Search results for query: *

Thanks dArsonval, Your lines describing such situation are here probably even more accurate than you know :-). Sorry for still picking on this, but I cannot figure out why amature and collector are completely destroyed - significant brush sparking for sure happend but the commutator, brushes...

Thanks edison123, The amature is destroyed and needs complete renewal. I am looking for information if this polarity mix-up related to the interpoles could actually cause such severe damage to the amature. The commutator and the brushes show for sure signs of sparking but they are not destroyed...

Hello, We have a 150HP DC motor where the interpoles after overhaul were connected with wrong polarity. Half an hour after start the motor drive tripped and the amature suffered catastrophic overheating in the area just after the commutator, I believe it is where the windings are being...

If somebody has a suggestion where to find a generator somewhat smaller/less heavy than the automobile generator, I will still appreciate a hint. The size and power of the typical automobile generator is on the edge of what my "lab" can handle. Kind regards

Yes, a quick research also showed me that generators for motorcycles often have PM'sm. I am going to drive the generator by a DC motor. My intention is to try to derive all the typical data sheet parameters available for much larger power generators. This includes both steady state parameters...

Hi, thanks for that advice. I was not aware that automotive generators are 3ph with sliprings. I will look for a generator for a motorcycle to get as small as possible.

Hello, For test and educational purpose I need a small 3-phase AC synchronous generator. The generator shall have rotor windings with slip rings/brushes for excitation control. Exact size does not matter, could be a few hundred watts or less. Have any seen such a kit around or perhaps a...

Hi, Wonder if one of you guys have been facing similar "problems": I am modeling automatic voltage regulators and excitation systems for smaller synchronous machines. Size is typical 3-10MW, and the machines are 10-15 years old. One of my main problems is how to derive the parameters for the...

Dear friends, We have a transformer, 3000kVA - step-down 6kV/0.4kV - cast resin - insulation class F. Right now it is running at winding temp 130 deg. cel. (full load - PT100 embedded measurement). Ambient temperature is 20 deg. cel. Ambient temperature is expected to reach approx. 35. We...

Hi Mark, Yes, the power factor increases - and peaking at max T seems fair. But still: the increasing PF will increase voltage drop, according to previous formula. At the same time current is reduced because rotor-slip is reduced. So my original question is still open. rbulsara: I think we are...

formula: dU= sqrt(3) x current x (cable_resistance x cos_phi + cable_reactance x sin_phi) phi = phase angle of current JP

rbulsara - very fast reply, thanks. But: Power factor has, as far as I can calculate, a large impact on voltage drop. If assuming PF=1, then voltage drop will be in phase with supply voltage, ie a large drop. If assuming PF=0, then voltage drop will be displaced 90 deg from supply voltage...

Hi (again), We are installing a 150kW induction motor, for a lifting device. Motor has to start on full load torque. The terminal voltage must not drop too much during start, to ensure enough torque. My problem is how to calculate max. voltage drop. Voltage drop will of course depend on...

Hi, Check out Analog Devices - ADMC401 is prepared for motor control applications.

davidbeach, just some thoughts from here: consider a transformer-starting induction motor. With such installation (large machines) it could be useful to energizer transformer and motor in one step? If this is practiced in real transformer starting motor installations, I can not answer you...

Considering pete's #3: If transformer is loaded on secondary when primary is energized, this may in fact reduce the inrush current magnitude and/or reduce the inrush time? Brgds Petersen

Hi, We have an impressed current cathodic protection of a steel structure in seawater. I found that the main electrical resistance exists in the vicinity of the anode. Driving voltage is +50 V at anode, cathode voltage is 0 V. Can anyone give a hint how to model an circular anode in FE software...

Hi, Could anyone tell why a 3-phase power transformer shows a so nonlinear and high inrush current characteristica, when induction motors do not. Of course induction motors do have a high (4-8 x In)starting current, but it seems low compared to transformer inrush of 10-20 x In. The electric...

Electricpete, if you intend to request a vibration check for your motors in loaded condition, would you specify/use the same limits as for unloaded test? Weh3 is speaking the motor manufacturers point of view - "Can the standard take into account all possible loading conditions?" and further...

Thanks for a prompt reply, agree with you to some extend. But what if thermal heating of the rotor, during load, for some reason causes bending of the rotor, resulting in high vibrations. Rotors are usually balanced dynamically in cold condition. What if vibrations in load condition is severe...