April 21, 2017

Increased efficiency for uninterruptable power supply


CP Automation now distributes and fits the REVCON boost converter module RSU as part of its range. This unit enables highly efficient uninterruptable power supply (UPS) of variable frequency drives (VFD). This compact power unit has huge cost saving implications for anyone that uses power loss ride through in their processes.

UPS systems provide an electrical supply that is converted from batteries when the mains supply is lost in situations such as brown outs, unstable supplies or emergency lift evacuations. The REVCON boost converter module RSU is set to change the way factories maintain their power supply.

"Traditional UPS systems lead the power to the VFD through the complete UPS application, even when power supplies are operating normally," said John Mitchell, global business development manager at CP Automation. "This results in unnecessary power losses due to rectification and invertation of the voltage.

"By adding a REVCON boost converter to the system, the UPS remains inactive when power supplies are working normally. This means the VFD is supplied directly by the mains, rather than having the middle-man UPS system causing unnecessary power losses."

When the mains power supply is down, the REVCON boost converter is activated and sets the voltage value from the batteries to the required level of the VFD. This maintains the power supply in the DC bus to the VFD, without any interruption.

This simple principle enables a highly efficient, yet inexpensive option for uninterruptable power supply to VFD drives. While conventional UPS systems have an efficiency of 90 to 95 per cent, adding a REVCON boost converter means the UPS setup will have efficiency greater than 99.5 per cent. This has huge cost saving implications for a range of industries that use power loss ride through in their processes.

CP Automation is available to supply and install the REVCON boost converter module RSU. For more information about CP Automation's catalogue of REVCON products, go to www.cpaltd.net.

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April 03, 2017

Common causes of electric motor failure


Modern electric motors may be more efficient and reliable than their ancestors, but they can still fail sometimes. Here, Martin McGuffie, service manager of Euroserv, sister company of CP Automation, explains the three common causes of electric motor failure and how maintenance staff can reduce the impact equipment failure can have on business.

How long do electric motors actually last before they break down? The answer is often disputed, with some manufacturers stating 30,000 hours and others suggesting they can power through for up to 40,000 hours. However, most manufacturers are in agreement that electric motors last much longer when maintained properly.

Understanding the state of an electric motor’s health requires a range of tools and techniques, as well as thorough record keeping and regular maintenance. This allows the engineer to identify trends or weak points more easily.


Weakened insulation

Nearly half of electrical failures in motors begin with weakening of the insulation around individual wires in the motor coils. This is often caused by thermal stress, contamination and movement of the winding due to the magnetic forces during start-up and shut-down of the motor.

Overheating can also cause the winding insulation to deteriorate quickly — for every ten centigrade rise in temperature, the insulation life is cut in half. Overheating can occur when the power quality is poor or when an electric motor is forced to operate in a high-temperature environment.

Contamination

Contamination is another one of the leading causes of motor failure. Contaminants include airborne dust, dirt or any abrasive substance that finds its way into the motor. When they come into contact with the motor, foreign bodies can cause denting of the bearing raceways and balls resulting in high vibration and wear.

Luckily, preventing contamination is fairly easy. Main sources of contamination include dirty tools, work areas and hands. Motors can also be contaminated by foreign matter in lubricants and cleaning solutions.

Engineers should keep work areas, tools and fixtures clean to help reduce contamination failures. Also, when laying out the space, companies should try to keep motor assemblies and operation areas away from grinding machines to reduce the amount of foreign bodies that might contaminate the motors.

Lack of maintenance

A well-planned preventative maintenance programme is the key to dependable, long-life operation of motors and generators. It also helps reduce unscheduled production stoppages or long repair shutdowns.

The first step towards preventative maintenance is understanding how often tests need to be carried out on the motor. This varies, depending on the age, condition and quality of the machine, as well as the environment it operates in.

Static tests are an easy method of identifying weaknesses within the motor winding. The tests focus on winding and insulation resistance, as well as turn-to-turn and phase-to-phase insulation condition. With the right equipment, these tests can be performed without taking the motor off site, thus minimising downtime.

Motor testing and analysis equipment, such as Euroserv’s SKF Static Motor Analyzer Baker DX, can survey all insulation and windings in AC and DC motors, coils and generators. During a site visit, Euroserv attends with the all-in-one tester, providing customers’ maintenance staff an analysis of the condition of the impedance, capacitance, phase angle, resistance, insulation and step voltage.

Motor failure can cause downtime, meaning companies can lose thousands of pounds every minute when operations are stopped. Instead of exposing themselves to downtime, customers should request regular motor testing and analysis, ideally every six months, to ensure their electric motors are healthy, efficient and reliable.

To find out more information about the SKF Static Motor Analyzer Baker DX, get in touch with Euroserv here.