Arc Systems

Power supply irregularities’ can cause damage to your motor causing premature faiulres.  Harmonics will cause overheating and decreased efficiency. Voltage spikes tend to cause turn-to-turn stator winding failures. A single phased winding failure is the result of an open in one of the motor phases that supply power to the motor. The open is usually caused by a bad fuse, bad connection, an open contactor or a broken power line.

Environmental conditions such as humidity can cause a problem when the motor is de-energized long enough to drop near the dew point temperature because moisture weakens the dielectric strength of electrical varnish and other insulating materials.  This moisture also contributes to corrosion of bearings and other mechanical components

Contamination is never good for electrical components. Contamination can destroy motors in three ways: Some airborne particulates are very abrasive. Motor coils flex when in use and contamination with abrasive particles eats away the wire enamel. Some substances, such as salt or coal dust are electrically conductive. Heavy accumulation of contaminants typically obstructs cooling passages.

Improper Lubrication will cause premature bearing damage. If careful control is not practiced, grease can introduce contaminants into bearings. Mixing greases with different bases may also cause grease components to separate and run out causing dry bearings.

A variety of mechanical loads can also lead to early motor failure. Dynamic imbalance and/or misaligned coupling to next assembly can cause excessive loads. These extreme loads can cause bearing failure and stator failures due to higher currents trying to overcome these loads.

 

An overload occurs when the motor is made to draw more current than it was designed to accommodate, causing it to overheat. The high temperatures create additional stress on the motor’s parts, shortening motor life. Overloads can be caused by malfunctioning equipment, a broken gear or frozen bearings.

To summarize, the most common reasons for motor failure are:

 1- voltage unbalance causing overheating and insulation breakdown
2- voltage surges causing winding failures
3- bearing failure causing excessive heating
4- overload of the motor leading to excessive heat and failure
5- restrictive ventilation causes motors to operate at higher temperatures
6- moisture causing stator shorts

7- vibration causing mechanical stresses

8- bad design

ARC Systems, Inc. has been designing and manufacturing motors for over 40 year. We can offer to protect you from the environments by using:

• Class H Insulation System
• Vacuum Pressure Impregnation
• High Temperature Structural Adhesives
• High Quality Bearing
• Epoxy Paints
• Water Resistant Design
• Encapsulated Windings

 

We can provide equipment built to existing drawings or by working concurrently with your engineers, we can provide custom design products to your specification. 

Let us be your contract manufacturer for aerospace actuators, assemblies, and motion control components. 

By working with a motor design engineer you can ensure to get the right motor for your application.  This is why it is important to seek out a motor manufacturer before finalizing any design. ARC Systems, Inc. has been producing motors and motion control components for over 40 years. We can assist you in choosing the right motor for your application.

Have you ever had a motor that failed prematurely?

Did you ever ask yourself ‘why do motors fail?’ or ‘what can I do to prevent them from failing?’

The more we understand why motors fail, the better we become at addressing the problems.

Electric motors are the most common machine used in all facets of the world.  They are an essential part of our daily life as many systems, applications, and services depend on them. When they fail, it typically means extensive equipment repair or replacement.  This high cost of repair is often minor compared to the impact of unscheduled system downtime.

First and foremost, a poor motor design will cause premature motor failures. When the wrong motor is chosen failures are inevitable. A wrong choice may simply be a motor that is too small or have the wrong starting torque characteristics for the required load. The less torque the motor has, the slower the acceleration time resulting in more heating. If the slot fill of the stator assembly is low, the motor will see higher losses. A tight slot fill ensures maximum copper volume for reducing resistance losses and also allows for proper heat conduction to the motor housing. A high slot fill also prevents damaging vibrations between turns and stator stack.

 

More efficient motors run cooler. A high-quality designed motor is one with high efficiencies, high torques, and a large thermal margin. Tooth density, lamination design, rotor design, and air gap width are all factors which can increase efficiency. A well designed motor will ensure the end turns are laced and the stator windings are varnished.  This will guarantee the windings are solid. Lack of proper support of the winding can cause vibration between turns, phases and ground at start up.

Most motor failures are caused by a combination of various stresses that act upon the stator insulation, bearings and rotor shaft assembly. If these stresses are kept within the design capabilities of the system, premature failure shouldn’t occur. However, if any combination of the stresses exceeds the design capacity, the life of the system could be significantly reduced and catastrophic failure may possibly occur.

Motor failures can be caused by heat, supply irregularity, environmental conditions, contamination, improper lubrication, and abnormal mechanical loads.

Temperatures higher than the design rating eventually take their toll in numerous ways. The insulation deteriorates at a rate that may double for every 10 ºC. Motors using class H insulation in its construction will have a longer thermal life then class B or F. Excessive temperatures will also causes separation of greases and breakdowns of oils causing untimely bearing failure.

There are several reasons for motors to overheat. If the motor is overloaded, the winding temperature will rise. This is also true for low or unbalanced voltages, inadequate ventilation and too frequent start/stalls. 

Stator insulation failure is typically due to vibration, voltage surge, abrasives, and contamination by hostile environments.  Deterioration of insulation can be a result from unequal voltage between phases. Unequal voltages usually are caused by unbalanced loads on the power source, a poor connection at the motor terminal, or a high resistance contact. A one-percent voltage unbalance can result in a six to ten percent current unbalance which can cause insulation breakdown and failure. Deterioration of the insulation system is also caused by very high currents in the stator winding due to a locked rotor condition. It may also occur as a result of excessive starts/stops and reversals.

By working with a motor design engineer you can ensure to get the right motor for your application.  This is why it is important to seek out a motor manufacturer before finalizing any design. ARC Systems, Inc. has been producing motors and motion control components for over 40 years. We can assist you in choosing the right motor for your application.

In part two of this blog, we will talk about how power supply irregularities, environmental conditions, contamination, and improper lubrication are also causes for motor failures.