Miami Boat Electrician
New member
Dear colleagues, here we have a very interesting maze, puzzling.
Please, Have you experienced single phase capacitor motors cogged by harmonics ?
This case happens on a Yacht with two big independent generators, not electrically paralleled, nor mechanically interconnected; So a slightly different frequency 3 hz and voltage 3 % are cycling between the two generators.
The two identical generators are feeding different panels, not clashing, but two generators neutrals are grounded on their own frame, and safety ground interconnects all metal components and frames on the yacht for the GFCI Protection system.
I suspect that unbalanced loads are returning to each generator through its own neutral, and finally on their commonly grounded frames to the whole yacht bonding system….. Which may be creating harmonics and displaced neutrals.
There are 6 main circuit panels, that can be feed by a random combination from 3 sources:
Gen 1, OR Gen 2, OR public network (this last only when the yacht is connected through its shore power cord to the dock)
Six manual switches (rotative drum) are used to feed each panel from the desired source. Manually.
Auto starting the 2nd generator, Synchronizing and Paralleling them may help to unify frequencies and voltages along independent panels; but it will continue to be a challenge to keep dynamically balanced phases under variable loads.
A conversation with the manufacturer after studying the yacht electric diagrams would be necessary.
=========================
For the air conditioning System, The yacht has 3 chillers electrically feed from different panels, ( and different generator), as well as a dozen single-phase motor’s fans for several rooms.
In the simplest HVAC system most likely there is only one unified pipeline loop, one chilled water pump (without variable-flow), and no solenoid regulating valves.
The temperature control may begin with 3 chillers
cycling their compressors, and end on each remote fan with independent speed and temperature control.
Different chillers and different fans are feed from different circuit phases from a different panel and generator……with unbalanced neutral voltages and frequencies, creating harmonics that interfere with some boat devices.
===========================
Out of the 12 remote fans, only two are presenting problems, they are connected on the same circuit, panel and generator;
When the controller pauses or varies the fan’s speed, randomly the fans get cogged and buzzing, simultaneously ( not crawling, but zero rotation) and after some minutes they suddenly resume running… simultaneously. All other fans on the system are working well .
Been a typical indication of Capacitor failure, ( but simultaneous failure, so I discarded it. Any how replacement was made without good results.
The Fans oddly do cogg, buzz and after some minutes restart simultaneously.
It could be an internal winding overheat disconnecting after the cogging, as surprisingly the startup winding hasn’t burnt its insulation yet.
Next conclusion will be a low voltage regulation when both try to restart on the same circuit, been unable to overcome the load…..but this is discarded because it only happens while both generators are operating and supplying the yacht energy.
The failure doesn’t happen when the energy is sourced from the public network, also doesn’t happen when only one generator is operating.
My conclusion is that it is related to 5th and 7th harmonics, and/or unbalanced phases, and thought about purchasing an oscilloscope, to check that negative sequence torque. But that is quite expensive.
Probably by adding a small isolation transformer, a regulator or a Harmonics filter by each fan’s start capacitor would be simpler, and a full clean beginning.
The harmonics in addition than produced by the generators, may also be produced in the motor’s airgap between rotor and stator, so filters may not work.
Please, share with me any experience or thoughts of how to solve.
Thank you
Please, Have you experienced single phase capacitor motors cogged by harmonics ?
This case happens on a Yacht with two big independent generators, not electrically paralleled, nor mechanically interconnected; So a slightly different frequency 3 hz and voltage 3 % are cycling between the two generators.
The two identical generators are feeding different panels, not clashing, but two generators neutrals are grounded on their own frame, and safety ground interconnects all metal components and frames on the yacht for the GFCI Protection system.
I suspect that unbalanced loads are returning to each generator through its own neutral, and finally on their commonly grounded frames to the whole yacht bonding system….. Which may be creating harmonics and displaced neutrals.
There are 6 main circuit panels, that can be feed by a random combination from 3 sources:
Gen 1, OR Gen 2, OR public network (this last only when the yacht is connected through its shore power cord to the dock)
Six manual switches (rotative drum) are used to feed each panel from the desired source. Manually.
Auto starting the 2nd generator, Synchronizing and Paralleling them may help to unify frequencies and voltages along independent panels; but it will continue to be a challenge to keep dynamically balanced phases under variable loads.
A conversation with the manufacturer after studying the yacht electric diagrams would be necessary.
=========================
For the air conditioning System, The yacht has 3 chillers electrically feed from different panels, ( and different generator), as well as a dozen single-phase motor’s fans for several rooms.
In the simplest HVAC system most likely there is only one unified pipeline loop, one chilled water pump (without variable-flow), and no solenoid regulating valves.
The temperature control may begin with 3 chillers
cycling their compressors, and end on each remote fan with independent speed and temperature control.
Different chillers and different fans are feed from different circuit phases from a different panel and generator……with unbalanced neutral voltages and frequencies, creating harmonics that interfere with some boat devices.
===========================
Out of the 12 remote fans, only two are presenting problems, they are connected on the same circuit, panel and generator;
When the controller pauses or varies the fan’s speed, randomly the fans get cogged and buzzing, simultaneously ( not crawling, but zero rotation) and after some minutes they suddenly resume running… simultaneously. All other fans on the system are working well .
Been a typical indication of Capacitor failure, ( but simultaneous failure, so I discarded it. Any how replacement was made without good results.
The Fans oddly do cogg, buzz and after some minutes restart simultaneously.
It could be an internal winding overheat disconnecting after the cogging, as surprisingly the startup winding hasn’t burnt its insulation yet.
Next conclusion will be a low voltage regulation when both try to restart on the same circuit, been unable to overcome the load…..but this is discarded because it only happens while both generators are operating and supplying the yacht energy.
The failure doesn’t happen when the energy is sourced from the public network, also doesn’t happen when only one generator is operating.
My conclusion is that it is related to 5th and 7th harmonics, and/or unbalanced phases, and thought about purchasing an oscilloscope, to check that negative sequence torque. But that is quite expensive.
Probably by adding a small isolation transformer, a regulator or a Harmonics filter by each fan’s start capacitor would be simpler, and a full clean beginning.
The harmonics in addition than produced by the generators, may also be produced in the motor’s airgap between rotor and stator, so filters may not work.
Please, share with me any experience or thoughts of how to solve.
Thank you
