Need help choosing the proper AC voltage regulator

Thread Starter

cmartinez

Joined Jan 17, 2007
6,644
I want to buy a voltage regulator, and I know that the market offers:
  • Cheap-o types that are not real regulators, but instead switch between two coils to more or less approximate the desired output voltage, and also include simple filtering circuitry.
  • There are also the "electronic" voltage regulators out there. That I must confess, have not bothered to check how they work (maybe they're the same thing as the coil-switchers)
  • And then there are the true "ferro-resonant" regulators that weight like about a ton, and that I think are really some sort of isolation transformers with more sophisticated circuitry.
Assuming that I want to protect delicate electronic equipment, and that I also want to filter and reject electrical noise and harmonics at its output, which type would be best for my application?
 

crutschow

Joined Mar 14, 2008
23,764
The ferro-resonant regulators work well, if the AC frequency doesn't vary, as from the mains, but won't work for a source that varies some in frequency, like a gas powered (but non-inverter type) generator.

Have you considered an Uninterruptible Power Supply (UPS), if the load isn't too high?
They protect you from any line variations/transients as well as brownouts and power outages.
 

Thread Starter

cmartinez

Joined Jan 17, 2007
6,644
The ferro-resonant regulators work well, if the AC frequency doesn't vary, as from the mains, but won't work for a source that varies some in frequency, like a gas powered (but non-inverter type) generator.

Have you considered an Uninterruptible Power Supply (UPS), if the load isn't too high?
They protect you from any line variations/transients as well as brownouts and power outages.
The regulator is intended for a machine I built that uses a step motor driver (120VAC@6.5A), a computer and LCD monitor, and a small control circuit that I built. It's all powered from mains, and I don't think that the AC frequency varies too much (if maybe nothing at all)
I not only want to protect the equipment, but also want to filter any noise that could reach the optical encoder that I'm using. The encoder is located at about 12ft away from the circuitry, and it's connected using shielded wire.

You make the ferro-resonant option sound like a good plan...
 

#12

Joined Nov 30, 2010
18,167
American power line frequency is very stable. There is a museum display somewhere in the north-east (Philadelphia?) that shows tiny drift rates and compensation applied by the power companies in real time. Tiny errors, like 0.02 Hz.
http://www.leapsecond.com/pages/mains/

The ferro-resonant transformers are pretty good over a +/- 10% range for voltage, but they have nothing (that is better than any ordinary transformer)to suppress noise. So, either suppress the noise yourself, or consider a UPS. You are easily under 1KW. Good availability.
 

Thread Starter

cmartinez

Joined Jan 17, 2007
6,644
American power line frequency is very stable. There is a museum display somewhere in the north-east (Philadelphia?) that shows tiny drift rates and compensation applied by the power companies in real time. Tiny errors, like 0.02 Hz.
http://www.leapsecond.com/pages/mains/

The ferro-resonant transformers are pretty good over a +/- 10% range for voltage, but they have nothing (that is better than any ordinary transformer)to suppress noise. So, either suppress the noise yourself, or consider a UPS. You are easily under 1KW. Good availability.
Yeah, I was thinking about aquiring a 2kW ferro-resonant regulator with the following specs:
  • Input: 127 VAC +10% -25%, Frequency: 60 Hz ± 3Hz, PF: 0.90 minimum at full load and nominal voltage
  • Output: 120 VAC +/-3%
  • Noise rejection: common mode >120 db, transverse mode >60 db
I must confess, I've never heard of "transverse mode rejection" o_O
 

#12

Joined Nov 30, 2010
18,167
That's way better noise rejection than I expected.
Maybe because the ferro-resonant power supplies I worked with was in 1975.
 

Techno Tronix

Joined Jan 10, 2015
139
The ferro-resonant regulators work well, if the AC frequency doesn't vary, as from the mains, but won't work for a source that varies some in frequency, like a gas powered (but non-inverter type) generator.
I agree. Ferroresonant regulators provides good isolation of load equipment from line noise and surges. Even its design can limit the amount of current to the load.
But it has other side also to consider with high overload, it is common that constant voltage transformer be oversize by 2 to 3 times the rated load current.
 

Thread Starter

cmartinez

Joined Jan 17, 2007
6,644
But it has other side also to consider with high overload, it is common that constant voltage transformer be oversize by 2 to 3 times the rated load current.
I always buy things with at least twice the capacity that I calculate will be needed. A 2kVA regulator should be more than enough for what I want.
 

shortbus

Joined Sep 30, 2009
7,236
The regulator is intended for a machine I built that uses a step motor driver (120VAC@6.5A), a computer and LCD monitor, and a small control circuit that I built.
Aren't stepper motors DC? The stepper drives convert the AC to DC in the first stage, as do computers. so why would line frequency (within normal parameters) matter?
 

MaxHeadRoom

Joined Jul 18, 2013
19,414
I have used optical encoders in all kind of noisy industrial environments with no problems, I do insure however to use differential mode of transmission, but all are TTL RS485 output.
There are millions of CNC M.C.'s etc out there that are working this way.;)
Max.
 

crutschow

Joined Mar 14, 2008
23,764
Aren't stepper motors DC? The stepper drives convert the AC to DC in the first stage, as do computers. so why would line frequency (within normal parameters) matter?
The frequency only matters if you are using a ferro-resonant AC line voltage regulator.
 

Thread Starter

cmartinez

Joined Jan 17, 2007
6,644
I have used optical encoders in all kind of noisy industrial environments with no problems, I do insure however to use differential mode of transmission, but all are TTL RS485 output.
There are millions of CNC M.C.'s etc out there that are working this way.;)
Max.
That is extremely valuable info, Max. Thanks.
 

Thread Starter

cmartinez

Joined Jan 17, 2007
6,644
Aren't stepper motors DC? The stepper drives convert the AC to DC in the first stage, as do computers. so why would line frequency (within normal parameters) matter?
To protect the drive's internal power supply, and also the computer's.
And in an industrial application, sometimes power lines can be treacherous and unreliable.

A few years ago I lost a computer and some important info because a jackass had connected a hydraulic pump's motor to the same line that the office's electronic equipment was connected to... During production, that motor stalled and then kicked back, sending back an emp through the power line... up in smoke things went inside...
 

MaxHeadRoom

Joined Jul 18, 2013
19,414
BTW,
I not only want to protect the equipment, but also want to filter any noise that could reach the optical encoder that I'm using. The encoder is located at about 12ft away from the circuitry, and it's connected using shielded wire.
.
BTW, I have used this circuit/IC's to convert if the encoder is single ended.


Max.
 
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