My phase converter is based on a 10 hp, 200 volt 3 phase motor (odd voltage, but it was cheap).
I have a 10 hp 3 phase compressor that I run once in a while off that phase converter and when the starter on the compressor kicks in the phase converter slows noticably and almost grunts.. With smaller motors the effect is not noticeable. A spinning 3 phase asynchronous motor will act as a generator briefly when a load (like a another motor) is placed on the same line. That is why a "rotary phase converter" is preferable to a "static phase" converter. The rotary phase converter rotors flywheel effect helps start up the motor you are trying to start. I used to do short circuit and breaker coordination studies on General Motors electrical power systems ( my college thesis was on that subject - this was just after the stone age) and spinning motors contributes greatly to short circuit currents during a system fault as they all turn into generators temporarily and pump current/power back into the power lines. Dave On 5/31/2012 11:08 AM, ceen...@in-front.com wrote: > Hi Dave, > > I have not found that the rotary phase converter slows in RPM during high low > demands as it is still an asynchronous AC motor and is there is no torque > demand on the motor shaft. I don't think a flywheel would help here. If it > were physically connected to a 3-ph generator it would be another story and > the 15HP motor would look more like a 10HP from a shaft stand point when run > from single phase. > > A larger rotary phase converter would help though. Sounds like your machine > is sensitive enough that a 25-40HP rotary phase motor may be be necessary to > get the impedance closer to that of the grid. Adding more 3-phase motors to > the system lowers the impedance of the WYE and helps to stabilize the wild > leg as demonstrated with the lathe motor. I'm entertaining the thought of > adding a 15HP motor to mine if I find a cheap one. > > > Dennis > > > >> -------Original Message------- >> From: Dave<e...@dc9.tzo.com> >> To: emc-users@lists.sourceforge.net >> Subject: Re: [Emc-users] Commutating Reactor >> Sent: May 31 '12 09:43 >> >> You are probably right. When the drive load surges it is likely faulting >> out on what it thinks is a lost phase or phase undervoltage. >> >> It might be interesting is to run this test again and put a clamp on >> ammeter on each leg feeding your Mill and see how balanced the currents >> are. >> >> I have never really had any problem with my phase converter running >> loads so I haven't paid much attention to it, but I think I only have >> run capacitors connected between one phase and the made up phase. I >> know I don't have any >> between both of the two original phases. I was always more concerned >> about the current balance between phases than voltages. The voltages >> have always been within reason ( as I recall ). But then this is one >> of those things that I don't pay much attention to unless it isn't working. >> >> I suspect that the 611 is expecting a stiff power supply - which most 3 >> phase services can provide. If you have a large pulley you can attach >> to your phase converter motor shaft to add inertia to the rotor, you >> might want to attach it. It would help the motor supply surge current >> to the 611 drive. >> >> Dave >> >> >> > ------------------------------------------------------------------------------ > Live Security Virtual Conference > Exclusive live event will cover all the ways today's security and > threat landscape has changed and how IT managers can respond. Discussions > will include endpoint security, mobile security and the latest in malware > threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
