What you are seeing
The drive runs for a while, then throws a code and stops the motor. Sometimes it trips the instant you hit start, sometimes only under load, sometimes hours into a shift with no obvious trigger. You reset it, it runs again, and a little later you are back where you started. On a conveyor or a pump that means the line stops with it, and the reset dance gets old fast.
The most common fault families you will see on the display are overcurrent, overvoltage, overheat, and ground fault. Each one points in a different direction, so the code on the screen is your first and best clue. Write it down exactly, along with whether it trips at start, at speed, or only under load.
Read the fault code first: OC, OV and GF
Before you reset anything, look at the display. Three of the codes you are most likely to see on a drive that keeps tripping are OC for overcurrent, OV for overvoltage, and GF for ground fault. Each one points somewhere different, so the code tells you where to start looking.
Every manufacturer labels faults a little differently. One drive shows OC, another shows a letter and a number, and some split overcurrent into separate codes for speeding up, running, and slowing down. The ideas below apply to all of them, but the manual for your drive is the final word on what its code means.
Safety first. A drive stores energy in its DC bus capacitors, and that charge can stay dangerous for minutes after the power is switched off. Most drives carry a label stating how long to wait. Opening a drive, measuring voltage, testing wiring, or changing connections is work for a qualified person, with the machine locked out and verified dead. Never jumper out, disable, or turn up a protection setting to keep a drive running. Before you reset any fault, make sure everyone is clear of the machine, because some drives start again on their own after a reset if the run command is still on.
OC overcurrent at startup: why a conveyor trips the moment it starts
What it usually means. The drive saw its output current jump past a safe limit, so it shut the output off almost instantly to protect itself. That is different from an overload fault, often shown as OL, which trips after the motor has worked too hard for too long. An OC trip is fast and sharp, which is why it so often shows up right at start.
Common causes
- The load will not turn freely: product jammed on the conveyor, a seized bearing or roller, a chain that is too tight, or a gearbox problem.
- A motor brake that is not releasing, so the motor is trying to drive through it.
- An acceleration ramp that is too short for how heavy the load is.
- Motor data that was never entered, or settings that do not match the motor, such as too much torque boost or a skipped motor auto tune.
- A short or a ground in the motor winding, or in the cable between the drive and the motor.
- A contactor or disconnect between the drive and the motor that opens or closes while the drive is running.
- The drive starting into a motor that is still coasting from the last stop.
- Less often, a drive that is too small for the job, or a drive that has actually failed.
What a qualified person checks first
- When in the start it trips. A trip before the shaft moves at all points at a short, a ground, or a locked load. A trip a second or two into speeding up points at the ramp, the load, or the settings.
- With the conveyor locked out, whether the belt, rollers, and drivetrain turn freely, and whether any brake actually releases.
- The drive fault history, and the motor settings compared against the motor nameplate: current, voltage, frequency, speed, and the acceleration time.
- With the motor leads disconnected from the drive, an insulation resistance test of the cable and the motor, plus a check that the windings are balanced. That test is never run with the drive still connected, because the test voltage can damage the drive.
- Once the load is confirmed free and the motor tests good, whether a longer acceleration ramp stops the trip.
Clearing it without replacing the drive. The code itself clears with a normal reset once the cause is fixed. An OC trip at startup often has nothing to do with a bad drive, and a new drive installed before the load, the motor, and the settings are checked can throw the exact same code.
When to stop and call a professional. Stop resetting it if it trips again right after a reset, if it trips before the motor turns at all, or if there is any burning smell, heat, or discoloration at the motor. Those are the cases where one more start can damage a motor winding or the drive.
OV overvoltage during deceleration: why the drive trips when the motor slows down
What it usually means. When a drive slows a motor down, a heavy or fast moving load keeps pushing the motor, and for that moment the motor acts like a generator. That energy flows back into the drive and raises the voltage on its DC bus. If the voltage climbs past the drive limit, it trips on OV to protect its capacitors and power parts.
Common causes
- A deceleration ramp that is too short for the weight and speed of the load. Fans, blowers, flywheels, centrifuges, and loaded conveyors are common examples.
- A load that pushes the motor, such as a conveyor running downhill or a hoist lowering. That kind of load can trip OV even at steady speed.
- A braking resistor that is missing, too small, disconnected, or burned out, or a braking function that was never turned on in the drive settings.
- Supply voltage that is high or spiking. If OV shows up while the motor is idle or running at steady speed, look at the supply, not the ramp.
How a qualified person tunes it
- Confirm the trip really happens during the stop, not at idle or at steady speed.
- Lengthen the deceleration time in steps, and test each step with a normal stop under a normal load. Keep the shortest time that stops the trip, with some margin.
- Check whether the drive has an overvoltage control function, which goes by different names, that stretches the ramp automatically when bus voltage climbs. It works, but it makes the stop longer and less predictable.
- If the process needs a faster stop than the drive can manage on its own, or the load pushes the motor, the fix is braking hardware sized from the drive maker data: a braking resistor, or where a lot of energy has to be absorbed, a regenerative unit.
- Where the process allows it and it is safe, a coast to stop can remove the problem entirely.
One thing not to skip. A longer ramp means a longer stopping distance. If how quickly the machine stops matters for safety, including how its emergency stop works, a qualified person has to confirm the change is still safe before the machine goes back into service.
