A new production line was installed about a year ago. A VFD-controlled 40-hp motor provides most of the motive thrust needed to get the materials from input chutes, through the process equipment, and out as parts to be sent to the finishing phase.
The problem is the motor periodically stops due to overload trip. The overloads have been checked multiple times; they are the correct size and type. The drive has been checked multiple times, also. It is set up correctly and passes all diagnostic tests.
A power analyzer shows minimal harmonic distortion, 98% power factor at the drive, no voltage imbalance, and minimal wave distortion. Everything is properly bonded.
How can you solve this problem?
Stop to consider why that motor would be periodically tripping on overload. There is only one reason: It periodically gets overloaded. If everything runs as intended, there's no overload. But things don't always run as intended. An unanticipated variance in load the motor must move can require more torque than the motor can produce. The motor will try to produce that torque anyhow, and as it draws more current to do that the overload protection kicks in.
One way to solve this is to use a bigger motor. But how big?
Another solution is to use a gearbox to multiply the torque. A VFD can't multiply torque; it can only control motor speed. By combining a gearbox with the existing VFD, you can get the torque.