I'm familiar with inrush current problems, and inrush limiting, for power transformers. But what about an auto-transformer/autoformer? Do these also have inrush current like a "regular" transformer? I can't quite figure it out. The reason I ask is that I am looking to power some 220V European gear from my US 120V mains. It's a class-D power amp, so peak current draw in use might be high, and so I would need a large auto-transformer and so am concerned that commercial "voltage converters" may need soft start capability. The amp already has it, I am thinking about no-load conditions when I switch on the auto-transformer prior to any other equipment.
Can someone shed some light on this for me, please? Thanks!
Can someone shed some light on this for me, please? Thanks!
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same magnetc field requirements, same inrush current. I have an old tripplite voltage stabilizer that is an autoformer. Huge twang on startup sometimes.
A transformer needs a magnetizing current to function.
This current will flow continuously no load or full load no difference to magnetize the core. It is 90° delayed because of the inductive load.
When the core is not precharged at switch-on this current is double the normal value and for a short time the Xformer gets saturated, because all magnetic particles are magnetized and suddenly the part looses its inductance and a very high current spike flows across the winding only limited by the DC-resistance of the wire and the mains impedance. The transformer will make a humming noise.
This just happens in the first half wave.
This can blow the mains fuse eventually when the Xformer has more than 800VA and since toroids are very low DC-R the spike can be very high.
BTW in Europe we have 230V and UK has 240V mains voltage.
This current will flow continuously no load or full load no difference to magnetize the core. It is 90° delayed because of the inductive load.
When the core is not precharged at switch-on this current is double the normal value and for a short time the Xformer gets saturated, because all magnetic particles are magnetized and suddenly the part looses its inductance and a very high current spike flows across the winding only limited by the DC-resistance of the wire and the mains impedance. The transformer will make a humming noise.
This just happens in the first half wave.
This can blow the mains fuse eventually when the Xformer has more than 800VA and since toroids are very low DC-R the spike can be very high.
BTW in Europe we have 230V and UK has 240V mains voltage.
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Great, thanks for clearing that up for me about inrush.
There are these 2kVA-5kVA voltage converters that you can purchase for step-up/step-down of mains AC. I have only found some of the models up to 1kVA to mention "soft start". I want to use it to convert 120VAC to 230VAC now, and later when I move to Europe I will want to do the reverse to power some US gear that I bring with me. So I would like to find a simple auto-transformer in a case, with a few outlets of each type, since this can easily be used either way. Like this model perhaps:
5000 Watt Diamond Series Voltage Converter
Is this type of unit a good option, or should I look for something different?
There are these 2kVA-5kVA voltage converters that you can purchase for step-up/step-down of mains AC. I have only found some of the models up to 1kVA to mention "soft start". I want to use it to convert 120VAC to 230VAC now, and later when I move to Europe I will want to do the reverse to power some US gear that I bring with me. So I would like to find a simple auto-transformer in a case, with a few outlets of each type, since this can easily be used either way. Like this model perhaps:
5000 Watt Diamond Series Voltage Converter
Is this type of unit a good option, or should I look for something different?