How is power divided from a wall outlet? Powering multiple motors with PSUs, extension cord

[shouba]

Recently,I've made a project. It involves powering 7 motors from a wall outlet, using switching power supply units. I am a little over-budget on possible output power, but it is very unlikely that all motors will run max power at the same time. Below is the architecture:

EDIT - Sorry folks, typo in my "infographic". Should be 1700W from the PSUs.

My questions are below. I'm a bit of a newbie so please excuse

1) Can the wall outlet, plus a generic extension cord, really transmit up to ~1800W ? Like is it safe, would anything melt, etc. I've only used extension cords for small electronic devices like laptops.

2) The amperage requested by the motors may be in the 30-50 A range in total, but the wall outlet provides 15A. Just to confirm, the PSUs take care of the power conversion to the amps/volts required, right?

3) What will happen when the system requests more than 1800W ? E.g. if all motors are on and at their highest torque requirements.

4) Similar to above, but for an individual PSU with 400W. What happens if both the 288W motors are trying to request their max power, will power be split evenly at 200W per motor? What if one starts 'working hard' first (taking the max 288W), then after a few seconds the other starts requesting as much power as possible, does it get stuck with only 400-288 = 112W ?

EDIT - one more important question:

My motors are using motor drivers with adjustable current settings (so I can control max #s) and overcurrent protection. Can I leverage these current settings to operate at lower power and ensure I generally don't go over e.g. 1700W? example product M542T: (I am using Stepper Motors)

Thanks for any insights, as well feel free to suggest improvements to the setup. It's based mostly on available parts and physical space constraints, but could change. What's fixed is using the wall outlet as a source, and having those particular motors.
Maybe it's a little bit more problematic, thanks.

 

[augkuo]

Recently,I've made a project. It involves powering 7 motors from a wall outlet, using switching power supply units. I am a little over-budget on possible output power, but it is very unlikely that all motors will run max power at the same time. Below is the architecture:

EDIT - Sorry folks, typo in my "infographic". Should be 1700W from the PSUs.

My questions are below. I'm a bit of a newbie so please excuse

1) Can the wall outlet, plus a generic extension cord, really transmit up to ~1800W ? Like is it safe, would anything melt, etc. I've only used extension cords for small electronic devices like laptops.

Yes you can charge your Tesla through the wall plug at 1.8kW/hr and it'll take a long time to recharge the battery. If the outlet was done to code then you have nothing to worry about. If you have an older home or a non-compliant code installation then yes you could start a fire.
For the extension cords, you'll have to make sure that they can handle the power - the thicker the cord, the more power you'll be able to handle - it should say on the cord itself based upon its length and thickness.

2) The amperage requested by the motors may be in the 30-50 A range in total, but the wall outlet provides 15A. Just to confirm, the PSUs take care of the power conversion to the amps/volts required, right?

Yes, the wall outlet is at 120V/15A so the switching power supplies will convert the voltages and be able to supply more current. They will have some efficiency rating so if it's 90%, if you put in 100W you'll only get 90W.

3) What will happen when the system requests more than 1800W ? E.g. if all motors are on and at their highest torque requirements.

If the system requests more than 1800W but you can't deliver it, then you won't get more than 1800W. So basically the motors will max out at some point but not at the highest torque.

4) Similar to above, but for an individual PSU with 400W. What happens if both the 288W motors are trying to request their max power, will power be split evenly at 200W per motor? What if one starts 'working hard' first (taking the max 288W), then after a few seconds the other starts requesting as much power as possible, does it get stuck with only 400-288 = 112W ?

You can think of your motors as resistors in parallel - so the power will be split among them depending upon their impedances. If both are at max power, then yes the power will be split evenly. If one motor starts at max power and the second starts turning on, then power to the first will decrease and power to the second increases if the power of both is above 400W.

