Voltage Regulator Question

[richardm6994]

Does a voltage regulator have to be under load to work?

 

I've bought one off eBay and connected 240vac to it as shown. But instead of connecting it straight to the motor, I measured the voltage coming from the output terminals without them being connected to anything (other than the multimeter)......and it measured a randomly fluctuating output voltage from around 260 to 280vac, however twisting the 'knob' in any direction made no difference to changing the output voltage.

 

I then read in the item description "Voltage regulation: AC 50-220V APPROX DIFFERENT LOADS AND CONDITIONS EFFECT RESULTS"

and this got me wondering if the regulator has to be under load to work.......and this is why my multimeter reading were all over the place and the knob wasn't doing anything??

 

 

 

 

[IanS]

Looking at the size this is phase control.

The black bit on the heat sink will be a thyristor.

These are either on or off.

It works by switching on part way through the mains 50Hz cycle and switching off when the current drops to zero just before it reverses for the second part of the cycle.

The control is that it switches on nearly at the start of the cycle for full power and nearly at the end of the cycle for minimum power.

So unless your meter is syncronised to the mains (very unusual) or a true RMS meter it will take spot readings all over the cycle and read jumping all over the place.

A tungsten light bulb of 60W or above will act as a good testing load.

 

Have fun

[richardm6994]

Thanks Ian, If I was to connected a full bridge rectifier onto the outputs of this voltage regulator, would I be able to vary the DC voltage that comes out of the rectifier by twisting the knob on the regulator?

Edited April 19, 2016 by steamer

[IanS]

Qualified yes.

You would still need some sort of load and without a resevoir capacitor the DC would be a bit lumpy.

So ordianry light bulb as a load and a 0.1 to 10uF 350V capacitor should work.

[richardm6994]

Thanks Ian. Glad I'm not barking up the wrong tree!!

 

My plan is to attached 110vac onto the voltage reg (and use the knob to adjust output voltage hopefully between 50 and 100vac output voltage).

 

I'm going to connect the full bridge rectifier onto the voltage reg output, and hopefully be able to twist the knob on the regulator to produce a variable DC voltage of between 50 and 100v on the rectifier outputs.

 

I have bought a 4700uf 100v smoothing capacitor for the rectifier.

 

The variable DC voltage from the rectifier outputs is then used to drive a 480w / 100v / 4.8amp DC motor (table powerfeed on milling machine as original electronic controls are bust but the motors run fine).

Edited April 19, 2016 by steamer

[IanS]

Should work.

You might find that full volts are a bit higher than 110V as the capacitor will try to charge to peak volts at around 150V so be carefull not to over drive the motor.

Mark a MAX on the knob

[Guest 2b cruising]

For safety I would try fitting some kind of stop to the knob.

Even if it was just a self tapper coming against a peg.

[sj-bradley]

Those things I have seen are triac based.

 

If you search for bigclivedotcom on youtube, you'll see he has done a complete breakdown on how this thing works. Worth watching.

 

Simon.