of the components matters quite a bit. Allen Bradley 700N series control relays seem to have been good choices. Not cheap, but they do have a tendency to keep working.But basic electronic/magnetic principles still apply.
I have spec'ed in DC for relays and solenoids since the mid-80's, also now that industrial control circuitry has primarily moved away from 120vac to 24VDC, it is easier to implement the DC versions, also many P.B. indicator devices etc, are LED illuminated which also goes better with a 24vdc control circuitry.
For one custom machine that was made in the USA for a customer of mine here who had asked me to specify electrical recommendations in the design, I had stipulated the 24vdc rule for all magnetic devices and control, resulted in some protesting in the form of "We have always done it this way"! (120vac).
The customer preferred the lower down times in production!
OK, I had not considered that the remotes would be plug-in types. My design was for wired in remotes, mostly because I have seen that anything that can be unplugged will vanish eventually, at least in the areas that I have worked.OK Thanks,
The reason that I have used NO Swiches for the stop circuit is so that if a remote is unplugged the system will still work. I could, if I remove the running light and make the system require all switches to be plugged in at all times, simply wire a series of 3 NC switches to a relay (NO) coil and have that break the 240V system in series with the integral Stop Button. Then have the 3 Parallel wired NO starter switches activate another (NO) relay Coil to switch on the 240V in parallel with the starter button.
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