When to stop and call a professional. Call if OV happens while the motor is not slowing down, if a braking resistor looks discolored or smells hot, if the ramp would have to be so long it slows production, or if the load pushes the motor. Braking resistors can run hot enough to burn, so do not touch one.
GF ground fault after the motor runs a while: is it the motor or the drive?
What it usually means. The drive measured current leaking from its output to ground, meaning some current is taking a path other than out to the motor and back. Drive ground fault detection is there to protect the equipment. It is not designed to protect a person from shock.
Motor, cable, or drive?
The fault is usually in the motor or in the cable between the drive and the motor, not in the drive. A trip that only comes after the motor has been running tells you something changes as it runs:
- Winding insulation that breaks down as the motor warms up.
- Vibration moving a damaged wire against metal.
- Moisture in the motor terminal box, a junction box, or the conduit.
- A cable on or near a moving part that is rubbing through.
Long motor cables, unshielded runs, or a high carrier frequency setting can also let enough leakage current flow to trip GF with no damaged wire at all. The drive itself can be the cause, through a failed output or current sensing part, but that is normally proven by testing the motor and the cable first and finding them good.
What a qualified person checks first
- Lock out, verify the machine is dead, and wait out the DC bus discharge time on the drive label before touching anything.
- Disconnect the motor leads at the drive, then insulation test the cable and the motor separately. Never test through the drive.
- Because this fault waits until the motor is warm, test as soon as practical after a run, once it is locked out. Insulation that passes cold can fail warm.
- Open the motor terminal box and any junction boxes along the run, and look for water, corrosion, burned insulation, or chafed wire. In humid South Florida plants and wash down areas, this is worth checking early.
- Check the ground and cable shield connections at both ends, and compare the cable length and carrier frequency setting against the drive manual.
- Only if the motor and the cable both test good, test the drive using the manufacturer procedure.
When to stop and call a professional. Treat GF as a real electrical fault from the first trip, and do not keep resetting it. Current leaking to ground can put a shock hazard on the machine frame and can burn up a winding or a cable. This is the code to stop and call on.
Not sure what your code is telling you? Call or text a qualified technician before you reset it again. Ogun Factory Automation: 954 798 5143.
Have the exact fault code ready, when it trips (at start, while running, or while stopping), and a photo of the drive display and the motor nameplate.
Common causes, and where each one points
Usually a mechanical or motor problem, not the drive. A jammed conveyor, a seized bearing, a load the drive is trying to accelerate too fast, or a shorted or grounded motor winding will all pull current the instant it tries to spin. If it trips before the motor even turns, look at the mechanical load and the motor, not the parameters.
The motor and drive are working harder than they are sized or tuned for. A worn mechanical drivetrain, a clogged pump, an undersized drive, or an acceleration ramp set too aggressive will all show up as an overload once the work starts. Overload trips that get more frequent over weeks usually mean something is wearing.
A fast stop on a high inertia load feeds energy back into the drive, and with nowhere for it to go the bus voltage climbs until the drive trips to protect itself. That points to the deceleration ramp being too short for the load, or a missing or failed braking resistor.
The drive is cooking. Blocked cooling fins, a dead cooling fan, a clogged filter, an enclosure with no ventilation, or a South Florida panel sitting in the heat with the door shut will all push a drive over its thermal limit. This one is often the cheapest to fix and the easiest to miss.
A drive that was swapped in but never programmed for your specific motor and load will trip on defaults that do not match your equipment. Motor nameplate data, current limits, and acceleration settings all have to be set for the machine the drive is actually running.
These point at the wiring between the drive and the motor, or at the motor itself. A nicked conductor, moisture in a junction box, or a motor winding breaking down to ground will all show here. This is where you stop and treat it as a real electrical fault.
What you can check safely
Safety first. A running drive holds a dangerous charge on its DC bus even after power is removed. Do not open a drive or land wires unless you are qualified and it is fully de-energized and verified. The items below are the safe, useful things an operator or maintenance lead can check first.
- 1 Read the exact fault code off the display and note whether it trips at start, at speed, or on stop. That one detail cuts the problem in half.
- 2 Turn the driven equipment by hand if it is safe to do so. If a conveyor, pump, or fan is stiff, dragging, or seized, the drive is doing its job by tripping.
- 3 Feel and look at the drive and enclosure. Is the cooling fan spinning, are the fins caked with dust, is the panel sitting in direct heat with the door closed?
- 4 Check whether the trips started after any change: a new drive, a motor swap, a mechanical repair, a production speed increase, or hot weather.
- 5 Look for the obvious at the motor: burning smell, discoloration, moisture, or a nameplate that does not match what the drive is set to.
- 6 Note the pattern. Every start, only under full load, only on a fast stop, or random. Bring that pattern when you call, it saves diagnostic time.
When to call a pro
If the drive trips on ground fault, on an output phase fault, or right at start with a burning smell or discoloration at the motor, stop resetting it. Repeated resets into a real electrical fault can turn a repairable motor or a good drive into a replacement. That is the point to bring someone in to test the motor windings, the drive output, and the wiring properly.
You also want help when the trips are intermittent and you cannot tie them to a pattern, when the drive was replaced but never set up for your motor, or when the fault is overvoltage on a hard stopping load and you are not sure whether you need a braking resistor or just a longer ramp. Those are diagnosis, not parts swaps, and guessing gets expensive.
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