In industry, every downtime is a loss, and one of the most common culprits is inverters. Their task is to control the operation of electric motors. They work in difficult conditions, often around the clock, supporting key production processes. However, all it takes is one mistake for the line to come to a standstill and the loss counter to start ticking.
In this article, we've compiled five common faults that occur in industrial inverters. You'll learn their causes and potential consequences.
#1 Inverter overheating
Inverter overheating is one of the most common problems faced by maintenance departments. The device operates under heavy load and when the temperature of its components exceeds acceptable limits, it becomes less stable or enters emergency mode, which can cause the engine to stall.
The cause may be insufficient heat dissipation. Blocked or dirty heat sinks, inoperative fans or poor air circulation in the control cabinet cause internal temperatures to rise. The inverter's location also contributes to overheating. If it's installed in a location with high ambient temperatures or close to heat sources, the risk increases severalfold.
The cooling system's performance is also affected by operating conditions. Frequent operation at maximum performance limits, excessive engine load, or prolonged braking cycles can cause excessive heating of power components. Over time, this leads to insulation degradation and a shortening of the capacitors' lifespan or damage to transistors.
#2 Inverter input/output short circuit
A short circuit at the inverter input or output is one of the most critical faults that can occur during drive operation. It causes the device to shut down immediately and often requires thorough diagnostics, as it may have its source both on the inverter side and in the external installation.
An input short circuit can occur due to damaged insulation in the power supply wires or grid overload, which causes current to flow outside the intended path. Another factor can be faulty internal components of the inverter, such as bridge rectifiers or IGBT modules, which lose their properties due to overheating or degradation, causing a short circuit.
In turn, a short circuit at the inverter output is often linked to problems on the motor side. Damaged windings, ground faults, moisture inside the stator, or mechanical damage to the motor power cables can all lead to a sudden current spike.
In industrial environments, additional risks include vibration and shock, which can loosen connections over time and increase susceptibility to short circuits.
#3 Inverter does not start the engine
A situation in which the inverter remains in standby mode but the motor does not start is a problem that can have many sources. It often results from interference in the control signal path or incorrect control input assignments. Loose connections, damaged signal cables, or errors in the configuration of operating parameters can contribute to this. Even a slight discrepancy between inverter settings and the drive requirements can effectively prevent the engine from starting.
Another common cause is a power circuit break. Damage to the motor windings, blown fuses, improper wiring to terminals T1, T2, and T3, or wear and tear from years of use can result in the drive failing to operate despite a start signal being applied.
#4 OverCurrent error in inverters
The OverCurrent error is a common alarm in inverters. It indicates that the current in the motor circuit has exceeded the permissible value programmed in the device. This can occur both during start-up and during steady-state operation of the drive.
In production plant conditions, this phenomenon may be a consequence of a sudden increase in load or a mechanical blockage in the driven system, which causes a sudden increase in current consumption.
The causes may also include incorrect configuration of the inverter parameters regarding the power and characteristics of the motor. Too short an acceleration time or sudden speed changes can cause a momentary overload, which activates overcurrent protection. In some installations, worn mechanical components can also pose an additional problem, increasing the resistive torque and therefore the current demand.
The effects of an OverCurrent error are not limited to simply shutting down the drive. Each such event carries the risk of excessive heating of the motor windings and power components in the inverter, which in the long run shortens their service life.
#5 Inverter takes a long time to start or doesn't start at all
Delayed inverter start-up or a complete lack of response to a start command is a problem that can paralyze entire production lines in manufacturing plants. The causes of this can be both electrical and electronic. One of the most common sources of the problem is the degradation of capacitors in the inverter's power supply circuit – components that lose their properties over time, causing slower charging or unstable operation during startup.
Another factor is damage to the power or control circuits, which can result from previous overloads, voltage spikes, or unfavorable environmental conditions such as high humidity or excessive dust. In some cases, the problem occurs after the device has been idle for a long period. In this case, the semiconductor components and contacts may require more time to stabilize their operating parameters.
Inverters can fail in a variety of ways, and each failure can have many possible causes and effects. Therefore, if you experience any problems, it's best to contact your local dealer right away.with service, instead of risking repairing it yourself without experience.
