Three-phase alternating current generated by one phase alternating current?
Physikfan, Thu Apr 20 2017, 07:43AMFor the motors of my vacuum pumps I need 400V three-phase current (1-2 kW), but unfortunately I have not such a current source in my home.
I see three possibilities:
1. I could use a capacitor to establish a phase shift for a "third phase".
2. I manufacture a circuit according to an already proven circuit diagram with IGBTs.
3. I purchase a commercial ready circuit or device with housing via Ebay.
Please, who can give me good advice?
Re: Three-phase alternating current generated by one phase alternating current?
Sulaiman, Thu Apr 20 2017, 08:05AM
something like this
EDIT: inserted after reading the post below
the cost, weight, size of passive components, or a motor-generator set, required for 1 - 2 kW make a VFD attractive
the starting torque of a vfd is adjustable to greater than nominal
a VFD has many benefits, and uses
Sulaiman, Thu Apr 20 2017, 08:05AM
something like this
EDIT: inserted after reading the post below
the cost, weight, size of passive components, or a motor-generator set, required for 1 - 2 kW make a VFD attractive
the starting torque of a vfd is adjustable to greater than nominal
a VFD has many benefits, and uses
Re: Three-phase alternating current generated by one phase alternating current?
Dr. Slack, Thu Apr 20 2017, 08:11AM
Ideally you would use a capacitor and an inductor, and may need a transformer as well for amplitude changes. This sort of phase shifter only works well for a small range of loads, but is quite respectable over a 2:1 range.
Once a 3 phase motor is started, it will often run surprisingly well on a single phase. Depending on what static load the pump puts on your motor, you may or may not be able to start it with a simple phase shifter, and then disconnect it for running.
One type of single to 3 phase converter that is commonly used is a large 3 phase motor, run off load. It's started with a simple phase shifter, and then run from a single phase. You take the three phase supply from its terminals.
Obviously a VFD (variable frequency drive) will do the job properly, giving your motor full starting and running torque.
It really depends on how over-specified your vacuum pump motor is, how well it will tolerate short-cuts in powering it.
Dr. Slack, Thu Apr 20 2017, 08:11AM
Ideally you would use a capacitor and an inductor, and may need a transformer as well for amplitude changes. This sort of phase shifter only works well for a small range of loads, but is quite respectable over a 2:1 range.
Once a 3 phase motor is started, it will often run surprisingly well on a single phase. Depending on what static load the pump puts on your motor, you may or may not be able to start it with a simple phase shifter, and then disconnect it for running.
One type of single to 3 phase converter that is commonly used is a large 3 phase motor, run off load. It's started with a simple phase shifter, and then run from a single phase. You take the three phase supply from its terminals.
Obviously a VFD (variable frequency drive) will do the job properly, giving your motor full starting and running torque.
It really depends on how over-specified your vacuum pump motor is, how well it will tolerate short-cuts in powering it.
Re: Three-phase alternating current generated by one phase alternating current?
radiotech, Thu Apr 20 2017, 11:11AM
If you have several motors, an artificial three phase stem may be set up.
Search Phase converter.
System works well. I have set up a few over the years.
You must know your motors well.
radiotech, Thu Apr 20 2017, 11:11AM
If you have several motors, an artificial three phase stem may be set up.
Search Phase converter.
System works well. I have set up a few over the years.
You must know your motors well.
Re: Three-phase alternating current generated by one phase alternating current?
klugesmith, Thu Apr 20 2017, 06:41PM
+1 on what Dr Slack and Radiotech both mentioned. Often called "Rotary phase converter". It's been traditional in amateur shops for many decades. My friend Tom has one to run his milling machine and lathe. No semiconductor parts required.
Here are a couple more DIY-oriented links:
"how-to-build-a-rotary-phase-converter"
"projects/Phase-Converter":
To begin, you would scrounge a three-phase induction motor. "... called an idler, and needs to have a 20-30% higher horsepower rating than the largest equipment motor that you will be using".
p.s. long ago my employer needed to test a 25 kW product on 50 Hz power, before shipping it to a customer in Europe. We had no shortage of three-phase power at 60 Hz. Rented a rotary frequency converter, aka a motor-generator set. Speed ratio set by a v-belt connection.
Others have mentioned solid-state Variable Frequency Drive units, which commonly have three-phase outputs. VFD's that come with three-phase AC inputs can usually be used on single-phase power. Vacuum pumps with 50/60 Hz motors will suck faster at 60 Hz.
klugesmith, Thu Apr 20 2017, 06:41PM
+1 on what Dr Slack and Radiotech both mentioned. Often called "Rotary phase converter". It's been traditional in amateur shops for many decades. My friend Tom has one to run his milling machine and lathe. No semiconductor parts required.
Here are a couple more DIY-oriented links:
"how-to-build-a-rotary-phase-converter" "projects/Phase-Converter":
To begin, you would scrounge a three-phase induction motor. "... called an idler, and needs to have a 20-30% higher horsepower rating than the largest equipment motor that you will be using".
p.s. long ago my employer needed to test a 25 kW product on 50 Hz power, before shipping it to a customer in Europe. We had no shortage of three-phase power at 60 Hz. Rented a rotary frequency converter, aka a motor-generator set. Speed ratio set by a v-belt connection.
Others have mentioned solid-state Variable Frequency Drive units, which commonly have three-phase outputs. VFD's that come with three-phase AC inputs can usually be used on single-phase power. Vacuum pumps with 50/60 Hz motors will suck faster at 60 Hz.
