What causes subsynchronous vibration?
What causes subsynchronous vibration?
The subsynchronous vibration problem experienced on auxiliary turbine was generated by one, or more, of the following mechanisms: 1) Hydrodynamic fluid film bearing (Oil Whip); 2) Excessive clearances in the bearings; 3) Incorrect pinch on the bearings; 4) poor bearing foundation tie-down; 5) Defective coupling; 6) …
What is subsynchronous vibration?
The speed that the shaft moves around the whirl path is called the non-synchronous speed or frequency. If the non-synchronous speed is slower than the synchronous speed, then it is called subsynchronous. The frequency of non-synchronous vibration is often referred to in terms of its whirl frequency ratio.
What is the cause of subsynchronous resonance?
Subsynchronous resonance is a phenomenon in which one or more of the resonant frequencies of the turbine generator shaft in thermal power units coincides through the generator with a natural resonant frequency of the electrical system with long radial transmission network with series capacitors such that there is a …
What is synchronous frequency vibration?
The frequency of synchronous vibrations matches the rotor rotational frequency. A shaft spinning at 3600 rpm (60 Hz) will have a synchronous vibration of 60 Hz. Synchronous vibration is largely caused by imbalance. This orbit shows the rotor rising to a peak after exactly a single rotations.
What is subsynchronous resonance?
What is subsynchronous speed?
In the sub-synchronous mode, series-connected wound-rotor induction motor can run at a speed below the synchronous speed with self-starting capability in a manner similar to that of the normal mode of operation of an induction motor.
What is super synchronous mode?
In super- synchronous mode, the rotor speed is greater than the. machine synchronous speed and slip is negative (s< 0). The. rotor voltage/current sequence has to be reversed to supply.
What is Supersyncronous speed?
Abstract: The name “super synchronous” has been given to a certain type of motor, not because the motor operates above synchronous speed but because it has the ability to develop super torque in starting.
What is the cause of maximum vibration in a motor?
Vibration can be caused by one or more factors at any given time, the most common being imbalance, misalignment, wear and looseness. Imbalance – A “heavy spot” in a rotating component will cause vibration when the unbalanced weight rotates around the machine’s axis, creating a centrifugal force.
What causes Surge in a centrifugal compressor?
One unique issue of centrifugal compressors is surge. Surge is when the compressor back pressure is too great, and momentary flow reversal or recirculation occurs inside the compressor. Surge will typically produce vibration amplitudes at frequencies below running speed (sub-synchronous).
What are the common causes of compressor vibration?
Some of the common causes of compressor vibration that are not specific to any type of compressor are: 1 Unbalance 2 Misalignment 3 Looseness 4 Bearing Issues 5 Resonance / Critical Speeds More
What is the vane pass frequency of a liquid ring compressor?
As expected with positive displacement compressors, the liquid ring compressor creates pressure pulsations. These pressure pulsations cause compressor vibration at a frequency equal to the operating speed times the number of vanes on the impeller. This frequency is known as the vane pass frequency.
What are the different types of rotors on a screw compressor?
Screw compressors have two (2) rotors, a male and female rotor. Typically, the male rotor is the driving rotor and it will have fewer lobes than the female rotor, a four (4) lobe male rotor with a six (6) lobe female rotor is common.
