How to Choose a Contactor for Compressors

Choosing a Contactor for Compressors
One important part of operating a compressor is selecting the right contactor; you want to make sure the compressor has the right protections, if you intend on keeping it that way! Compressors form an important part of a lot of our applications, and the right electrical protection device can increase the lifetrain of the compressor, and in turn the whole system. This articles considers what to look for in a contactor, when you are selecting one for a compressor; of course voltage ratings and current ratings are important, and also environmental.
What a Contactor is
Simply put, a contactor is a switch that you can use to switch on and off supply to very large loads, such as motors, or compressors. It is the link that sits between the low voltage circuit which commands the high voltage. Put simply, a contactor will allow you to switch a given compressor on and off, and thus then allow it to run to spec.
What to look for in your Contactor
Voltage and Current ratings
The first consideration we have to make conscious note of, when looking for a contactor to use with a compressor is to make sure that the voltage and current match.Compressors particularly require high inrushes of current so any device selecting this must be prepared for it.
Select a contactor whose rating is just above the maximum current, which may then be larger than the steady state current due to increased demand for current.
Inrush Current and Switching Capacity. Compressors draw a number of times their normal power circuit current when energized. has to be selected that will enable the contour to withstand the shock. Also check the contactor’s switching capacity, which signifies the maximum inrush current they can handle in normal motor starts.
Frequency of Switching. If, in use, the compressor is to be started and stopped frequently—common in some systems in their cycling on and off because of pressure conditions—and also normally started and stopped in industrial position control procedure, it is essential that contactors are rated high for switching cycles. Ashigh a mechanical endurance as possible should be selected to assure a long and satisfactory service.
Types of contactors for compressorseTwo varieties are usually used on compressorsthey are discussed here.
a. AC contactor. For HVAC applications on relatively low AC power ratingsthe refrigerant contactors, used for compressor motors, most usually use this type ofacontactor.
b. DC contactor.Environmental Factors
Environmental factors can also be a part of contactor selection, particularly for compressors that may be found in less than ideal surroundings.
Temperature: Compressors are often found in environments where the ambient temperature is something less than benign, so be sure the contactor you use on one is rated for that temperature, both hot and cold.
Humidity, dust, and corrosive materials: In cases where your compressor may be exposed to these nuisances, the IP (Ingress Protection) of your chosen contactor can come into play. For example, an IP65 rated contactor indicates that it has been sealed to provide the highest degree of protection against damaging substances, and so will be especially long lived in this kind of service.
Vibration: Should the compressor to which you intend to attach the contactor subject it to rough treatment while running, you would choose a contactor rated for that kind of duty so that it would operate reliably.
Durability and Reliability
“Durability” means the measure of the contactor life under continual operation, as an operating compressor would call for. “Reliability,” of course, needs no further mumbling explanation and is to be highly desired in the contactors serving compressors.
Cost versus Quality
It is tempting to go for the cheapest possible solution to the contactor problem, and we would never claim that this should be done at the expense of quality. While the initial purchase price of cheap contactors may make the decision overly simple, cheap contactors fairly catch fire in the field compared with their higher priced, better competition. Take the plunge and buy the best; it will save money in the long run.
Summary
Selecting the proper contactor for use in compressors is clearly going to be critical for efficient operation of the whole machine. Keeping the factors from the above list in mind, along with others learned by experience, one can guarantee smooth operation of the compressor just as it should. A good start is in fine selection of the contactor for the job.