Stator core of that era will be hot rolled silicon steel with higher loss than the later day low loss cold rolled steel. So, core was most likely changed.
I doubt the 300 RPM rotor can withstand centrifugal forces at 720 RPM, so possible new rotor, bearings and bearing supports.
Stator winding...
"The rest of section 7.6.5 indicates that some hydro units remain online without excitation for long enough to manually restore the excitation system."
Manually intervene is the key point here. If your machine ran for 15 minutes with no operator action, better to check the rotor health.
IEEE 492
7.6.4 Asynchronous operation (field maintained) - (I have personally seen a 50 MW hydro machine completely destroyed in this operating condition)
Operation of a generator out-of-synchronism with partial or full-field excitation maintained, places the most severe type of duty on the...
OP said 4 x 240 V x 1000 W heaters with 3 terminals suitable either for 240 V or 120 V. If there is another connection possible for both 240 V and 120 V, please post here.
Yes, 62.5 W for each heater and 250 W in total. Which is what I find in large motors. It's enough to keep the motor warm.
V/Hz is set correctly in open loop. Drive is set for PM synch motor mode.
In open loop, the motor had odd electromagnetic noises on top of high current. In closed loop, low current and smooth running.
Guess, PM synch motors are odd beasts.
The brake operates mechanically by springs in case of power loss/stop to hold the hoist in position. The DC supply releases the brake (by pulling in the springs) when the hoist is moving up/down.
After seeing the excellent performance of my new 60 ton EOT crane which came with VFD's for...
Lionel - Yes, the custom designed drive is set for PM mode.
Bill - The very idea of VFD is to have constant flux density V/Hz through the entire speed range.
We ran a 490 V, 2095 KW, 3000 A, 100 RPM Permanent Magnet rotor motor on no-load via a VFD.
In open loop, the motor no-load current is 210 amps while in closed loop (with shaft mounted encoder), it is only 16 Amps.
Why this vast difference between open loop and closed loop currents?
Edit: It's...
No, you cannot detect rotor ground fault without sliprings. Rotor can run with single earth fault but will have damaging vibrations if it develops a second earth fault.
Loss of excitation is harder to detect and will not detect rotor earth fault.
Is it monobloc or separately coupled? Is it vertical or horizontal? Post a few pictures and the nameplate.
Most likely, the generator rotor has interturn shorts if the vibration starts only when the generator is excited.
Output KW = √3 x Input voltage x Input current x power factor x efficiency = √3 x 0.38 x 336.9 x 0.87 x 0.959 = 185 KW
Input KW = Output KW / Efficiency = 185/0.959 = 192.9 KW
Bill
This beast weighs 42 tons. There are also similar low speed synch machines with higher power rating up to 3.5 MW.
Power to weight ratio is pathetic in such low speed machines. I was told they used a 300 ton mobile crane to bring this machine to the ground level.
"Unless you use conversion to DC and then Pulse Width Modulation to get grid frequency AC."
Yes, it's done for wind generators all the time. A 1.5 MW, 15.6 Hz PM Synchronous wind generator in our shop right now, which is connected to 50 Hz grid via inverter. There are many such generators in...
Coco
It so happens we are now rewinding a 64 pole, 2.1 MW, 100 RPM, 53.3 HZ Permanent Magnet Motor synchronous motor. The PM rotor pic below.
You can google Oswald Elektromotoren GmbH and ask them about your PM synchronous generators.
Jeff,
The issue is 475 KW at 2200 RPM. Other speeds have proportional KW.
There is no shaft mounted fan and hence no increased windage loss.
The motor reached 1500 RPM at 25 V, 50 Hz in open shaft run and rotor rotational loss was a few watts only.
That's a lot of current THD.
Any reason to go for 440 V motors when the incoming source is already 550 V?
Rewind the motors to VFD duty 550 V with lower current handling and get rid of transformer, which is one more component to maintain and one more source of failure. Or use the transformer...