Re: Three-phase alternating current generated by one phase alternating current?
Physikfan, Fri May 05 2017, 07:52AM
Next Monday I hope to get "real" three-phase current finally.
I will start the frequency converter next Thursday with a small pump with the help of an electrical engineering specialist, then I will know more.
Physikfan, Fri May 05 2017, 07:52AM
Next Monday I hope to get "real" three-phase current finally.
I will start the frequency converter next Thursday with a small pump with the help of an electrical engineering specialist, then I will know more.
Re: Three-phase alternating current generated by one phase alternating current?
Physikfan, Sun Jun 25 2017, 08:01PM
Hi Sulaiman, Dr. Slack, radiotech and klugesmith
Thanks for your posts.
Meanwhile, I have a working combination of a single-phase fed frequency converter and a three-phase motor.
However, I will not use the pump motor, since I would not necessarily expect the pump to have a wrong direction of rotation and I also have unintended oil fountains already enough.
Exciting will be the experiments with variable frequency, I will also use an oscilloscope to study the corresponding curve forms and phase differences.
Regards
Physikfan
Physikfan, Sun Jun 25 2017, 08:01PM
Hi Sulaiman, Dr. Slack, radiotech and klugesmith
Thanks for your posts.
Meanwhile, I have a working combination of a single-phase fed frequency converter and a three-phase motor.
However, I will not use the pump motor, since I would not necessarily expect the pump to have a wrong direction of rotation and I also have unintended oil fountains already enough.
Exciting will be the experiments with variable frequency, I will also use an oscilloscope to study the corresponding curve forms and phase differences.
Regards
Physikfan
Re: Three-phase alternating current generated by one phase alternating current?
johnf, Mon Jun 26 2017, 09:21AM
These are very common
like
But nobody said cheap unless you have an inefficient large three phase motor lying around to use as an idler
johnf, Mon Jun 26 2017, 09:21AM
These are very common
like
But nobody said cheap unless you have an inefficient large three phase motor lying around to use as an idler
Re: Three-phase alternating current generated by one phase alternating current?
Physikfan, Fri Jun 30 2017, 06:48PM
Hi Sulaiman, Dr. Slack, radiotech, klugesmith and johnf
When a motor is powered by a frequency converter, the pulse-width-modulation (PWM) voltage applied to the motor induces additional magnetic noise at the clock frequency and also a harmonic distortion of the clock frequency.
Therefore it should be possible to detect acoustically wether a three-phase AC motor is driven by a frequency converter or operated by "normal" three phase current.
This would justify measurements with a good microphone and a FFT analyzer.
I will therefore carry out acoustic measurements with such an analyzer parallel to electrical current-voltage measurements.
Physikfan, Fri Jun 30 2017, 06:48PM
Hi Sulaiman, Dr. Slack, radiotech, klugesmith and johnf
When a motor is powered by a frequency converter, the pulse-width-modulation (PWM) voltage applied to the motor induces additional magnetic noise at the clock frequency and also a harmonic distortion of the clock frequency.
Therefore it should be possible to detect acoustically wether a three-phase AC motor is driven by a frequency converter or operated by "normal" three phase current.
This would justify measurements with a good microphone and a FFT analyzer.
I will therefore carry out acoustic measurements with such an analyzer parallel to electrical current-voltage measurements.
Re: Three-phase alternating current generated by one phase alternating current?
Sulaiman, Fri Jun 30 2017, 08:29PM
older drives used audio frequencies for the pwm clock
newer drives with faster semiconductors often have ultrasonic pwm clocks
so an audio microphone may not work.
Smaller drives often rely soley on the inductance of the motor windings to produce a sinusoidal current from the pwm signal
a 'scope can 'see' the switching.
Many drives have output inductors internally so it is difficult to see the switching with a motor connected.
Sulaiman, Fri Jun 30 2017, 08:29PM
older drives used audio frequencies for the pwm clock
newer drives with faster semiconductors often have ultrasonic pwm clocks
so an audio microphone may not work.
Smaller drives often rely soley on the inductance of the motor windings to produce a sinusoidal current from the pwm signal
a 'scope can 'see' the switching.
Many drives have output inductors internally so it is difficult to see the switching with a motor connected.
Re: Three-phase alternating current generated by one phase alternating current?
radiotech, Sat Jul 01 2017, 02:16AM
The sound that three phase induction motors produce is a 50/60 Hz hum added to a lower pitch which
represents the synchronous rate minus the slip. So a 3450 RPM motor, will run at that speed under load.
With no load, it will be closer to 3600.
Motors on invertors sometimes have termination networks connected at the motor. That is to protect
the motor against high voltage pulses, higher higher in frequency than their operating frequency.
Your fft pickup, for both types probably would work better with a magnetic field detector coil placed
close to feeder cable to the motor from the VFD.
In actuality big inverter drives, especially pumps, scream so loudly, hearing protection in required when working close by.
radiotech, Sat Jul 01 2017, 02:16AM
The sound that three phase induction motors produce is a 50/60 Hz hum added to a lower pitch which
represents the synchronous rate minus the slip. So a 3450 RPM motor, will run at that speed under load.
With no load, it will be closer to 3600.
Motors on invertors sometimes have termination networks connected at the motor. That is to protect
the motor against high voltage pulses, higher higher in frequency than their operating frequency.
Your fft pickup, for both types probably would work better with a magnetic field detector coil placed
close to feeder cable to the motor from the VFD.
In actuality big inverter drives, especially pumps, scream so loudly, hearing protection in required when working close by.
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