How to Select a Hook-Up Wire or Cable

MISUMI is the leader in product selection and availability.  With millions of parts available on our website, MISUMI has a product to fit nearly any project.  Sometimes, the vast amount of available parts makes it difficult to find the one you need for your project.  Since a quality machine requires quality equipment, selecting the right kind of wiring is vital.

This guide will help you learn how to select a hook-up wire or cable to use in your automation equipment.

Selecting Voltage

First it is important to understand which type of voltage you are using – alternating current (AC) or direct current (DC).  The value associated with these (110 VAC, for example) is simply a measure of the potential available.  If we think about this in terms of plumbing, it is like a measure of the water pressure in a line.  The higher the pressure, the greater the potential – the higher the voltage, the greater the potential, as well.

In North America, electricity is supplied as 110 VAC, 208 VAC and 240 VAC most commonly.  Larger facilities such as manufacturing plants, typically see voltages as high as 480 VAC coming into the building.  This is then reduced to a manageable 240 VAC or even 110 VAC.  It is important to choose the right wire or cable for the voltage used in a machine for several reasons, including:

  • Wire thickness plays a big role in resistance; more resistance creates more heat, so the wrong gauge of wire can create potential safety and fire hazards
  • Over long distances, voltage in a wire can drop, so it is important to select a cable that will either reduce this likelihood or ensure it has not dropped below a usable level

To learn more about other factors to consider when selecting electrical wiring, see U.S. National Electrical Code NEC 240-3.

Selecting Amperage

Electric current is the flow of an electric charge.  This is measured in amperes and is what an electric device uses as power.  To continue with the water analogy, current would be the actual water flowing through the pipe.  If you have a large pipe with little pressure (voltage), then the water will only trickle out.  If you were to increase the pressure, then you will push much more water through the spigot.  This is how current works in the electrical world.

When considering which wire to use it is necessary to know how much power will be drawn by all devices.  For example, if a PLC is using 300 milliamps (mA) and the rest of the systems are using a total of 1 additional amp, then selecting a 4A cable will be enough. 

If a wire or cable were selected that is less than what the system is using, issues could arise such as overheating and the cable potentially melting.  Overloading is also a concern in which too many devices may be plugged into the circuit.  In these cases, a machine will not function properly as circuit breakers can trip and shut down the equipment.

Wire Gauge

One standard for wire is American Wire Gauge (AWG) designed to provide dimensions of bare / stripped wire.  An increase in gauge equals a decrease in diameter.  Another way to measure wire thickness is by the surface area indicated in mm2.  MISUMI provides a quick reference chart at this link.

Referring again to the water analogy, wire gauge would be the inside diameter of the pipe.  If you have a certain volume of water that you need to move through the pipe in a minute and cannot change the water pressure, then using a wider pipe will ensure the job will get done.  Similarly, larger diameter wires are used when more current must be carried through the circuit.  Since current moves through the wire more easily without voltage drops, longer wires can be used in the system.

Insulation

Besides isolating that power supply from another conductor including being grounded (a person, buildings, equipment and earth grounding out itself), insulation must be capable of continuously withstanding many factors. Considerations include exposure to environmental agents such as oils, chemicals, moisture, voltage itself including spikes and self-induced voltage referred to a counter EMF, temperature of environment, submergibility, bendability, and environment disposal concerns or toxic products if a fire occurs. Composition of insulation also effect expected life of wiring products.

Many wires use a standard PVC material as insulation to protect the conductor from scratches and shorts.  In high heat applications, PVC may melt.  In these cases, it is necessary to use a more robust insulating material such as fluorine or silicone.

UL Standards

Wiring can have a certification by a testing laboratory for meeting specific defined standards of a product through testing representative samples by an independent testing laboratory – one of which is Underwriters Laboratory (UL).  UL certification or listing is confirmation that the product conforms to UL applicable requirements including safety standards along with other organizations including possible government requirements.

Machine Tool Wire (MTW) is available in a large array of materials, conductors, voltages and environmental features such a flame retardance standards along with flexibility and resistance to oil and heat.  Electrical shielding is especially important in factory automation with PLC equipment as wiring not shielded in metal conduit or a metal housing are potentially exposed to electromagnetic interferences.  This can come from a variety of sources such as handheld radios, cell phones, electrical welding operations in the area.  It is wise to understand all the factors the cable will be encountering to select the various features needed for durable and safe operations.

Similarly, Appliance Wiring Materials (AWM) are used to connect factory automation equipment to control panels such as switches, sensors, electronic components, motors, lights, etc.  Some of the wiring is low voltage / low current such as for operating miniature LED indicator lamps while other lamps for example – heat lamps would certainly require heavier gauge wire like ordinary plug-in lamp cord.

Material Length

When determining which wire to use, distance can be an important factor because of the potential voltage drop.  In longer wiring distances (over 100 feet) there are voltage drops that occur, some factors to consider for electrical wiring see U.S. National Electrical Code NEC 240-3.  Wire size calculators are available online for properly sizing wire gauge requirement that include core material – copper or aluminum, source voltage, phase, amperage demands and distance. Some calculators may include type of insulation information, method of installation such as buried in earth, open air, raceway or conduit.  One calculator takes ambient temperature into account. Regarding voltage drops – Ohm’s Law calculations provide proof when the resistance (load) remains the same, supply voltage drops, the resulting equation results in higher current draws.

MISUMI strives to be the leader in hook-up wire and cable.  Our website offers a large selection of products that can fit any application and budget.  In many cases, we offer these wires cut to a specific length, so you do not need to worry about ordering more cable than is necessary.  Check out our website to learn more about how MISUMI can help with your wiring needs!

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2 Comments


  1. Lloyd Bridges

    August 22, 2019 at 1:32 pm

    I’m an experienced electrical engineer working on a new project. I need to design and source a cable assembly which will combine several signals (5V power, AC power, stepper motor control signals (4 signals each approx. 3A @ 10V). The cable assembly needs to be enclosed in a “jacket” so that it can be attached to a mechanical guide which is moving over rollers and pulleys. How can I start looking at your website to learn more about combining a set of cables in this way?
    Lloyd Bridges

    Reply

    • Carlicia Layosa

      August 22, 2019 at 1:45 pm

      Hi Lloyd,

      A member of our electrical team will get back to you ASAP!
      Meanwhile, I would recommend to check out our cables at this link.
      Thank you!

      Reply

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