It is common that someone wants to run an AC well pump off an inverter but the starting current is a problem. Often soft starters or variable speed starter/pump solutions will solve the problem. I stumbled across this video on Youtube and it has a lot of good basic lessons in addition to showing how variable frequency drives work. It is worth watching if you want to learn or reinforce your understanding....hits a lot of topics in electricity.
Variable Frequency Drives (and more basic topics) explained
- Thread starter DThames
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Someone linked to a Grundfos solution with a controller and a pump as a unit. Most likely a 3phase pump on their VFD.
What can be done with a 3ph induction motor and a close loop feedback servo type drive is pretty amazing.
Ampster
Renewable Energy Hobbyist
Yes you have to get the entire system of controller and motor. The controller converters single phase to three phase and varies the frequency. It is becoming more common because of the efficiency. My new refrigerator is an example. I rarely hear it running. The most noise it makes is when I leave the door open.
nosys70
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most of AC and fridge come with a VFC today, They are labelled "with Inverter"
the advantage is that with usual compressor in AC and fridge/freezer is the compressor is just ON or OFF.
but with inverter models, you can run the compressor at 50% if needed and get soft start.
the drawback is there is ton of electronics in these devices and the good old hammer fix does not work anymore.
the advantage is that with usual compressor in AC and fridge/freezer is the compressor is just ON or OFF.
but with inverter models, you can run the compressor at 50% if needed and get soft start.
the drawback is there is ton of electronics in these devices and the good old hammer fix does not work anymore.
Mars
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I have a Grundfos SQ pump, specifically a
5SQ07-270 5 GPM 3/4 HP VARIABLE SPEED PUMP & 2 WIRE MOTOR
It is not a 3 phase induction motor. Here is a snippet from the manual:
"SQ pump models operate at a constant speed much
like today’s conventional pumps. The difference is that
SQ delivers the benefits of an electronically controlled
permanent-magnet motor that cannot be achieved with
a conventional induction motor."
5SQ07-270 5 GPM 3/4 HP VARIABLE SPEED PUMP & 2 WIRE MOTOR
It is not a 3 phase induction motor. Here is a snippet from the manual:
"SQ pump models operate at a constant speed much
like today’s conventional pumps. The difference is that
SQ delivers the benefits of an electronically controlled
permanent-magnet motor that cannot be achieved with
a conventional induction motor."
Mars
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Is 700' the well depth or static level?
There are a lot of 3ph PM motors for VDFs as well. The rotor has magnets (normally rare earth) on its surface or in slots down in the iron. So there are no brushes, no wiring on the rotor. They are more expensive than induction but more power/torque in a unit package size.
VFDs are commonly used to power 3 phase motors from single phase power. 3 phase motors are lighter and cheaper than single phase motors of the same power rating. The problem is 3 phase power is typically not available in residential areas.
Brushless DC motors are actually small 3 phase motor combined with a DC to 3 phase power converter.
Is the "DC to 3 phase power converter" essentially the same as a VFD where the supply DC is chopped up according to some input signal, presumably a DC level or PWM signal? I guess this is what the 'ESC' does on a drone i.e. powering the propeller.
Ampster
Renewable Energy Hobbyist
I think they are similar. I have a brushless DC motor in an ebike that runs off a fairly simple controller. I also had an expensive Curtiss controller and a 3 phase AC motor in an EV conversion and it was much more complex. I suspect the former was pulsed DC because of the way it knocked when first accelerating versus the smooth torque of the AC motor that must have been true AC instead of pulsed DC. Interestingly the ebike motor had five wires, two of which were plain voltage and the other three were the pulsed voltage. The AC motor only had three wires from the controller to the motor.
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nosys70
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it all depends the number of poles de motor has.
cheap motors can have only 7-8 poles, while good ones can have over twenty.
but YES, en ESC is just a PWM controller running on a 2 phases motor.
Drones motors and ESC usually have 3 wires.
cheap motors can have only 7-8 poles, while good ones can have over twenty.
but YES, en ESC is just a PWM controller running on a 2 phases motor.
Drones motors and ESC usually have 3 wires.
I don't know about drones, but industrial "DC" brushless motors are 3 phase (6 wires connected to 3 sets of windings).
