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Typical Variable Speed Drive Faults and How to Troubleshoot Them: Ground Faults

Variable speed drives are equipped with some degree of protection against ground faults generated on the load (output) side of the drive. This is intended to protect the drive in the event of a fault in the motor leads or the motor itself. Here we examine the causes and effects of these faults on drives, and ways of resolving them. 

Variable speed drive (VSD) ground faults are intended to trip the drive before its output power section is damaged. They are typically displayed as “GF” or an analogous code on the drive’s HMI. These faults may also be termed “earth leakage” in some drive manuals. When they occur, they usually indicate problems with the connected cabling or motor, and need to be addressed promptly. Let’s explore some basic causes and corrective measures.

The most common causes of drive ground faults are motor cables shorted to ground, or motor windings shorted to ground. As we have referenced in past articles, the characteristics of the synthesized AC output voltage and current from a pulse width modulated (PWM) variable frequency drive (VFD) can place additional stresses on cables, motor leads and windings. Particularly […]

By |2020-05-07T10:55:24-05:00November 25th, 2019|Uncategorized|0 Comments

Typical Variable Speed Drive Faults and How to Troubleshoot Them: Drive Overload

Drive Overload faults can manifest themselves in response to rapidly changing load conditions or drive transistor over-temperature, among other causes. Below we discuss these faults, their causes and possible resolutions.

Variable speed drive (VSD) overload faults are intended to trip the drive before significant damage to internal components occurs. Various manufacturers have different means of monitoring drive loading and issuing faults when anomalies occur, depending on programming. Let’s examine what can trigger these faults, and how they can be corrected.

Overload faults can be generated in response to loading which exceeds the rated capacity of the VSD, or to user-programmed settings customized for the application. The first instance simply means that the rated current-carrying capacity of the VSD is being exceeded by a percentage and/or for a time greater than the specifications indicate, which can result in drive overheating and, ultimately, damage to internal components. Most drives are manufactured with a specific overload rating, in percent of rated output current and for a specific amount of time. For example, a VSD rated for what is termed “normal duty” might have an overload rating of 120% of rated output current for 60 […]

By |2020-05-07T10:55:24-05:00November 13th, 2019|Uncategorized|0 Comments

Typical Variable Speed Drive Faults and How to Troubleshoot Them: Output Phase Loss

Today we examine the Output Phase Loss fault, as we continue with common Variable Speed Drive faults, their causes, and some ways to resolve them.

As noted in our previous articles, Variable Speed Drives (VSDs, a.k.a. Adjustable Speed Drives (ASDs) or, for AC motor control, Variable Frequency Drives (VFDs)) are equipped with a number of monitoring and control features, including extensive monitoring of power output to the load. One critical function monitored is the health of each phase of the VSD’s output; when a fault occurs there, it is termed an Output Phase Loss. Let’s examine what triggers this fault, and how to address it. Output Phase Loss is typically indicated on the drive’s HMI by some alpha or numeric designation, which varies depending on the drive. For purposes of this discussion, we’ll note it is indicated by “LF” (in the case of the Yaskawa GA800) (see Fig. 1) or a numerical code (on the ABB ACS880, “3381”).  This condition can result from a number of problems related to the output cabling, the connected motor, or the VSD’s output (inverter) section. One of the most common causes is a break in the connection to […]

By |2020-05-07T10:55:24-05:00October 28th, 2019|Uncategorized|0 Comments

Typical Variable Speed Drive Faults and How to Troubleshoot Them: Over-Voltage

Today we look at overvoltage faults, as we continue with some of the more common faults experienced by variable speed drives, their causes, and some ways to resolve them. Variable Speed Drives (VSDs, a.k.a. Adjustable Speed Drives (ASDs) or, for AC motor control, Variable Frequency Drives (VFDs)) are equipped with a number of monitoring and control features intended to protect the drive and its connected equipment from damage. Errors, Warnings, and Faults are logged in response to abnormal operating conditions and displayed on the drive’s HMI and/or sent to monitoring software in connected PCs or automation control systems. The drive’s response to the abnormal condition depends on the condition’s severity, and the potential it has to inflict damage. The faults we are discussing typically cause drive shutdown, and require that the fault be corrected and the drive reset or rebooted before it can operate normally.

By |2020-05-07T10:55:25-05:00October 8th, 2019|Uncategorized|0 Comments
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