Definite purpose contactors are electrically operated switches that are used to control electric loads such as motors, air conditioners, heaters, and other electrical equipment. These contactors can handle high electrical loads and are specifically designed for particular applications. The following article will discuss the wiring diagram for definite purpose contactors.
What is a Definite Purpose Contactor?
A definite purpose contactor is an electrically operated switch that is made to control a specific type of load. These contactors are typically used in commercial and industrial applications where the loads are high and need to be controlled accurately. Unlike general-purpose contactors, definite purpose contactors are made with specific ratings and specifications to match the motor or load being controlled. This makes them more reliable and efficient.
Definite purpose contactors are used in a variety of applications, such as:
| Application | Contact Rating | Usage |
|---|---|---|
| Motors | Up to 600VAC and 60A | To start, stop, and change the direction of motors |
| Heaters | Up to 480VAC and 60A | To control the temperature of heaters |
| Air Conditioners | Up to 600VAC and 30A | To control the compressor and fan motors in air conditioning systems |
Wiring Diagram for Definite Purpose Contactor
The wiring diagram for definite purpose contactor consists of the following components:
- Power Supply
- Contactor
- Thermal Overload Relay
- Load (Motor, Heater, etc.)
The power supply is connected to the contactor through the control circuit. When the control circuit is activated, the contactor closes, allowing the power to flow through the load. The thermal overload relay is connected in series with the load to protect it from overloading and overheating.
The wiring diagram for a definite purpose contactor is as follows:
| Component | Wiring |
|---|---|
| Power Supply | Connect the incoming power supply wires to the L1 and L2 terminals of the contactor |
| Contactor | Connect the load wires to the T1 and T2 terminals of the contactor |
| Thermal Overload Relay | Connect the thermal overload relay in series with the load wires at the T1 and T2 terminals of the contactor |
Example Wiring Diagram
Here is an example wiring diagram for a definite purpose contactor controlling a motor:
In this example, the power supply wires are connected to the L1 and L2 terminals of the contactor. The load wires are connected to the T1 and T2 terminals of the contactor, which are then connected to the motor. The thermal overload relay is connected in series with the load wires to protect the motor from overloading and overheating.
Frequently Asked Questions (FAQ)
What is the difference between a general-purpose contactor and a definite purpose contactor?
A general-purpose contactor is a type of electrically operated switch that is used to control a wide range of loads. These contactors have general specifications and ratings and can be used in a variety of applications. A definite purpose contactor, on the other hand, is specifically designed to control a particular type of load. These contactors have specific ratings and specifications that match the load being controlled, making them more reliable and efficient.
What is the purpose of the thermal overload relay?
The thermal overload relay is used to protect the load (motor, heater, etc.) from overloading and overheating. When the load draws too much current or operates for too long, the temperature of the load increases, which can damage the load. The thermal overload relay senses the temperature of the load and disconnects the power supply if the temperature exceeds the set limit.
How do I select the right definite purpose contactor for my application?
To select the right definite purpose contactor for your application, you need to consider the following factors:
- The type and rating of the load (motor, heater, etc.)
- The voltage and current rating of the load
- The type of control (manual or automatic)
- The environment (indoor or outdoor)
Based on these factors, you can select a definite purpose contactor that matches the specifications of your load and application.
Can I use a definite purpose contactor for a different type of load?
No, you should not use a definite purpose contactor for a different type of load. Definite purpose contactors are designed to control a particular type of load, and using them for a different type of load can result in damage to the load and the contactor. Always use a contactor that matches the specifications of the load and application.
Do I need a thermal overload relay for my application?
It depends on the type and rating of the load you are controlling. If the load has a high current rating and operates for long periods of time, a thermal overload relay is recommended to protect the load from overloading and overheating. If the load has a low current rating and operates for short periods of time, a thermal overload relay may not be necessary.
