What is Unbalanced Voltage and Current Unbalance?

When you are running an industrial plant, the term “time is money” is incredibly true. The more efficient and productive you are, the more money you will make. In order to be producing at all times, or during all business hours, you need a lot of machines humming away. That means a lot of electricity. If you don’t feel your machines are working to full capacity, this electrical component may be to blame. The electrical power issues that most frequently affect industrial plants as yours include:

1. Voltage sags and swells
2. Harmonics
3. Transients
4. Voltage and current unbalance

You’ll want to pay close attention to number four- voltage and current unbalance. You see, in a balanced three-phase system, the phase voltages should be equal or very close to equal. “Unbalance” is a measurement of the inequality of the phase voltages. Voltage imbalance is the measure of voltage differences between the phases of a three-phase system. It degrades the performance and shortens the life of three-phase motors.

The impact of this on your machines’ motors can be severe. Motor winding insulation can break down. This leads to downtime, which is costly in and of itself, as well as potentially expensive repairs or replacements years before you should have needed to buy a new one.

As stated above, an unbalanced three-phase system can cause poor performance or premature failure. It is typically the result of one of the following:

1. Mechanical stresses in motors due to lower than normal torque output
2. Higher currents in your motors than what is normal
3. Unbalance current will flow in neutral conductors

Thankfully, there are tools that can be brought in to help you identify and then rectify the situation. Transient voltages, which are the temporary unwanted spikes or “blips” of voltage in an electrical circuit, can come from any number of sources. These could be either inside or outside of your industrial plant. Adjacent loads turning on or off, power factor correction capacitor banks, or distant weather like a lightning strike can generate transient voltages on distribution systems. Finding the source of these transients can be a challenge. After all, the frequency of the occurrences and the fact that these symptoms can present themselves in different ways means you’ll have a difficult time figuring it out without the right equipment.

You don’t need to figure it out alone! It is recommended that you identify and measure transients by using a three-phase power quality analyzer with a transient function. The transient function on the meter should be set to greater than 50V above the normal voltage and so the display will then show the potentially problematic voltage above 50V – the transients. If no transients are found in an initial measurement, it is a good practice to measure and log the power quality over time with an advanced industrial power quality logger. It may be only infrequent blips causing the issue.

The best way to handle this situation is to rent your needed power quality analyzer and use it over a period of time in order to find the source of the electrical problem. When you get your much-needed power testing equipment through PowerSight, we give you this option!