Hello,

I have a need to regulate the 124 VAC coming from the outlet in my lab down to 115-120 VAC.

The reason for this is I have 200-240 VAC motor, and motor driver I need to power. I know the best option is to have a 220 leg installed from the electrical panel of the building. That is something we plan to do in the future. Right now the ideal situation is if I can get a balanced 220 VAC, that can handle or supply the inrush when motor is turned on, from a standard 115-125 VAC american wall outlet.

Currently have a step-up transformer that is built for refrigerators, so it can handle the inrush. The problem is the power from the outlet is 124 VAC so the load side of the transformer is 246 VAC. This is above the 240 voltage the manufacture recommends for the motor and driver.

I appreciate any help or suggestion.

 

I would seek out a variac, which is a trade name for a tapped auto transformer. With such you can adjust the output typically from 0 to 130% of the input.

You may want to get one rated for that 220 volt line you plan to install, as doubling a 124 volt line yeilds 248 V which is also above your motor rating. Running a variac at a lower voltage is OK, do not run them at a higher voltage.

 

Another cheaper method is with a Buck-Boost transformer, this is a small transformer on the output side which can increase or decrease the power by the value of the secondary winding.
In your case you would need a 240v/10 to 12v secondary.
Is the driver that critical? It seems a very tight tolerance for something like a motor driver.
BTW, if your 120v is high, so will the 240v from the panel most likely.
Max.

 

It's not that hard to install a 240V line. If you plan to do it anyway, just do it. Done properly, this is a safer, more efficient, and more reliable solution. Why muck around with the intermediate solution?

 

@Schalk What is the type of AC motor that you are wishing to control and the nature of the controller?
Max.

 

What is the motor current rating?

A cheap way to lower the voltage is to add a 120VAC to 6 Vac transformer at the input.
You connect the 6VAC transformer output in series with the input to the step-down transformer with polarity such as to subtract the 6 VAC from the mains supply (which then should give you about 118 VAC from the 124 VAC mains).
You can experimentally determine the proper polarity by connecting the 6VAC secondary in series with the mains voltage and measure the output between the secondary and the other mains connection.
The incorrect polarity will cause an increase in total voltage and the correct will cause a decrease.

Of course the current rating of the 6Vac transformer must be at least as high as the step-down input current rating.

 

A cheap way to lower the voltage is to add a 120VAC to 6 Vac transformer at the input.
You connect the 6VAC transformer output in series with the input to the step-down transformer with polarity such as to subtract the 6 VAC from the mains supply (which then should give you about 118 VAC from the 124 VAC mains).
You can experimentally determine the proper polarity by connecting the 6VAC secondary in series with the mains voltage and measure the output between the secondary and the other mains connection.
The incorrect polarity will cause an increase in total voltage and the correct will cause a decrease.

.

AKA Buck-Boost Tfmr.
Max.

 

Another cheaper method is with a Buck-Boost transformer, this is a small transformer on the output side which can increase or decrease the power by the value of the secondary winding.
In your case you would need a 240v/10 to 12v secondary.
Is the driver that critical? It seems a very tight tolerance for something like a motor driver.
BTW, if your 120v is high, so will the 240v from the panel most likely.
Max.

The manufacture of the controller (power is feed to controller and controller distributed power to driver and motors) recommended not going over 240 VAC for power into their device. I tested an older unit with our ACUPWR transformer and it powers up fine. Also to note we had zero issues with the older models, but those models are discontinued and the current model is the one that I am having issues with. Also this new transformer gives me European power 246 VAC on one leg in reference to ground and 0 VAC in reference to ground. The older transformer that I have been using is a Square D Isolated transformer that gave me 110 VAC on one leg with reference to ground, and 116 VAC on the other leg with reference to ground. So this power is under the 240VAC thresh hold but it is unbalanced.

So this is what the manufacture recommends to power their controller true 220 VAC, where both legs are balanced in reference to ground. If not I run the risk of damaging the controller over time and have more frequent errors over time.

 

AKA Buck-Boost Tfmr.
Max.

My apologies for not more closely reading your post or I wouldn't have posted mine.

 

So if both legs are referenced to ground you either need a centre tapped transformer or use the N.A. 240v supply?
I have never seen those requirements in all the time of installing motors of all descriptions.
Who is the manuf? And what is the nature of the motor? AC? BLDC etc.
IT seems overly fussy as to specifications for a AC motor controller?
Max.

 

The controller is for a 6 axis robot arm, sorry for being veg but have to limit the information I release without getting NDAs signed.

So power is plugged into the controller and all items for this robot to function receive power needed from this power connection. So the motors, drivers and other circuits get power from this power distribution system.

 

@Schalk What is the type of AC motor that you are wishing to control and the nature of the controller?
Max.

The motors seem to a stepper motor, I am limited on information on these aspects of the robot arm, but will ask manufacture next time I talk to them.

 

Stepper motors for motion control/robotics are generally very low voltage, not any where near 200v.
Motors for robotics's are traditionally servo and are controlled with Absolute encoders, i.e. position is known at power up.
Max.

 

Stepper motors for motion control/robotics are generally very low voltage, not any where near 200v.
Motors for robotics's are traditionally servo and are controlled with Absolute encoders, i.e. position is known at power up.
Max.

Yes, I agree. I was surprise when I took the cover off the robot arm. Again I can not say for certain but have programmed against many servos in past 5 years and these looked like stepper motors with high end encoders on them. So this might have been a cheaper option for the manufacture, not sure.

 

Hello,

I have a need to regulate the 124 VAC coming from the outlet in my lab down to 115-120 VAC.

The reason for this is I have 200-240 VAC motor, and motor driver I need to power. I know the best option is to have a 220 leg installed from the electrical panel of the building. That is something we plan to do in the future. Right now the ideal situation is if I can get a balanced 220 VAC, that can handle or supply the inrush when motor is turned on, from a standard 115-125 VAC american wall outlet.

Currently have a step-up transformer that is built for refrigerators, so it can handle the inrush. The problem is the power from the outlet is 124 VAC so the load side of the transformer is 246 VAC. This is above the 240 voltage the manufacture recommends for the motor and driver.

I appreciate any help or suggestion.

This is not likely to be a new problem. There must be a distributor in your area that has a solution.