Small fans and disk drive motors are often 2 phase with 6 permanent magnets.
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RCinFLA
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Using a VFD three phase inverter system powered from single phase AC is only advantageous if there is a significant benefit to having a variable speed induction motor. The power conversion from single phase AC to three phase AC is 85-95% efficient. The conversion efficiency is a bit worse if the AC to DC conversion has power factor correction frontend converter.
In U.S. there are no power factor regulations for residential appliances so some inverter based refrig, and air cond just rectify with filter cap to convert single phase AC to DC for the VFD inverter to run on. This does not matter for your utility bill but it does matter if running from an off-grid battery powered system as inverter losses are proportional to current through MOSFET's and transformer windings for battery powered inverter which means greater inverter loss for poorer power factor.
For air cond there is an advantage to having a lower startup surge current but an undersized inverter air cond that runs at full speed compressor ON duty cycle can actually consumes more run power then a regular non-inverter air cond of same BTU rating.
I have an expensive Samsung 28 cu ft inverter based refrig and sorry I bought it. It averages 2850 watts per day (watts, not VA) and has PF between 0.5 and 0.65. My previous 25 cu ft plain old GE refrig averaged 1500 watts per day with PF of 0.92. Samsung has obviously made my model refrig for U.S. market to trim their costs as my refrig PF would not meet EU specs.
Since mini-split air cond's are mostly sold outside of U.S. where it is more likely to have minimum power factor regulation requirements they may have power factor correction frontends included in their single phase AC to DC conversion. Perhaps some folks that have measured one with Kill-A-Watt meter could comment on their power factor.
In U.S. there are no power factor regulations for residential appliances so some inverter based refrig, and air cond just rectify with filter cap to convert single phase AC to DC for the VFD inverter to run on. This does not matter for your utility bill but it does matter if running from an off-grid battery powered system as inverter losses are proportional to current through MOSFET's and transformer windings for battery powered inverter which means greater inverter loss for poorer power factor.
For air cond there is an advantage to having a lower startup surge current but an undersized inverter air cond that runs at full speed compressor ON duty cycle can actually consumes more run power then a regular non-inverter air cond of same BTU rating.
I have an expensive Samsung 28 cu ft inverter based refrig and sorry I bought it. It averages 2850 watts per day (watts, not VA) and has PF between 0.5 and 0.65. My previous 25 cu ft plain old GE refrig averaged 1500 watts per day with PF of 0.92. Samsung has obviously made my model refrig for U.S. market to trim their costs as my refrig PF would not meet EU specs.
Since mini-split air cond's are mostly sold outside of U.S. where it is more likely to have minimum power factor regulation requirements they may have power factor correction frontends included in their single phase AC to DC conversion. Perhaps some folks that have measured one with Kill-A-Watt meter could comment on their power factor.
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Ampster
Renewable Energy Hobbyist
That is useful information that makes me realize why my off grid usage was more than I estimated when I was on the grid. I will have to see what my KillaWatt says. Not much I can do about it now but I am sure glad I increased my pack size.
Trade off between single phase and 3 phase motors are related to size, weight and cost. A 3 phase motor will be smaller, lighter and cheaper than a single phase motor of the same horsepower rating.
That is the reason why higher power machinery is almost exclusively powered with 3 phase motors.
The VFD adds variable speed control which makes gearing last longer and reduces startup current requirements. Plus 3 phase power is almost never available in a residence so if you want to use that heavy duty machinery you bought for a song at auction your choices are a VFD or a rotary phase converter (single phase motor driving a 3 phase generator).
That is the reason why higher power machinery is almost exclusively powered with 3 phase motors.
The VFD adds variable speed control which makes gearing last longer and reduces startup current requirements. Plus 3 phase power is almost never available in a residence so if you want to use that heavy duty machinery you bought for a song at auction your choices are a VFD or a rotary phase converter (single phase motor driving a 3 phase generator).
Ampster
Renewable Energy Hobbyist
I was the CFO for a wholesale lumber dealer and all their saws ran off 3 phase. For some reason the rooftop AC units were single phase but my plan was when they needed replacement to go with three phase units.