The Ultimate Guide to Power Quality – Solve Problems Before They Happen

Posted by Glenn Bullion on

Introduction

Electrical power. It’s marvelous, but mysterious. And, because it runs just about everything in your plant, it’s also one of your major costs.

Poor power quality has become a very serious problem in many industrial facilities, and a major underutilized source of cost reduction and economic advantage.

The Electric Power Research Institute estimates that poor power quality costs American industry up to $188 billion per year in direct costs as well as lost productivity. That’s equivalent to the budgets of Ohio, Michigan, Indiana and Wisconsin put together.

In fact, there isn’t another cost reduction potential in industrial plants that comes close to this staggering total. And what’s more alarming is that industry studies have shown about 80% of this number, or $150 billion a year, is caused not by power quality from your electric utility, but by self-induced problems inside your facility, the vast majority of which can be diagnosed and corrected.

Power problems aren’t new, but they’ve almost always been either misunderstood, mismanaged or ignored. For most, unless you’re an electrical engineer, power terms and their associated problems such as harmonics, swells, power factor and more can be a mystery.

Many symptoms and signs of power quality problems occur sporadically, and often when companies least expect it. Major inefficiencies result from unplanned downtime caused by motors that suddenly die, machine controllers that mysteriously lose their programs or values, damaged drives, capacitors that short out and other major issues.

And, with more machinery being run by electrically sensitive equipment such as VFD drives and computerized controls, the problems are accelerating not diminishing. Because production is critical those failed components are often replaced instead of diagnosing and fixing the root cause, which can happen over and over. Part replacement costs soar. And, of course, the lost production time is never recovered.

Until now, diagnosing these costly events required a large group of highly-skilled electrical consultants, expensive specialized instrumentation, and capital appropriation through multiple approval levels.


The MachineSense Power Analyzer is the solution to this problem. This proven technology has been tested for two years with industrial professionals. The result is, the first affordable, easy-to-understand, 24/7 power analyzer for manufacturing professionals that are less skilled in electrical systems.

Click here to view the product

Call +1-410-968-6988 to speak with a sales representative with any questions that you may have.

It’s priced thousands less than the typical power instrumentation. Consider it an “industrial MRI” that diagnoses under the cover of your wiring, your electrical distribution grid and your powered machinery, so you can quickly and easily identify the internal power issues and get them repaired immediately.

With Power Analyzer, you’ll know what’s really happening inside your control panels, inside the wires in your walls and inside your drives. But unlike actual MRI reports, you don’t have to be an expert to read and interpret the results.

MachineSense electrical toroids are added directly to incoming power lines or machine power lines to continuously and automatically monitor current conditions. This 24/7 collection of data is sent through an internal datahub directly to your router and is analyzed by advanced cloud-based servers.

Our Crystalball software automatically translates complicated electrical graphs into intuitive, readable dashboards. Armed with this data, you can put together an action plan to tackle the biggest cost reduction opportunity and productivity enhancer in American industry today.

You’ll overcome poor power quality issues and achieve economic gains through reduced utility bills, lowered downtimes and improved productivity.

You’ll also avoid expensive part replacement as well.

You’ll realize a future with significantly reduced motor, drive, controller and capacitor issues.

You’ll be rewarded with dramatically reduced unplanned downtime, lower utility bills, improved productivity and profitability.

Your life just got a whole lot easier.

Let’s take a look at some common power problems and the solution to each.


Why do my electric motors fail?

AC induction motors fail due to following reasons:

1) Thermal stress on stator coil and rotor – thermal stress inside the motors can be caused by several conditions, most common among them:

  • Higher harmonics generated by DC drives or nearby Vector drives: Old DC drives for DC Motors and Vector drives for VFD and Servo are a major cause of high harmonic content in factory AC lines. A source closer to DC drives can have as high as 50% harmonics in the distribution unless any harmonic filters are used. Harmonics are unwanted part of the power spectrum and therefore dissipates as heat in the stator coil. 10-20% increase in current harmonics (current THD) can lead to a 30-70C increase of coil temperature and thus can create very high thermal stress which in turn can rapture the coil.
  • Unbalanced current phase condition: Unbalanced current condition (different amount of currents in different phases) creates a high amount of heat from an unbalanced amount of currents. Unbalanced currents are caused by uneven tapping of single phase current from different 3 phase current sources.
  • High ground noise: If electrical grounding is not proper, signal to noise ratio (SNR) of the current will be low. Due to the presence of high amount of current noise, coils can be heated easily, and thermal stress is generated.
  • High ambient temperature: Motor coils do produce resistive heat. This heat is dissipated via convection. If the ambient temperature is high, transport of the heat from Motor coil will be inefficient, and as a result, coil temperature will be higher.

2) Rusting and erosion: If motor is left in an area with high humidity and having gases that can lead to erosion of the coating of the Motor coil (which happens in oil and gas, mining, and many areas where air may get contained.

3) Mechanical stress on rotor from phase imbalance – rotor system can be subjected stress if currents in each phase are not equalized.

4) Surge in voltage: If a nearby transformer is suddenly brought to action, both current and voltage transient may take place which in turn may create additional tearing stress on the motor coil.

The Motor Analytic package from MachineSense can detect almost 80% causes and degradation of Motor rotors and stators.

The following images show common problems:

Voltage spike from inverter

Phase to phase imbalance and insulation breakdown

Turn to turn shorting among the Stator Coils

Defective magnetic wire insulation

Breakdown of ground insulation

 

Overheating damage to the Rotor cage

Aluminum cast bar – effect of thermal stress

Overheated aluminum fabricated Rotor bar

Filtering corrosion by Loose fitting in Bearing Cage

Metallic contamination in raceway

Images source.

