by Howard Penrose, Ph.D., CMRP | Mar 28, 2020 | Electrical Reliability, Motors & Drives
The graph in Fig. 1 below is often quoted as showing the average failure rates in a population of electric motors throughout industry, and cited as the results of a 1983 Electric Power Research Institute (EPRI) study. This General Electric study of large power-plant...
by Howard Penrose, Ph.D., CMRP | Mar 14, 2020 | Electrical Reliability, Maintenance Management, Motors & Drives
In ball-bearing machines, the bearings are often cited as the primary cause of electric-motor failure. There are numerous lubrication and application issues that impact bearing life, as well as basically cause reduced life. While we will continue to return to the...
by Howard Penrose, Ph.D., CMRP | Mar 7, 2020 | Electrical Reliability, Maintenance Management, Motors & Drives
In this first part of a new series on electric motor systems, we’ll review the reliability of such systems. Let’s start by considering one the most-asked questions associated with the topic: “How long should the motor last?” While there are standards that...
by Howard Penrose, Ph.D., CMRP | Feb 21, 2020 | Electrical Reliability, Motors & Drives, Plant Operations
The purpose of high-resistance grounding (HRG) and low-resistance grounding (LRG) is to reduce fault currents and transient overvoltages in a high-energy system should a short to ground occur. This provides a number of benefits, including a reduction in arc-flash...
by Howard Penrose, Ph.D., CMRP | Jan 25, 2020 | Electrical Reliability, Motors & Drives, Safety Matters
One of the least understood, yet critical, components of power quality is the grounding system. While we cannot cover all variations of these systems, it’s important to note that the primary methods are grounded/bonded; resistance ground; and,...
by Howard Penrose, Ph.D., CMRP | Jan 12, 2020 | Electrical Reliability, Motors & Drives, Safety Matters
As noted in previous articles in this series on motor-driven equipment and electrical-system-reliability issues in today’s plants, the primary electrical concern is the supply to electric motors, i.e., the voltage. An electric motor is electrically designed around the...
by Howard Penrose, Ph.D., CMRP | Dec 20, 2019 | Electrical Reliability, Motors & Drives, Safety Matters
Voltage unbalance and its most severe form, single phasing, cause up to 14% of power-quality-related motor failures. It’s important to understand that maximum current unbalance is not defined in standards for electric motors in their operating environment,...
by Howard Penrose, Ph.D., CMRP | Nov 29, 2019 | Electrical Reliability, Motors & Drives, Safety Matters
Power quality involves a variety of impacts on the Voltage supply, the Current, and the grounding system While many standards and documents emphasize one part or another, the reality is all of these factors impact each other. Unfortunately, except for...
by Howard Penrose, Ph.D., CMRP | Nov 14, 2019 | Electrical Reliability, Motors & Drives, Safety Matters
Power harmonics are power-frequency notches in sinusoidal Voltage or Current that occur due to switching power supplies. In single-phase supplies, such as laptops, lighting, displays, and similar, you have 3rd harmonics. That means, if you have a 60Hz system, the 3rd...
by Howard Penrose, Ph.D., CMRP | Oct 22, 2019 | Electrical Reliability, Motors & Drives
One area that is extremely important to electrical reliability and operation of a plant is also one of the least understood. Unfortunately, some have taken advantage of that misunderstanding. This includes associating a reduction in current with reduced energy...
