Temperature kills electric devices. It has a bad effect on cables, motors, transformers and al electrical devices. In this article I will discuss How does Temperature affect electrical equipment?
How does temperature affect electrical conductivity?
We know that metals are great conductors of electric current because of the free electrons present.
When you increase the temperature, electrons’ motion increases, which causes unintentional collisions, resulting in an increase in resistance in the metals,the electrons’ mobility reduces, which causes a lower conductivity.
In other words, the conductivity of an electrical wire or cable will diminish as increasing temperature!
All this implies that when you use a cable you should derate its current depending on its working conditions. Of course, environment or ground temperature is one of the derating factors of cables.
You should apply temperature derating factor to make sure you have the right cable for the load.
I’ve written a detailed article about Cables Derating Factors, I highly recommend reading it for more information.
How does temperature affect resistance?
The rise in the temperature of the conductor increases its resistance and decreases its current capacity.
The free electrons that move around the metal conductor collide with each others, generating heat; the collisions increase as the metal conductor generates more heat.
They create obstacles to the conductor’s electrons’ further movement and cause more resistance. Thus, the increased temperature of the conductor will increase resistance within the conductor.
Resistance is usually an opposing force to the body’s movement and reduces the body’s ability to perform. For example, in the field of electricity, it is the resistance provided by the material against the flow of electricity through it.
The conductor‘s resistance will vary based on various variables, including the material used to construct the conductor that makes up the conductor’s dimension, the ambient conditions, and more. Temperature is also a crucial element that alters the conductor’s resistance.
As I just told you above, using electrical cables in hotter environment or soil, reduces its ampacity. That’s why we derate its current.
How does temperature affect wires and cable?
Temperature is an essential concept to comprehend. If something’s too hot, it will melt or catch fire; when it gets too cold, it will freeze or break.
Read also my other articles: Motor temperature rise causes and effects.
Affect of hot temperature on wires and cables
Cable temperature rise causes its resistance to increase, ampacity to decrease and causes its insulation to melt down. If the insulation melt down,a short circuit can occur.
In case of overhead power lines, wires expand in summer days making wire sag. However in cold days this sag shrinks and wires become shorter in length. It’s essential to take this sag into account when installing the OHTL.
Hot temperature can cause cables to become over heated. Remarkably, it raise the resistance of wires, making an electrical wire less efficient.
The cable’s insulation can withstand thermal stress also. The insulation could melt and cause electrocution or fires. If the cable doesn’t possess the proper temperature rating, it can occur during the extremely hot summer months.
But, the consequences of excessive heat are particularly significant in the industrial environment that places cables exposed to extreme temperatures. In these instances, only the cable has an insulation type capable of withstanding extreme heat that can function.
XLPE insulation can handle higher temperature rise than PVC insulation, this enables XLPE insulated cable to have a higher ampacity.
For more information about Cable insulation PVC an XLPE read my article here.
Affect of cold temperature on wires and cables
Yep, cooling the cables down increases its ampacity. But, there is limits, cables have temperature limits to work efficiently.
Cold temperatures, particularly the highly frigid winter temperatures, can be detrimental to cables. They result in conductors of cables losing heat, which affects the performance of the wires. The main factor that affect cables current carrying capacity is its temperature.
Another weakness regarding cables in colder temperatures is that lines are becoming more rigid to the point of breaking.
Setting up electrical cables in cold winter months can be challenging, and it is not recommended. In addition, certain kinds used for cable insulation like PVC, which is the most common type of PVC, might become stiff due to the force of cold temperatures.
In case of overhead power lines, wind sagging and ice accumulation are frequent issues that can lead to wires cut. But, like the heat, careful and prompt management by utilities is the most effective solution.
Overhead power lines in my work face the issue of sagging in winter cold days. Wires strength in winter causes it to cut.
How does temperature affect electric motors?
If the temperature inside the motor is higher than the value of its insulation class, the insulation breaks down and the motor may burnout due to internal short circuit.
If the temperature rise is not enough to burnout the motor, then the rise in temperature affects the motor’s lifespan. Therefore, while operating, ensure not to exceed the allowable winding temperature. I have written a detailed article about motor burn out, You can read it here for more information.
As the winding temperature within the motor is not determined directly, you must measure the temperature outside of the motor’s body to examine for a reference.
For more information about motor temperature rise, read my article here.
What causes motors to overheat?
If you’re concerned about the rise in temperature within the machine, examine the surrounding environment. These are some factors that cause the excessive temperatures of motors:
A motor that is not suitable: Motors is available in various sizes. Select a motor that can handle the load power.
Incorrect voltage supply: Under and over voltage could harm motors. Over voltage causes the motor to burn out due to insulation failure.
While under voltage cause the motor to draw more current and overheat, then burnout.
Poor cooling: Motors require enough airflow to cool it down, so it can function optimally. If the motor operates in a hot, humid climate, it’s likely to struggle to cool down fast. Make sure that the motor has plenty of space to run.
Make sure the motor cooling fan is not broken and the cooling ventilation is not blocked.
Improper Use: Some motors may be run continuously, while others are designed in intermittent intervals.
It is essential to utilize your motor under the specifications of the motor. If you attempt to operate an infrequent duty motor for too long, the motor will not get cool between cycles.
Read my article about motor duty cycle here.
Altitude: Your location and the area of your business will affect your motor’s performance. Your motor may not cool as well in higher elevations since the air density is lower. It’s crucial to select a suitable motor for the location of your workplace.
An absence of ventilation: If something is blocking the vents for your electric motor, the hot air can accumulate, which can cause harm.
Making sure you schedule regular maintenance for your motor may reduce the chance.
Can electric motor work in low temperature environments?
When temperatures are lower than -20° C or higher than 40° C, you need to take extra care of components such as grease, bearings, seals, fans, insulation or leads. They’re among the most frequently encountered issues of running electric motors in hot and cold conditions.
Overheating could occur when ventilated motor enclosures are covered with snow or ice. It can be caused by an overload condition. The operator needs to ensure that they adhere to the motor’s operating guidelines as usual during colder weather.
Cold weather is also a cause for concern regarding the safety of Class I explosive-proof motors. The pressure to ignite combustible gas tends to be greater at colder temperatures.
Flame paths and enclosures that are explosion-proof should stand the increased pressures associated with a cold environment.