Why do my capacitors fail?

Typically, most capacitors are broken into the following families of electrolytes:

  1. Aluminum electrolytic capacitors: Etched aluminum foil with aluminum oxide as dielectric
  2. Tantalum electrolytic capacitors: sintered pellet (“slug”) of high-purity tantalum powder (tantalum pentoxide as dielectric)
  3. Niobium electrolytic capacitors: high-purity niobium or niobium oxide powder (niobium pentoxide)

Wet aluminum capacitors are cheapest among all, and they are widely in use because of price range and availability. However, these capacitors are less resistant to sudden heat dissipation that can result from a current or voltage surge.

The electrolytic liquid inside capacitor cylinder expands with rising temperature at a much faster rate, and stress created on the capacitor wall by thermally expanding capacitance liquid can rapture the capacitance wall easily. The rise in temperature can happen when there is a voltage surge.

Energy stored in capacitance is proportional to the square of the voltage, and thus even the smallest voltage surge can trigger sudden swelling of the capacitor liquid due to the dissipation of energy inside it.

Now this kind of transient rise in Voltage, or voltage surge is not easily detectable unless there is a 24×7 type of voltage recording device that records voltage at a very high rate (such as 8000 samples per second).

Power Analyzer from MachineSense can do that by using its patent-pending FOG computation at Voltage sensor edge and offering the results in the Mobile app via IoT cloud.

What causes my PLC controls to dim?

Frequent PLC failure due to power surge:

PLC is at the heart of SCADA and control system in any manufacturing plants. If the factory power distribution is designed poorly or if the factory runs large VFDs or DC drives motors, PLCs can be burned out frequently or will be losing the memory quite often.

To understand this, we have to look at the power supply mechanism of PLC. Typically it is 24V DC or 220/110V AC to DC SMPS. In either of the cases, if AC input power is corrupt beyond a certain limit, electronics components of the PLC can be damaged easily. Permanent memory can be reset.

Typically, 24V or SMPS supply is robust against voltage and current surge. Also, all the power supply will have built-in protection. But if a large VFD is switched on in a close by area, two detrimental phenomena take place simultaneously, and their orchestration can damage PLC electronics.

First, during the start-up of large VFD motors, a large inrush current is generated which flow to the PLC power supply. However, the most damaging part is the high harmonic content of that currents. Vector drives generate 40-70% current harmonics. Although power supply will filter major part of the harmonics, higher order harmonics of Inrush current will sneak through and instantaneously heat up the PLC board.

This can also lead to voltage harmonic surge which in turn can damage PLC capacitors easily. RAM/EPROM of the PLC is highly susceptible to an unwanted surge in harmonics in current and voltage.

To deal with this kind of a nuisance, one needs to understand the surges which lead to frequent failure of PLC. Therefore, a high-quality recorder is needed which will capture voltage currents and its harmonics in each second for 24×7 operation. Also, the system should have built-in alarms so that the surges will be recorded and conveyed via SMS and email with a time stamp so that a correlation between surge and occurrence of the event of PLC destruction can be correlated.

MachineSense Power Analyzer provides such cost-effective IoT system which informs the users about powerful surges hitting the PLC and other controllers.


What causes bad power harmonics?

What causes poor harmonics and how do we address the problems caused by higher harmonics?

Current and voltage harmonics are the higher frequency components in the load where carrier frequencies are multiple of the fundamental frequency. Current harmonics are more common than voltage harmonics. However, each can produce the other.

In most of the inductive motors, harmonics part of the powers is dissipated as heat in the magnetic core of the Motor. Since the motor consumes a large part of the factory loads, higher harmonics contents in the power distribution lead to significant wastage of energy and thus loss of bottom line of the operation. Also, the heated motor core will degrade faster and will fail much earlier than recommended life cycle.

With the ubiquitous rise of mobile devices and the explosive growth of IoT, dc power supplies are seeing exponential growth. In commercial building and homes, rectifier diodes of the DC power supplies contribute as the highest source of harmonics.

Also, imbalanced currents of three-phase lines and vector drives of the motors also contribute to a high level of harmonics in the factories. Any kind of non-linear load will give rise to high harmonic contents. Since the use of vector drives and DC devices are at alarmingly high level, IEEE has issued a stringent standard for the utilities to comply with harmonics generation from the devices (Std. 519-1992).

In general power companies do a good job of maintaining IEEE 519 to keep the current harmonic contents less than 2-4% and feeding a balanced 3-phase supplies to building and factories. However inside the factories or buildings, when two-phase power is tapped from three phase, each phase will be drawing a different amount of current due to uneven tapping. Since two-phase drop depends on a number of active devices on that tapped line, it is always a dynamic situation, and irrespective of best effort 3-phase current supplies within a large commercial building or factory are typically imbalanced. The imbalanced load is the first source of harmonics.

Then the second largest source is DC power supplies in two-phase lines for a large commercial building. In the case of factories, however, old DC drives and vector drives contributes to as much as 25-70% THD (total harmonics distortion) which can kill the surrounding motors much faster.

To address frequent failures caused by harmonics, it is essential to keep a 24×7 current and voltage harmonics recorder inside different locations of a factory where sensitive and expensive machinery are installed. This is because harmonics percentage in the load varies with active two-port tapping and on-time of the DC and vector drives. Since the action of DC and vector drives depends on the random demand of load, harmonic percentage or THD fluctuates highly. Daytime THD is way higher than night time.

MachineSense Power Analyzer is one of the IoT based systems that capture and record higher harmonic contents of the Factory and Commercial building loads 24/7. If high THD is observed, MachineSense power analyzer alerts the customers automatically and will suggest possible remedial action based on the applications automatically.


What causes internal power quality conditions?

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