Genset and VFD overvoltage

[ptonsparky]

The last day of spud harvest before they put the equipment away for the year a customer had us come look at the Sorters. These are manufactured for the purpose and we normally do not have to work on them They work. The drives had been shutting down for no apparent reason to the operators throughout a good share of harvest. Naturally everything worked while my tech was there. He brought the manual back so we could find the stored fault codes at a later date. All the VFDs indicate an overvoltage at some point in time.

The manager knows they had rented a smaller genset than usual and it grunted to take up the load of the larger across the line start motors.

I'm thinking problem found. Yes/No?

 

[ATSman]

The last day of spud harvest before they put the equipment away for the year a customer had us come look at the Sorters. These are manufactured for the purpose and we normally do not have to work on them They work. The drives had been shutting down for no apparent reason to the operators throughout a good share of harvest. Naturally everything worked while my tech was there. He brought the manual back so we could find the stored fault codes at a later date. All the VFDs indicate an overvoltage at some point in time.

The manager knows they had rented a smaller genset than usual and it grunted to take up the load of the larger across the line start motors.

I'm thinking problem found. Yes/No?

Well, if the load was greater than the KW rating of the genset then yes it could have adverse affects on VFD operation.
But I am a little puzzled by what you stated: "All the VFDs indicated an OV......."
Then state ".... it grunted to take up the load of the larger across the line start motors."
So are the larger motors not on VFDs ?

 

[ptonsparky]

Well, if the load was greater than the KW rating of the genset then yes it could have adverse affects on VFD operation.
But I am a little puzzled by what you stated: "All the VFDs indicated an OV......."
Then state ".... it grunted to take up the load of the larger across the line start motors."
So are the larger motors not on VFDs ?

The VFDs that fault are on the Sorter. The larger associated equipment has a 20 HP. Full voltage across the line start.

 

[ATSman]

Ok, then it sounds like the 20HP motor is causing the genset to temp become overloaded. Then to compensate for this condition the voltage regulator/ governor overshoot causing the OV measured by the VFDs.
Solution: bigger genset.

 

[GoldDigger]

Ok, then it sounds like the 20HP motor is causing the genset to temp become overloaded. Then to compensate for this condition the voltage regulator/ governor overshoot causing the OV measured by the VFDs.
Solution: bigger genset.

Alternate solution: some sort of soft starter for the 20HP motor.
It is not good for the generator to be lugged down regularly by a high motor starting load.

 

[Jraef]

Alternate solution: some sort of soft starter for the 20HP motor.
It is not good for the generator to be lugged down regularly by a high motor starting load.

Yep, and cheaper than a new generator...

 

[LRB]

They rented the Gen Set. They own the starters. I would opt to rent a larger gen set, have overall more stable operation.

 

[GoldDigger]

They rented the Gen Set. They own the starters. I would opt to rent a larger gen set, have overall more stable operation.

Yup, fix the problem before it occurs again next year.

 

[LRB]

They rented the Gen Set. They own the starters. I would opt to rent a larger gen set, have overall more stable operation.

 

[ptonsparky]

They rented the Gen Set. They own the starters. I would opt to rent a larger gen set, have overall more stable operation.

The only part that had changed over the last several years was the generator and it was smaller. How much, IDK. They are in the market for an additional unit to purchase, I'm glad they had this educational experience before that decision was made.

 

[kwired]

It might not be so much that the generator is too small, but that the prime mover can't respond to the surge well enough.

Utility power has an enormous flywheel in comparison and rides through starting surges much better then any smaller generating unit.

 

[zbang]

It might not be so much that the generator is too small, but that the prime mover can't respond to the surge well enough.

Could also be a different or slower governor, or the generator fighting with VFD harmonics. Either way, a bigger generator is a good solution.

 

[Barbqranch]

Another option to buying a generator is to get a PTO generator that uses a tractor as the prime mover.

 

[kwired]

Another option to buying a generator is to get a PTO generator that uses a tractor as the prime mover.

Oversized tractor can result in using a lot more fuel.

I once saw a PTO shaft that had a universal joint in the shaft break when the generator it was driving had a line to line fault occurred on the connected wiring, probably wouldn't have happened if it were being driven by a tractor with closer power rating as the generator rating.

 

[ptonsparky]

Oversized tractor can result in using a lot more fuel.

I once saw a PTO shaft that had a universal joint in the shaft break when the generator it was driving had a line to line fault occurred on the connected wiring, probably wouldn't have happened if it were being driven by a tractor with closer power rating as the generator rating.

This company Is way beyond tractor driven geenerators. The power unit(s) they have also provide backup power for their refrigeration as needed.