'X starts per hour' means - unless additional data are specified - X starts equally spaced within 1 hour (first start when the motor is cold); in case 6 starts = each next after 10 min. Generally, the same applies to LV, MV or HV machines.
There is do direct relation between number of starts...
With insulation resistance on several GigaOhm level, PI value is not so essential as in case when IR is eg.hundreds or dozens of MOhms. With your IR values and PI=1,33 I wouldn't concern much about the insulation condition (esp. if this is not a new machine).
Typical shell surface loads for RENK (or similar) sleeve bearings are 1-2 N/mm2 (actual values depend of course on speed, lubrication etc.), calculated as follows:
p=Fr/(DxB)
p - bearing surface load [N/mm2]
Fr - radial load on the bearing [N]
D - bearing shell bore / shaft journal diameter...
HCBFlash: the generators have sleeve bearings.
181273: Are the DE bearings of ZFZLA type (with round tilting thrust pads)? These bearings have separate oil connections for radial part and for both axial (thrust) parts. Is the oil circulation OK, esp. for the thrust parts?
Some additional information:
Since resistance method gives average winding temperature, and ETD method - (theoretically) temperature in hottest poits of the winding, for the latter method limits of temperature rise are higher by 5-10 K (depending on machine output, acc.to IEC60034-1).
Acc to a/m...
I think it's not necessary to change the rating plate of this motor for using it with new pump. Motors are hardly ever operated exactly at rated load (normally less, but - if thermal margin allows, as in this case - can be 'overloaded' as well). If this could be useful for maintenance, I'd...
Hi,
I have a question regarding meaning of "runaway speed" requirements specified for hydrogenerator sets. My doubt refers to the duration usually specified together with runaway speed value (eg. 200% of rated speed during 10 min.). I've never seen additional information about limitation of...
For the new, epoxy impregnated insulation I would expect much higher resistance value than 100 MOhms, as stated (if measured in cold state) - so it might suggest something wrong in insulation/impregantion process. Maybe the rotor's drying before impregnation was insufficient?
I think it's a kind of misunderstanding: if we're talking about genset with synchronous generator (am I right?), rated p.f. of 0.8 is lagging p.f., ie. generator delivers reactive power to the system. Change of generator p.f. is possible by regulation of excitation current: to increase p.f. to...
To motorspert:
This 'formula' is rather strange...
Motors of 710mm shaft axis height may have output of several MW, with total losses well over 100 kW (which mean heating of surroundings - unless the losses are carried away by cooling medium, eg. water).
Our customer informed us about failure of cage motor, that was recently repaired in our workshop (630 kW, 6 kV, 50 Hz, 1500 rpm, TEFC). D-end bearing failure happened after ca. 6 weeks of continuous motor operation and – since the user did not apply remote vibration- nor temperature monitoring...
boscorio,
Pls verify what are the dominant vibration frequencies (measured on supplied motor).
You mentioned that “The freq of the vibration was primarily at 1x of running speed 515 RPM, hence, 515 Hz” – but for the 12/14-pole motor at 60 Hz the rotation frequency is respectively 10 Hz (speed...
Hello Suntop.
What was the bearings condition stated after disassembling the motor (ie. if any traces of bearing failure was noticed)?.
If bearings themselves are OK, you should check possible axial clearance (play) of the rotor in relation to stator. In some operating states of the pumps, axial...
We recently carried out checking measurements on two HV cage motors (4000 HP) after their rewinding (VPI process). What surprised us, is that capacitance of stator winding insulation is very high – ca.100 times higher than in previously rewound motors of the same type. But all parameters taken...