EDIT - one more important question:

My motors are using motor drivers with adjustable current settings (so I can control max #s) and overcurrent protection. Can I leverage these current settings to operate at lower power and ensure I generally don't go over e.g. 1700W? example product M542T: (I am using Stepper Motors)

Thanks for any insights, as well feel free to suggest improvements to the setup. It's based mostly on available parts and physical space constraints, but could change. What's fixed is using the wall outlet as a source, and having those particular motors.
Maybe it's a little bit more problematic, thanks.

 

[Jason S]

I don't think the OP was asking about Tesla charging at all.

Regarding the power issue above, I think you are capped by the actual draw of the motors at any given point in time. If all of the motors attempt to draw max power at the same time, it just won't work. They'll all get partial and it looks like PSU2 & PSU3 are the most oversubscribed.

Oh, and that's all dependent on how much loss you get via the extension cord. Make sure it is a very high gauge extension cord to reduce losses there and reduce possibility of overheating the extension cord.

 

[shouba]

So cool, I'm sure it will be very useful to me, thanks for your help.

 

[shouba]

Thanks.

 

[shouba]

I don't think the OP was asking about Tesla charging at all.

Regarding the power issue above, I think you are capped by the actual draw of the motors at any given point in time. If all of the motors attempt to draw max power at the same time, it just won't work. They'll all get partial and it looks like PSU2 & PSU3 are the most oversubscribed.

Oh, and that's all dependent on how much loss you get via the extension cord. Make sure it is a very high gauge extension cord to reduce losses there and reduce possibility of overheating the extension cord.

Thanks for your help.

 

[mongo]

Recently,I've made a project. It involves powering 7 motors from a wall outlet, using switching power supply units. I am a little over-budget on possible output power, but it is very unlikely that all motors will run max power at the same time. Below is the architecture:

EDIT - Sorry folks, typo in my "infographic". Should be 1700W from the PSUs.

My questions are below. I'm a bit of a newbie so please excuse

1) Can the wall outlet, plus a generic extension cord, really transmit up to ~1800W ? Like is it safe, would anything melt, etc. I've only used extension cords for small electronic devices like laptops.

2) The amperage requested by the motors may be in the 30-50 A range in total, but the wall outlet provides 15A. Just to confirm, the PSUs take care of the power conversion to the amps/volts required, right?

3) What will happen when the system requests more than 1800W ? E.g. if all motors are on and at their highest torque requirements.

4) Similar to above, but for an individual PSU with 400W. What happens if both the 288W motors are trying to request their max power, will power be split evenly at 200W per motor? What if one starts 'working hard' first (taking the max 288W), then after a few seconds the other starts requesting as much power as possible, does it get stuck with only 400-288 = 112W ?

EDIT - one more important question:

My motors are using motor drivers with adjustable current settings (so I can control max #s) and overcurrent protection. Can I leverage these current settings to operate at lower power and ensure I generally don't go over e.g. 1700W? example product M542T: (I am using Stepper Motors)

Thanks for any insights, as well feel free to suggest improvements to the setup. It's based mostly on available parts and physical space constraints, but could change. What's fixed is using the wall outlet as a source, and having those particular motors.
Maybe it's a little bit more problematic, thanks.

Hi,

Out of order:
3) and 4)
You might try thinking in reverse from motor to outlet.
In an operating state, each motor draws some power level.
There is no sharing between the motors, they see the voltage and try to pull their current. Supply tried to maintain voltage and sees the total draw of all connected motors. If the combination of motors on a supply exceeds it's rating/ actual max, it will either brownout (voltage drop), or shut off due to over current (also delayed shut off due to heat).

If the actual draw of the power supplies (motor load/efficiency) exceed the circuit breaker, it will trip.

1) 15 amp outlet is rating 15 amp intermittent 12A/80% continuous. Voltage should not drop appreciably (<3%) over that range.

2) Yes, switching converters work in terms of power and efficiency v.s. linear where current in = current out (mostly)

Didn't look at datasheet, but using the current limit on the motor driver should lower peak load and reduce system power requirements. Make sure you aren't supplying more current than the motors can handle.

P.S. speaking of stepper motors: have you seen the Purdue video of the 007 theme performed on floppy drives?