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OT- question relating to DC shunt motor schematics
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On the schematics pertaining to DC shunt/series motor starters, is there any naming convention relating to L1 and L2 being positive/negative?? I ask because I'm used to DC systems specifying polarity, and the only "polarity" mentioned on the schematic I have is the name "D.C. Automatic Starter".
I'm cross posting on Tekscopes2, where any discussion should take place, and adding more info there. -Dave |
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In my 30 plus years in the elevator craft, I have never seen or heard of any standard of L1 and L2, and I have worked on many DC motor starter/reverser panels. Different manufacturers used whatever designation they wanted to, every print I ever saw made it clear which input terminal was to be positive and which was negative. Polarity is very important, large contactors have "blowout" coils or magnets, improper polarity can prevent the arc formed when a contact opens from being snuffed. A flashover between contacts is a sensory experience you will not forget! It is great to hear someone discussing old control gear, learning about it is vital for proficiency with newer controls, and there is a surprising amount of that gear still in use today.
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Bruce Gentry, KA2IVY International Union of Elevator Constructors, Local 62, Retired On 8/28/19 10:03 PM, Dave Seiter wrote:
On the schematics pertaining to DC shunt/series motor starters, is there any naming convention relating to L1 and L2 being positive/negative? I ask because I'm used to DC systems specifying polarity, and the only "polarity" mentioned on the schematic I have is the name "D.C. Automatic Starter". |
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Hi Bruce, thanks for the input!
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If I sent you a photo of the schematic off list, could you make an educated guess (or perhaps see something I've missed?).? I've read schematics since my Radio Shack 101 kit, but power control, especially 3PH, is all new to me.? Vintage makes it even more interesting.?? Regards, -Dave On Wednesday, August 28, 2019, 07:57:58 PM PDT, greenboxmaven via Groups.Io <ka2ivy@...> wrote:
In my 30 plus years in the elevator craft, I have never seen or heard of any standard of L1 and L2, and I have worked on many DC motor starter/reverser panels. Different manufacturers used whatever designation they wanted to, every print I ever saw made it clear which? input terminal was to be positive and which was negative. Polarity is very important, large contactors have "blowout" coils or magnets, improper polarity can prevent the arc formed when a contact opens from being snuffed.? A flashover between contacts is a sensory experience you will not forget! It is great to hear someone discussing old control gear, learning about it is vital for proficiency with newer controls, and there is a surprising amount of that gear still in use today. ? ? ? Bruce Gentry, KA2IVY International Union of Elevator Constructors, Local 62, Retired On 8/28/19 10:03 PM, Dave Seiter wrote: On the schematics pertaining to DC shunt/series motor starters, is there any naming convention relating to L1 and L2 being positive/negative?? I ask because I'm used to DC systems specifying polarity, and the only "polarity" mentioned on the schematic I have is the name "D.C. Automatic Starter". |
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Chuck Harris
It really doesn't matter. Because both the field, and the
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armature change polarity, when you change supply polarity, the motor will continue to spin the same direction. Back in the days of yor, when there were competing AC and DC power generation systems, a universal motor was imagined, that would run on either AC or DC equally well. It is just a DC motor with the field and armature in series or shunt. To reverse a series, or shunt motor, you have to swap the field connections relative to the armature connections. -Chuck Harris Dave Seiter wrote: On the schematics pertaining to DC shunt/series motor starters, is there any naming convention relating to L1 and L2 being positive/negative? I ask because I'm used to DC systems specifying polarity, and the only "polarity" mentioned on the schematic I have is the name "D.C. Automatic Starter". |
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Send it to me off list, I will help you all I can. Bruce
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On 8/28/19 11:28 PM, Dave Seiter wrote:
Hi Bruce, thanks for the input! |
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