AQ: Pressure switch on three phase motor
Q: Is there a way of connecting a three phase pressure control switch on a three phase motor. Also is there a three phase float switch for a three phase submersible pump i know of a single phase switch.
A: The switch only needs to have a single contact since you use a three-phase motor controller to operate the motor. The switch is wired into the low voltage contactor coil circuit to turn the motor on and off.
You can connect a pressure switch for the purpose of motor control on its low level pressure or high level pressure. It is advisable to utilize pressure switch on the control cct, and connect the contactor coils through the auxiliary NC/NO contacts depending on whether you are interested on low pressure or high pressure control. It is not good practice to allow power cct through control ccts. You don’t need a 3 phase float switch to achieve controls of a 3phase submersible pump. You should be interested in the auxiliary terminals which will allow control flexibility for low level and upper level control. A single phase float switch will give you desired result. If you are controlling more than 1 no. 3phase motors located at different places from the same pressure signal, then your 3 phase pressure switch can be employed to control the different motors separately. In addition, some terminals could be used for indication/annunciation purposes. However, a single phase pressure switch can give you all the controls you need for a 3phase motor.
