Using contractor

Thread Starter

Babu Mistry

Joined May 25, 2019
10
Hi I need to know regarding single phase motor wiring, using a contractor and puss button switch.
will it help when power supply from mains cut off and when it comes back will it start the motor or I will have to restart.
Anyway, I need is when I switch on the motor and when Power cut off, from the main meter it should not start. I have to restart my self.
Anyone who can help on this.
Lofty.
 

Dodgydave

Joined Jun 22, 2012
9,444
No using a Contactor with a Push button will Not Re energise when the mains is restored, you will have to press the button again, this is a safety feature..
 

SamR

Joined Mar 19, 2019
2,574
Wiring a motor starter for pushbutton start used a contactor output pair as a seal-in latch to continue running the motor when the button is released. During a power outage the contactor loses power and the seal-in latch is opened and cannot be remade until the power is restored AND the button pushed to start again. However, if it is switch operated, the motor WILL restart on power restore if the switch is still closed. Square D (Schneider Electric) used to have a great freebie book available on motor starter circuits that may still be available somewhere on the internet. Aha! Found it!
https://download.schneider-electric.com/files?p_enDocType=Catalog&p_File_Name=0140CT9201.pdf&p_Doc_Ref=0140CT9201
 
Contactors have what's called a NO (Normally Open) "aux contact" which is sometimes optional. This is a low current contact who's job is to maintain the coil current after it has been momentarily turned on. The NC switch in max's diagram momentarily interrupts power. CR is the aux contact.

A lot of times there is a multi-position switch labeled Hand/On/Off. Hand uses the start/stop buttons.
 

MaxHeadRoom

Joined Jul 18, 2013
21,415
One more thing is if using a 3ph contactor that has overloads, it is customary when using it for 1ph motor load, is to loop the live power motor conductor into the first top and loop out the bottom of the 1st O/L to the top of the second input, out of the bottom to the top of the third input etc.
IOW, occupy all contacts and O/L's.
Max., .
.
 
Top