What are the advantages of a DC Motor versus an AC Motor. I've got two old conveyors I'm going to begin to rebuild in the next few weeks. I am going to replace the motors during the rebuild of course.

The conveyors originally came with DC motors and I'm thinking that converting to an AC motor requiring no brush maintenance might be a good idea or it might not.

I would be willing to install a freq drive to control speed. Should I match up HP and go for it, or would you guys just stick with the DC motors. What are the advantages of a DC motor?

Thanks!

How reliable are Ross air valves? Is it worth tracking down exact replacements and rebuild kits, or should I look for retrofits? Thanks in advance.

Folks,
I have been haunted by a vintage DC motor starter. It consists of a series of contactors, a resistor bank, some vintage timers, and a lot of old wiring. It is the starter for a 240VDC motor at 75 HP.

There is a ghost in the system. Most of the time it starts appropriately, and sometimes it just won't start the motor. I started checking the coils for resistance and noticed that one of the contactor coils that steps through the starting resistors has a lower resistance reading than the other two.

My question is if the contactor is closing, would the lower resistance have any effect of the rest of the sequence?