> Skip to Content

Tag Archive: motor drive

  1. What’s that Noise My Motor Bearing is Making?

    Comments Off on What’s that Noise My Motor Bearing is Making?

    In the course of our work, our team at Renown Electric Motors & Repair Inc. comes across a lot of motor drive and motor bearing issues.

    Noise coming from the motor drive or bearing is a particularly common complaint. Working with our partner NTN Corporation, a Japanese bearing manufacturer with global reach, we compiled a few common causes of noise and vibrations in bearings and drives — and how to fix them.

    What noise is my motor bearing making?

    Cylindrical Roller Bearing

    A motor bearing may make any number of noises, not all of which are indicative of a serious issue. Tinkling or rustling sounds, for example, are generally caused by dust or dirt and can be resolved with a decent cleaning. Others, however, can be more problematic.

    Buzz or Roar

    If your bearing is making a vibratory sound ranging from a light buzz to a considerable roar that increases in volume and pitch as speed changes, this is problematic.

    Spherical Roller Bearing

    This issue can be caused by any one of a number of factors, including resonation, a poorly shaped shaft, deformed bearing, brinelling, or vibrating parts. Note that in very large bearings, a minor buzzing is normal.

    Screech or Howl

    A screeching or howling sound, particularly on cylindrical roller bearings, that changes with speed is an indication of radial clearance that is too large.
    (Note that if the sound is metallic and fades temporarily after being greased, the lubrication you are using is of a poor quality.)


    A crunching sound, especially one that can be felt when the bearing is moved by hand, could be caused by a deformed bearing or bad dust contamination. More seriously, it could mean that balls, rollers, or raceway surfaces are being scored.


    A chatter that is audible not only at high speeds but at low ones as well can mean that the rollers on a full-roller bearing are bumping into each other.

    Find more causes of noise and vibration in NTN’s Motor Bearing Care & Maintenance Guide.


    Why is my motor vibrating?Motor Bearing Maintenance Guide

    What do each of these sounds have in common? They can be traced back to vibrations in the motor. The degree of the damage caused by these sounds’ sources depends on both the amplitude and frequency of the vibrations causing them.

    Slight motor vibration is normal. The presence of a variable frequency drive (VFD), while helpful for decreasing energy use, introduces electrical noise in the form of Common Mode Current. Common Mode Current can increase vibrations to dangerous levels that can cause audible noise issues and, more worryingly, badly damage your motor bearings.

    The Ultimate Solution

    CoolBLUE inductive absorbers, also called common mode chokes, are inductors that have been specially designed to reduce common mode current — they absorb the electrical noise, thus “choking” the current.

    Proper installation of CoolBLUE inductive absorbers and NaLA differential mode line absorbers, both manufactured by Renown partner MH&W International, can decrease VFD-caused Common Mode Current drastically, as much as 70% or more. By reducing this noise and the vibration it causes, you will maximize the longevity and reliability of your equipment while minimizing maintenance cost and unscheduled downtime.

    Learn more about Renown’s CoolBLUE Inductive Absorbers or see how they work in our motor bearing current case study.

  2. Motor Repair Projects: See How Renown’s Process Works

    Comments Off on Motor Repair Projects: See How Renown’s Process Works

    Renown Electric treats every motor project — big or small — with the same level of care to produce the best quality results for our customers.

    To illustrate how we handle motor repair projects smoothly from start to finish, we’ve compiled details from some of our past jobs into a new case studies page on our website. Here are a few highlights:

    Motor Repair


    In one recent case, a silicon rubber mill was experiencing brake issues as the result of an outdated control panel. The owner of the mill, which no longer met the required safety standards, approached Renown for motor drive maintenance assistance to help create a safer work environment. Renown collaborated with Mann Electric and a top motor and machine control support company, Benshaw Advanced Controls and Drives, to examine the controls.

    Collaboratively, we determined that the best solution would be to completely replace the control panel, while accommodating the old wound rotor motor. We reestablished workplace safety at the mill by providing a new motor control panel with advanced synchronous control capabilities, a soft start and emergency stop functionality to meet current workplace health and safety standards.

    Industrial Motors

    In an AC and DC motor case study, Renown conducted a motor bearing current test with our CoolBLUE inductive absorbers and NaLA noise line absorbers to find a solution to harmful voltage spikes, which had been causing fluting and lubrication breakdown. We found that these absorbers, also known as common mode chokes, reduced bearing damage by eliminating these high frequency currents and keeping voltage within safe limits.

    Two Male Technician Machinist Worker At Work Adjusting Elevator Mechanism Of Lift With Spanner

    Elevator Motors

    In another motor bearing current test — in this case, for elevator motor drives — Renown found that the common mode chokes reduced harmful electrical “noise” by up to 60% in DC motors and 65% in AC motors. This eliminated harmful currents to the armature and bearings and in the long run will reduce maintenance and prolong the life of the motor.

    Renown Can Help

    For more examples of recent projects and to learn how Renown can help you to prevent motor problems across a variety of applications, please visit our case studies page.

  3. How to Save Money on Your Electric Motor

    1 Comment

    Electric motors are the power sources regulating performance, speed, and torque in some of our most important commercial, residential, and industrial machines. But they’re also the single largest consumers of all electricity and, if not maintained properly, can cause costly downtime.

    Fortunately, there are several steps you can take to improve the life and performance of your electric motor, and cut costs significantly. These include:

    1. Soft Starts


    Without the use of a VFD, three-phase motors can start in three ways:

    • Hard start: A direct-on-line start with a very high starting current (6-10 times the rated motor current). This start spurs the motor to get to full speed instantaneously, which can cause belt slippage, heavy wear on bearings and gears, and possible damage to other components in the system;
    • Star delta start: Uses contactors and a timer to switch between star-position for starting (using 30% of starting current and 25% starting torque,) then moving to delta for full load;
    • Soft start: Gradually applies power to the motor and minimizes the initial jolt.

    Soft starts are the safest and most efficient of the three, protecting the facility from blown fuses, excessive voltage, and compromised electrical flow for other warehouse applications. Soft starters use thyristors, semiconductors, and silicon controlled rectifiers to control temperature shifts and electrical current flow as the motor starts, reducing the risk of electrical, technical, and mechanical failure.

    2. Motor Rewinding

    Rewinding a blown or burnt out motor can be a cost-effective and time-saving alternative to investing in a full replacement. Although some are weary of this practice, rewinding a motor, when done correctly, will allow for full restoration of the system’s operational efficiency.

    3. Motor Drive Maintenance


    Variable Frequency Motor Drives (VFD’s) convert electrical energy into mechanical energy, offering controls to regulate speed and torque. In fact, a properly functioning variable frequency drive can delivery up to 55% in energy cost savings.

    Unfortunately, many businesses put off motor drive maintenance until a system experiences a catastrophic failure. The resulting costs from a complete motor replacement, as well as lost profits from production downtime during installation, are often much more expensive than the price of routine maintenance and repair would have been. If you experience electric motor drive problems, take care of them early to avoid costly repair services.

    Want to Hear More?

    Renown Electric’s team of over 40 experts is committed to serving a diverse range of electric motor applications for a variety of industries around the world. Our latest eBook, 6 Ways to Save Money on Electric Motors, shares additional motor money-saving tips to help you cut costs.

    Simply visit our website to download your copy of this free eBook.

    Download Free eBook
    6 Ways to Save Money
    on Electric Motors

What kind of resource are you looking for?

Whether you're looking for preventative maintenance tips, equipment repair help, or technical guides on a particular product; our resource library has a variety of materials to answer commonly asked questions.


Most Downloaded Resources

Have any questions? We are here to help!