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Besides more ripple at the output voltage, you will see significant drop at the power output of the rectifier. If the motor and its loads force rectifier to go out of this new power capability zone, then you may start to see overcurrent failures on both rectifier and motor side.

If you can generate variable frequency PWM in HC11, you can feed this signal to an RC to filter high frequency components. The output of RC filter will be sine wave, In fact this is the simplest DAC tecnique used in some microcontroller as you might aware.

Regarding first part of the problem (low-load motor fed by VFD): If the motor operates in constant torque region, VFD keeps the flux constant unless special precaution is taken in the drive. So this means at low load the motor flux which is an indicator of the power factor will be the same as...

Hello everbody, I need some fundamental information about mobile welding machines. They run from small rechargable battery and are capable of doing small welding jobs requiring 4-5 electrodes without using main power. Thanks in advance

eaglet: After second reading your post, I understand you have got 2 set of 3phase in the motors. If this is the case, unavoidable unbalance occurs between phase leakage reactance. Because one set will occupy lower part of the slots, the other set will occupy upper part of the slots. The one...

As long as you do not change the phase order (not to cause direction reserval), the same phase winding will be excited with the same phase voltage. I would try two times phase order change so that direction will not change. This may help to understand the nature of the problem.

Suggestion for previous posting: Current control is an inherent feature in a permanent magnet DC motor based system. Controller and current regulator will always make sure current will not exceed certain prescribed level while they shape the current as sinusoidal or trapezoidal. So we should...

If you do not care the efficiency so much, then going with the dynamic brake is much cheaper and simpler than regeneration which requires controlled AC/DC interface. Whereas Dynamic brake approach is to connect proper resistance across DC bus during reversal. Speed reversal takes place in two...

The difference between brushless DC and induction motor becomes sharper when we talk about efficiency and reliability issues. Other performance requirement will be satisfied one way or other as long as they are controlled properly. For example frequent direction reversing related temperature...

It is not clear what you meant by qualification testing. However, as a rule of thumb, while you are playing with voltage and frequency simultaneously, you have to keep V/f ratio constant. If you let this ratio increases, then the motor will be saturated and generate less torque but more heat...

KW is "used" portion of KVA. KVAR is the "circulating" portion of KVA. A factor which is called as power factor determines this sharing. Less circulating energy(kVAR) results more usable energy(kW). Because their vectoral sum (KVA) is constant for any given machine.

Ke is called as back emf constant. It indicates the relation between motor speed and induced back emf. Ke will help you determine motor armature current at certain speed such as I=(Applied Vdc- Ke*speed)/R_armature. This equation ignores field current. If you ignore I*R_armature then your...

jcorb5 First of all, you should determine what kills the diode. is it over current or over voltage. From the number you have given, both are possible. Over current and related over temperature kills diode quitely but over voltage kills it with an explosion. This might be the clue. If over...

jghrist Yo are somewhat right. But I am not satisfied how you come up with 8kW. In an almost 400kW low voltage distribution system, 8kW loss is too small.

37pw56gy: Depending on the size of the coil resistance, inductive effect of the coil resistance will create another di/dt effect. Some applications may require another clamping diode accross resistance. So bottom line, well sized diode would be better solution.

KVA is a unit for Power whereas kWh is a unit for energy. Power is consumed energy in a given unity time. And energy is the summation of the power over certain time period. If certain work needs certain energy, powerful person makes it in shorter time period than weak person. However they...

Jbartos, I agree with you. However, if the application does not care or tolerate to the reduced secondary voltage level, the idea is still applicable. By " does not care", I mean no load operation of the transformer.

Kolo; No load loss in the transformer is approximately core losses which are related with the flux level in the transformer core. Flux level is proportinal with primary voltage level. If I were you I put a solid state voltage controller on primary side and reduce voltage level when there is no...

Kolo We do not want to transfer power with the transformer. It will act almost like a current transformer. So its power rate does not need to be that high. The only concern can be the saturation of the transformer core due to high DC current. But this can be eliminated by introducing air gap...

Have you checked IEEE 115-1983 and 115A-1987 standards for synchoronous machines?