Mr. Spinosa
Member
- Location
- Tacoma, Washington, USA
When working with motor controls, why would you put a momentary stop on only one phase conductor? - How could I explain that it is okay to disconnect only one phase?
Joe I don't think he wasn't talking about the feed to the motor but the start stop control, common to motor starters.
The reason you only need to momentary break the connection to the contactor coil is the basic operation of a start stop circuit, the coil of the motor contactor is a single phase device and only has two wires to it, one from the over loads from L2, and one from the start stop circuit, the start stop circuit has L1 running to one side of the stop button this button is a NC contact and makes contact until pushed inwhich it opens, the other side of the stop button runs to the start button which is a NO which closes when pushed, from the other side of the start button it goes to the coil, if this was all there was pushing the start button would only pull in the contactor while it is being pushed, so we have another set of NO contacts on the contactor in parallel with the start button, that when we push the start button the contactor pulls in and closes these auxiliary contacts locking the motor contactor on, this provides power to the coil through the stop button through the aux contacts to the coil, now when you push the stop button, it disrupts the current to the coil dropping out the contactor and opening the aux contacts, this stops the motor because the motor contactor disconnects 2 or 3 of the phase conductors feeding the motor.
Also the over loads each have a NC contact that when they trip they will also drop out the motor contactor and shut down the motor.
Look for a diagram on a start/stop circuit.
How about before we go to far we wait for the OP to let us know what he means?
It could be a single phase motor he is talking about and the code allows controlling it by one leg only.
No, but there probably is a 12 step program available for it.OOPs,
How did I miss that he didn't say 3 phase?????:slaphead:
I think I must have an injection braking obsession. I wonder if there is a drug for that.
How about before we go to far we wait for the OP to let us know what he means?
It could be a single phase motor he is talking about and the code allows controlling it by one leg only.
No, but there probably is a 12 step program available for it.
A three phase motor controller only needs to open two legs and does not have to open all three BTW.