If you’re looking to operate three-phase AC motors in applications such as conveyors, packaging lines and thread-cutting machines, a reversing contactor could be just what you need. Combining two standard contactors with a mechanical interlock unit, a reversing contactor allows for fast and demanding forward/reverse operation. In this article, we’ll explain what a reversing contactor is, how to make one, and the advantages of using one in your equipment. We’ll also provide power and control circuit connection diagrams to help you get started.
What is a Reversing Contactor?
The reversing contactor is a kind of special product that can be built by combining two standard contactors by use of a mechanical interlock unit. Reversing contactors are designed for demanding forward/reverse operating of three-phase AC motors.
Typical applications of these products are conveyors, thread-cutting machines, packaging lines, and other applications where fast reversing capabilities are needed.
To make a reversing contactor you will need two same types of contactors and an interlock device considering the power of the motor. These two same contactors and interlock can be factory mounted or can be selected separately. The interlock device will prevent the contactors from turning on at the same time. An interlock can be placed between two contactors.
Below you can see the power and control circuit connection diagrams of reversing contactors. Let’s explain how they work:
1-Wire up the first and second contactor’s coils to separate pushbuttons. The second pushbutton has one side jump to the other pushbutton’s power source and the second contactor’s A1 is jumped with the first contactor to reduce the need for an additional control power source.
2-Jump the wires on the line side that are the wires connected to the main power source. They should be the same on both contactors. So, jump L1 with L1, L2 with L2, and L3 with L3.
3-On the load side which are the wires going to the motor need to be jumped a little bit differently. T1 with T3, T2 with T2, and T3 with T1.
4-When the power is applied to the first contactor from the three-phase coming in, it will be jumped to the second contactor. When the second pushbutton is engaged, the coil actuates and the power will go through contacts. The power is jumped to the first contactor two wires swapped and then to the motor.
5-Since T1 and T3 are swapped with the power coming in, the motor will run in reverse.
6-Optionally, an emergency pushbutton can be used at the beginning of the control circuit to cut off all the energy.
Power circuit connection of reversing contactors
Control circuit connection of reversing contactors
M1= Forward contactor
F= Forward pushbutton
M2= Reverse contactor
R= Reverse pushbutton
o= Emergency stop pushbutton
Advantages of reversing contactors
Except for the reversing operation of a motor, reversing contactors are ideal for reversing motors in applications where panel space is a premium and device modularity is required to satisfy virtually any application requirement.
Reversing contactors consist of an assembly of standard contactors along with interlock & wiring modules, these are assembled in the form of direct application as reversing contactor and are to be used in a panel or an enclosure.
A common mechanical interlock, power wiring modules, and accessories will help reduce your total installed cost and enhance the features and performance of your equipment.