ac to dc power2

[totl]

very unskilled in electronics but a fast learner. I have a PM AC motor that in free spin registers 5-150 volts in 3 phase. I've switched to DC with a 3 phase rectifier but under a load such as checking amp draw the voltage reduces dramatically as the motor slows down.
Looking for a solution to realize about 50 volts DC with 10-15 amps consistently. I have to mention that the drive for this motor is going to be wind at anywhere from 30-70 mph average so the input voltage will vary. Is this possible? Any suggestions?

 

[totl]

ac to dc power

very unskilled in electronics but a fast learner. I have a PM AC motor that in free spin registers 5-150 volts in 3 phase. I've switched to DC with a 3 phase rectifier but under a load such as checking amp draw the voltage reduces dramatically as the motor slows down.
Looking for a solution to realize about 50 volts DC with 10-15 amps consistently. I have to mention that the drive for this motor is going to be wind at anywhere from 30-70 mph average so the input voltage will vary. Is this possible? Any suggestions?

 

[Dragon Tamer]

So you have a 3 phase motor that is running off of 5 to 150V? Last time I checked an AC motor could not run off of DC. The DC will need to be converted to AC before the motor will operate properly.

 

[totl]

ac to dc power

maybe I'm not stating correctly. The motor I have is a permanent magnet ac motor which I am using as an alternator. It has 3 legs coming from it which I have connected to a 3 phase rectifier to obtain dc power which I need. This motor has a squirrel cage fixed to it which when spun freely shows ac voltage from 0 on up depending on the RPM. Through rectification to dc I have a small drop in voltage but when current is drawn the voltage drops considerably as the RPM decreases. I need the dc input to maintain its voltage without decreasing as current is drawn. The output voltage can be fixed or dependant on the input voltage but I need higher voltage with lower amps.

 

[Dragon Tamer]

Oh, you didn't mention that you were using it as an alternator. If you are using the just the rectifier and measuring the DC voltage, of course it is going to drop. Especialy if you increase the frequency. You have not filtering on the rectified output to stabelise the voltage. In a car, the battery usually stabalises the output. If you are not using a car then you will need a fairly large cap if you plan on powering a signifigant load. Right now all you are measuring is the average voltage through the load, when the frequency of the output increases, the amount of time that the voltage actually stays at the load free measure decreases rather rapidily.

It may also be possible that your motor is not capable of operating backwards. Most motors can but the acutal current that you get from them will often be very different than the current that they require to run.

 

[Reloadron]

Much of what you are asking depends on the motor you are using as a generator. The name plate data would help. There is a good possibility the motor you are using as a generator will not give you what you want. From what you say the motor is behaving as expected when a load is applied.

Ron

 

[totl]

So a capacitor doesn't put a load on the source but stores energy as a battery? Is any other curcuitry necessary to utilize this stored dc power and can the amps or voltage output be increased or at least consistent? I have looked at dc - dc boost converters and they look promising but I don't know enough about this to make that call. So far I haven't spent any money as the motor was free - still good though - and I would like ideally to make this project from spare parts if possible. The motor is a GE ecm motor which has a detachable component with curcuitry that converts incoming 230 volt ac power to dc voltage for the control board - this an air conditioning blower motor - then back to ac for the motor. After talking to you I see that it is possible that I have what I need right here. There are 2 curcuits - one has what I believe to be caps on it along with a doughnut shape device that is coiled in copper wire. The other has what I believe are transistors - based on pictures I've seen - with a connection for the motor and a connection for the control board in the air handler. The caps say 1000uf and 200wv on them. Any thoughts?

 

[totl]

ac to dc power

I'm not sure what happened to my initial thread. I was posting a reply and hit quick reply and I don't see the thread in this forum any more. Any ideas?

 

[meowth08]

Maybe your thread contains things not suitable to be posted. If it's not the case, maybe you can ask those on the chat room.

 

[Reloadron]

Was it the thread about an AC PM motor being used as a generator? Something along those lines? I ask because I think I left a reply and you are right, the thread seems to have vanished and your post count in this thread is 1? Strange. You may want to contact a moderator and see what happened. The thread seemed fine to me but then again... Check with a moderator.

Ron

 

[totl]

ac to dc power

yes it was an ac pm motor thread. nothing objectionable in it. how do I contact a moderator?

 

[ericgibbs]

yes it was an ac pm motor thread. nothing objectionable in it. how do I contact a moderator?

hi,
You caused a small problem by starting two threads on the same Topic with the same Title..

Your two threads are now merged.

Moderation. E

 

[totl]

ac to dc power

sorry, I'm not familiar with this yet. Forum challenged.

 

[totl]

ac to dc power

what is meant by 1000uf and 200wv which I see on what I believe are capacitors?

 

[Reloadron]

Thank you Eric and that mystery is resolved.

what is meant by 1000uf and 200wv which I see on what I believe are capacitors?

That would be a capacitor. The 1000 uF is the capacitance (value) of the capacitor expressed in Micro Farads and the 200 WV is the maximum Working Voltage of the capacitor. However, capacitance is not used as a load in what you are trying to do. Again, the nameplate data from the motor would help considerably. Including voltage, current, RPM, and HP would be nice to know.

Ron

 

[totl]

ac to dc power

The motor is rated as 1 ph, 60hz, 3/4 hp, 120/240 v @9.6/6.8 amps, 0-1400rpm

 

[Reloadron]

The motor is rated as 1 ph, 60hz, 3/4 hp, 120/240 v @9.6/6.8 amps, 0-1400rpm

OK and this was your original post:

ac to dc power2

very unskilled in electronics but a fast learner. I have a PM AC motor that in free spin registers 5-150 volts in 3 phase. I've switched to DC with a 3 phase rectifier but under a load such as checking amp draw the voltage reduces dramatically as the motor slows down.
Looking for a solution to realize about 50 volts DC with 10-15 amps consistently. I have to mention that the drive for this motor is going to be wind at anywhere from 30-70 mph average so the input voltage will vary. Is this possible? Any suggestions?

The data you just provided mentions a single phase motor but your initial post calls out a 3 phase motor and you used a 3 phase rectifier. That leaves me lost? A single phase motor would have 3 leads exit the motor. Line, Neutral and Ground. If using it as a DC generator (assuming it can be used as one) you would place a full wave bridge rectifier across the Line & Neutral lines with the AC input to the bridge being those lines. You are sure this is an AC motor as some things don't make sense?

According to the data you have a 3/4 HP motor which at full load (120 volt configuration) would draw 9.6 amps or about 1,152 watts. It runs at 1400 RPM maximum speed. In a perfect world 1 HP = 746 watts so 3/4 HP would = about 560 watts. The rest is loss. We won't even get into torque.

While I understand you are new to all of this I don't see what you have doing what you want to do. Maybe I am wrong and another forum member has some thoughts.

Ron

 

[totl]

ac to dc power

Again I am probably mistating this. There are 3 leads going into the motor. I don't know if they are hot, neutral and ground - this is a variable speed motor if that makes a difference -
but when spinning the motor backwards any combination of the three shows ac voltage when I use my multi-meter. I am probably wrong in assuming that it is 3 phase because of this. When rectified it shows a little less voltage but I still need to maintain that voltage with little drop when under load.