How To Diagnose And Fix VFD Overcurrent Trips
VFDs play an important role in a variety of industrial environments. The most basic function of a VFD is to control the speed and torque of the electric motors utilized by each industry, making them an integral part of energy efficiency and precise control of processes. Unfortunately, the most common problem experienced by end-users is the occurrence of overcurrent trips while using a VFD. In order to minimize any possible downtime and damage to the equipment, it is crucial to identify symptoms, establish the cause of the trip, and determine the most effective method to repair it. This article will explore diagnosing and troubleshooting of VFD overcurrent trips.
What is a VFD overcurrent trip?
A shutdown will occur automatically when a VFD goes into a trip condition because of an over-current condition, indicating that the current of the drive has exceeded its defined limit. The protection system has been established to protect the VFD and the associated motor from damage, but if the fault is happening frequently, there may be an underlying issue causing the problem to repeat itself. Finding the solution is usually related to determining whether there is a problem with the motor, the VFD itself, or the environment in which the system operates.
Key causes behind VFD overcurrent trips
1.Motor overload conditions
The most frequent cause of an overcurrent fault is an overloaded or high impedance motor due to a large applied load. An overloaded motor may have been sized incorrectly for the total amount of mechanical energy applied to it or the applied load has increased beyond its capacity due to problems with its mechanical parts causing the rotor to rotate slower than its operational speed. Increased mechanical resistance due to excessive friction, worn bearings or misaligned shaft connections will also result in the added electrical load causing the motor to produce excessive current beyond its rated values.
2.Short circuits or ground faults
Electrical issues including ground faults and short circuits, whether on a motor or in a motor’s cable, can result in overcurrent trips. Excessive currents may be caused by direct wire-to-wire connections from a motor’s damaged insulation or winding fault resulting in VFD protections being activated.
3.Improper VFD parameter settings
The failure of the VFD to meet the motor’s settings can cause the system to run inefficiently or, in some cases, cause it to shut down completely. For instance, an incorrect acceleration or deceleration time can lead to excessive current surges. Likewise, a low current limit could cause the unit to trip unnecessarily.
4.Abrupt load changes
If sudden load changes happen to the load from any connected devices, such as compressors, pumps and conveyors that are all driven by a VFD then the VFD could see this as an overcurrent problem and trip out of protection.
5.Environmental factors
Lack of proper ventilation causes motor and VFD to create dirt or debris. This debris can lead to overcurrent faults. VFDs work best when they are clean, in a temperature-controlled environment.
