PM30 Conversion Video - Control Panel

[macardoso]

I got side tracked from the original post, but first off, nice wiring! Looks clean which is not a feat that many do well.

Take care with grounding and bonding. You may also wish to consider a perforated and grounded metal cage around that power supply. Toroidal transformers can be pretty noisy and I wouldn't want that right next to my 5V electronics.

I'm a big fan of connectors at the panel wall. Bit of extra effort to add, but makes dealing with the control panel much easier once installed!

 

[ahazi]

It is usually the large capacitors that get charged through a bridge rectifier from the secondary of the transformer. It easy to validate, just disconnect the secondary as unloaded transformer act as an inductor.

Ariel

 

[AdamDee]

Many years ago on a larger power supply for a very high power (3-4 kilowatt) ham radio amplifier I faced the same problem. I solved it by adding a series resistor to limit the initial inrush current and a relay that shorts the resistor out after the initial high current drops.

Here is a diagram that uses DC relay.
View attachment 317140

I used a 220v AC relay so I did not need the diodes and the capacitor. You can probably use a 25 ohm resistor, use a small metal high wattage (25-50 watt) type resistor. You will get a delay of 2-4 seconds.

16 amp fuse/breaker is way too big for a 900 watt transformer, it is an indication that something is wrong. Toroidal transformers are known to be able to pass high current for a short time.

Ariel

Ariel I've taken you advice and sourced an AC relay and resistor. If I understand your DC relay circuit right right, this is how I would wire up the AC equivalent? Photos attached.

 

[mksj]

Transformers have very high inrush currents went first energized, independent of the output. An inductor once powered is used to smooth the power pulses drawn and helps decrease the THD.

Transformer Inrush Current Protection

Inrush Current Limiting thermistors can be used to protect a transformer at turn on for high inrush current.

www.ametherm.com

Inrush Current » Transformer Inrush Current Protection
A transformer draws inrush current that can exceed saturation current at power up.
The Inrush Current affects the magnetic property of the core.
This happens even if the transformer has no load with its secondary open.
The magnitude of the inrush current depends on the point on the AC wave the transformer is switched on.
If turn-on occurs when the AC voltage wave is at its peak value, there will be no inrush current drawn by the transformer. The magnitude of the current in this case will be at normal no load value.
If at turn-on, the AC wave is going through its zero value, then the current drawn will be very high and exceed the saturation current.

 

[AdamDee]

Ariel I've taken you advice and sourced an AC relay and resistor. If I understand your DC relay circuit right right, this is how I would wire up the AC equivalent? Photos attached.

Ahh Sorry! - I'm realizing my wiringisn't quite right.... I'll take another stab at this when I get home tonight!

 

[AdamDee]

realizing my wirin

Transformers have very high inrush currents went first energized, independent of the output. An inductor once powered is used to smooth the power pulses drawn and helps decrease the THD.

Transformer Inrush Current Protection

Inrush Current Limiting thermistors can be used to protect a transformer at turn on for high inrush current.

www.ametherm.com

Inrush Current » Transformer Inrush Current Protection
A transformer draws inrush current that can exceed saturation current at power up.
The Inrush Current affects the magnetic property of the core.
This happens even if the transformer has no load with its secondary open.
The magnitude of the inrush current depends on the point on the AC wave the transformer is switched on.
If turn-on occurs when the AC voltage wave is at its peak value, there will be no inrush current drawn by the transformer. The magnitude of the current in this case will be at normal no load value.
If at turn-on, the AC wave is going through its zero value, then the current drawn will be very high and exceed the saturation current.

Very Informative!

 

[AdamDee]

Many years ago on a larger power supply for a very high power (3-4 kilowatt) ham radio amplifier I faced the same problem. I solved it by adding a series resistor to limit the initial inrush current and a relay that shorts the resistor out after the initial high current drops.

Here is a diagram that uses DC relay.
View attachment 317140

I used a 220v AC relay so I did not need the diodes and the capacitor. You can probably use a 25 ohm resistor, use a small metal high wattage (25-50 watt) type resistor. You will get a delay of 2-4 seconds.

16 amp fuse/breaker is way too big for a 900 watt transformer, it is an indication that something is wrong. Toroidal transformers are known to be able to pass high current for a short time.

Ariel

Sorry for the mixup.... realized my previous wiring was incorrect.... If I've followed your wiring diagram right, I'd wire it up something like this, no?

 

[ahazi]

Sorry for the mixup.... realized my previous wiring was incorrect.... If I've followed your wiring diagram right, I'd wire it up something like this, no?

Almost...

Pin "0" on the relay should go to "L2 120 VAC"

I assume that the relay that you are getting is N.O. (normally open) with 220 volt ac coil.

You will also get a reassuring delayed click with the relay.

Ariel

 

[ahazi]

Transformers have very high inrush currents went first energized, independent of the output. An inductor once powered is used to smooth the power pulses drawn and helps decrease the THD.

Transformer Inrush Current Protection

Inrush Current Limiting thermistors can be used to protect a transformer at turn on for high inrush current.

www.ametherm.com

Inrush Current » Transformer Inrush Current Protection
A transformer draws inrush current that can exceed saturation current at power up.
The Inrush Current affects the magnetic property of the core.
This happens even if the transformer has no load with its secondary open.
The magnitude of the inrush current depends on the point on the AC wave the transformer is switched on.
If turn-on occurs when the AC voltage wave is at its peak value, there will be no inrush current drawn by the transformer. The magnitude of the current in this case will be at normal no load value.
If at turn-on, the AC wave is going through its zero value, then the current drawn will be very high and exceed the saturation current.

This is 100% correct and especially true with big toroidal transformers. I just prsonally don't like thermistors and varistors.

 

[AdamDee]

Almost...

Pin "0" on the relay should go to "L2 120 VAC"

I assume that the relay that you are getting is N.O. (normally open) with 220 volt ac coil.

You will also get a reassuring delayed click with the relay.

Ariel

Like this? I've also added in the primary coil fuses...

Edit: Yes, it is N.O. 220VAC relay