Converting the operating voltage of an Enduro servo motor

[williaty]

I have a pair of Enduro Pro SM645-2P servo motors that run on 240V. It's kind of a PITA to get 240V power to them in my house and I need to add another motor for a new machine anyway so I was looking for 120V motors on ebay. I came across a guy selling a SM645-2P yet claiming it was for 120V. I asked him how this could be and he said that the hardware was designed so one version could be sold anywhere in the world so he just "converts the plug" so it can run on 120V. Now, I have some reservations about this but at the same time I have seen wide input range digital devices before that don't require flipping a switch to go from 120V to 240V. Digging into the manual (https://www.universalsewing.com/images/instructions/SM6452P-i.pdf) I can't find anything about a wide input range. The manual does say that the motor is happy with either the single-phase single-leg 240V the UK has or the two-phase dual-leg 240V the USA has and gives wiring diagrams for both.

 

1) Do you guys think it's at least vaguely reasonable to suspect that one hardware version might be getting sold to both 120V and 240V grids worldwide?

2) Do you guys think it's likely to instantly fry the 240V-labeled motor I already have if I try it on 120V wired the 240V-UK way?

[Garyak]

I am currently running 5 enduro pro 220v at 110v. I’ve had them for a couple years and they are ran daily. I’m ordering 3 more. 30$ for 220v, 125$ for 110. They’re both the same motor. If you look at the schematics for there’s only one schematic for both. Exactly the same. 

[trash treasure]

A most colorful shop, Garyak :~)

[Garyak]

6 hours ago, trash treasure said:

A most colorful shop, Garyak :~)

 Plenty of broken toes in there. 

[williaty]

19 hours ago, Garyak said:

I am currently running 5 enduro pro 220v at 110v. I’ve had them for a couple years and they are ran daily. I’m ordering 3 more. 30$ for 220v, 125$ for 110. They’re both the same motor. If you look at the schematics for there’s only one schematic for both. Exactly the same. 

 

Did you do anything other than stick a 120V plug on them? I tried with mine today and, on 120V, it sounded off and maxed out at Speed 30. Plugging it back in to 240V made it sound normal and would run up to the full Speed 45.

 

The parts list for the SM645 series does list a different circuit board for the 120V and 240V versions.

Edited October 26, 2021 by williaty

[Garyak]

I’m running the SM645B enduro pro 220v. I’ve done nothing but put a 110v plug on the cord. They sound like exactly the same running on 220v as 110v. 110v cannot fry the 220v motor. You’d have to more than 220v to burn it up. There is no noticeable loss in power by running it 110v. I use them daily, I buy and sell them often, and there’s a lot of people out there doing the same. Like I said, directions are in the box. Look at the schematics and parts list. It covers both. Down to the last screw, exactly the same. My water well pump is the same way. 220 ran 110. Just in case, you cannot rum a 110 on 220. They we’re cooking. 

[kgg]

On 10/25/2021 at 8:07 AM, Garyak said:

I am currently running 5 enduro pro 220v at 110v.

The manual the OP listed indicates in it's bill of materials their are two different circuit boards, one for 120v input voltage and one for 240v input voltage.

I suspect the 240v board using 120v will provide 25 percent max power and will never get to rated motor speed.

It's a matter of Ohm's Law, Power in watts  = Voltage X Current or Power in watts = Voltage squared divided by resistance in ohms.

Example:  550 watt motor at 220v will require 2.5 amps if you half the voltage then you either got to either draw more current actually double it or loss power. Since the resistance will remain the same in the motor and circuit (220 v x 220v) / 550 watts the circuit has 88 ohms of resistance which should remain the same. Then if you half the voltage to 110 volts and the resistance remains the same (88 ohms) then the available power in watts would be (110 volts x 110 volts) divided by 88 ohms giving 137.5 watts. So in a nut shell you take a 550 watt motor and turn it into a 137.5 watt motor which is a 75 percent drop in available power.

The main problem isn't whether it will run, at what speed or available torque it could provide but potentially a safety and or insurance issue. In North America electrical equipment has to be safety certified (voltage, current, etc) by either ULC or CSA. If an appliance has a fault that causes a problem like God forbid a fire or electrocution or something else and your insurance determine or claim it was the fault of incorrectly running the motor at a lower voltage or you installing the plug outside what it was rated for or recommended by the manufacturer and certified for, guess what could happen. Probably, No insurance and you could be on the hook for the situation.

Believe me, I am all for saving a buck but for me the potential risks out weights any cost saving benefit when it comes to electrical items being used outside their certification limits. Maybe just me.

kgg

 

 

[fredk]

Don't forget chaps that the UK mains electricity has a different alternating rate than the US mains electricity. UK= 50 hertz and US = 60 hertz. This can affect how some electrical items will run

I know you are going from UK 220/240 to US 120 but when we moved from the US to the UK we used transformers for some electrical items and they ran differently on the UK 50 hertz cycle

[johnnydb]

It will likely run on the 120v in most household current. (110 is industrial voltage). However the amps will be higher because a motor will draw the watts it needs to run. 

So if a motor will use 5amps at 240V it will draw 10 amps at 120V (as stated previously) 

It's possible to have a Gizmo inside the motor that can differentiate between the two voltages and automatically change the coil connections to accommodate the change.  

 

And because I'm an electrician and kinda a stickler for accuracy. 

Residential household power is a single phase of a Delta wired transformer that has been center tapped.  Most phased current is 60 degrees apart but residential is 180 degrees apart. 

In commercial/industrial power you have 110/208 volts or 277/480... because the phases are 60 degrees apart. Residential voltages add normally. In residential they are on the exact same plane...it's that old polar addition you did in high school math class that you have forgotten all about because you figured you would never need this in "real life". 

[Northmount]

On 10/26/2021 at 4:10 AM, Garyak said:

110v cannot fry the 220v motor

Many motors have been damaged due to under voltage.  They run hot, have low power output, run slow, cooling fans not as effective due to running slow, etc.  Depends on your definition of "fry".  As motor winding insulation breaks down due to running hotter than design, internal shorts may occur, and your motor could "fry". 

If you only use the motor on lower than design voltage for a few minutes now and then, like many hobbyists, you may get away with few problems, just slow and weak output.