1. Two wire control means, two wires for drive start command of "Forward and Reverse". In two wire control there is no separate stop command is provided. The forward and reverse command is given through switch, so if the run command is high - the drive will run. If the run command is removed - the drive will stop. The circuit will be as shown in picture below.
.png "Two wire control")
2. Three wire control means, one wire for stop command ("NC" Pushbutton) and two wires for drive start command of "Forward and Reverse("NO" Push button)". In three wire control, the stop command is provided separately. The forward and reverse command is mostly given through NC pushbutton, however RUN command can be given though switch also, if auto restart is necessary. In three wire control, first the stop command should be high. After that if the run command is given(high) - the drive will run. If the run command is removed - still the the drive will be running. The drive will stop only when the stop command is removed. The circuit will be as shown in picture below.
.png "Three wire control")
In both circuits shown above, the reverse command can be ignored if not necessary for the application, still the same circuit is applicable for 2-Wire and 3-Wire control. It means, if the stop command is provided separately, it is called 3 wire control and if separate stop command is not provided separately, it is called as 2 wire control.
Released for:Schneider Electric South Africa
