Ask about the problem of contact voltage regulator series connection

dengjohn0902

Ask about the problem of contact voltage regulator series connection [Copy link]

 

There is a product test that requires a single-phase 380V AC power supply. I only have two AC 0~250V contact voltage regulators (input voltage 220V) and I want to achieve it by connecting them in series. After searching, I found two different opinions:

1. Connect the input ends of the two voltage regulators to 220V AC power and the output ends in series. Experimental results: After power-on, under no-load condition, one voltage regulator without a fuse works normally, while the other voltage regulator with a 2A fuse blows. After replacing the fuse, it still blows. I don't understand what causes it.

2. Connect the input of the first voltage regulator to 220V AC, and the output to the input of the second voltage regulator, and measure the output voltage of the second voltage regulator (this is the majority of solutions found). ----- Experimental results: Adjust the knobs of both voltage regulators to 250V, and measure the output voltage of the second voltage regulator, which is only 280V, which does not reach the sum of the voltages of the two regulators as stated in the solution.

Now I am confused, how should these two voltage regulators be connected to get the 380V voltage I need? Or is it impossible?

UUC

Simple series connection is not feasible, probably because of the capacity and auto-coupling limitations.

qwqwqw2088

Similar to the connection method of the transformer, the second method should be possible in theory.

Is it power limited?

huo_hu

This method does not work because the output and input of the voltage regulator share the same neutral line, and the output end cannot be connected in series.

The second one doesn't work either. The maximum output of the voltage regulator can only be 0~250. The second input does not meet the requirements.

You can use an isolation transformer 220~220V, set the wattage, and add a voltage regulator to solve the problem

The output of the isolation transformer and the output of the voltage regulator are connected in series, and the input is connected to 220V. The output of the voltage regulator can be adjusted between 220~450

dengjohn0902

huo_hu posted on 2024-4-12 16:11 This method does not work, because the output and input of the voltage regulator share the same neutral line, and the output end cannot be connected in series with the second one. The maximum output of the voltage regulator is only...

Thanks for the advice, I'll try it first

maychang

[How do I connect these two voltage regulators to get the 380V voltage I need? Or is it impossible? ]

No matter how the two single-phase voltage regulators are connected, a 380V voltage cannot be obtained because the input and output of the autocoupler voltage regulator have a common terminal and the output cannot be inverted.

Use a fixed double-turn transformer (such as the 1:1 isolation transformer mentioned on the 4th floor) to create a reverse voltage, and then connect it in series with the output of the auto-voltage regulator to get a 380V voltage, but the voltages at both ends of this 380V voltage are not the same relative to the ground, and the phase is also wrong.

H12315

Just reverse the connection, connect 220V AC to the output end, and use the original input end as the output. This is a boost structure, but the knob must be adjusted to the maximum before connecting.

maychang

H12315 posted on 2024-4-15 17:47 Just reverse the connection, connect the 220V AC to the output end, and the original input end to the output. This is a boost structure, but you must adjust the knob before connecting...

You want to output 380V from a winding rated at 220V? Are you afraid that the OP's voltage regulator won't emit smoke?

maychang

H12315 posted on 2024-4-15 17:47 Just reverse the connection, connect the 220V AC to the output end, and the original input end to the output. This is a boost structure, but you must adjust the knob before connecting...

220V/220V isolation transformers are commonly used in electronic laboratories. According to what you said, the number of turns of this transformer should be 1:1. Then why can't the primary be wound once and the secondary be wound once, but the primary and secondary should be wound so many times each?

晒太阳的老男孩

Now I am confused, how should these two voltage regulators be connected to get the 380V voltage I need? Or is it impossible?

dengjohn0902

maychang posted on 2024-4-12 18:26 [How should these two voltage regulators be connected to get the 380V voltage I need? Or is it impossible? ] Two single-phase voltage regulators have no...

Thank you teacher for your guidance!

beyond_笑谈

Simple AC voltage regulators are connected in series. I guess there will be a phase difference, which makes it impossible to add up like DC voltage.

H12315

maychang posted on 2024-4-16 09:46 220V/220V isolation transformers are commonly used in electronic laboratories. According to what you said, the number of turns of this transformer should be 1:1. So why can't the primary be wound with one...

Contact voltage regulators are usually autocoupled, so there is no problem with outputting 380 without high power reverse connection, but it is indeed a very dangerous operation. Do you want to try it yourself and weigh the pros and cons?

maychang

H12315 Published on 2024-6-28 17:54 The contact voltage regulator is generally auto-coupled. It does not require high-power reverse connection to output 380, which is no problem. However, it is indeed a very dangerous operation. Do you want to try...

[Contact voltage regulators are generally self-coupling, and there is no problem with outputting 380 without high-power reverse connection]

The contact voltage regulator is indeed autocoupled. But it is impossible to output 380V AC voltage by connecting two contact voltage regulators in series.

You still don't know how transformers, including auto-variable voltage regulators, work, nor do you know why transformers have so many turns. According to the connection method on your 7th floor, it would be strange if there is no smoke.

H12315

maychang posted on 2024-6-28 18:00 [Contact voltage regulator is generally auto-coupled, and does not require high-power reverse connection to output 380. There is no problem.] The contact voltage regulator is indeed auto-coupled. But you need to use...

I didn't say that two voltage regulators need to be connected in series to output 380V. I said that the output is directly connected to 220V, and 380V can be obtained from the input. This does have the risk of smoke, but there is no problem in getting 380V and carrying load. The 5KVA voltage regulator in my hand actually outputs 380V and does not smoke.

maychang

H12315 posted on 2024-7-2 16:31 I didn't say that two voltage regulators need to be connected in series to output 380V. What I said is that the output is directly connected to 220V, and 380V can be obtained from the input. This does have the risk of smoke...

Your original words on the 7th floor are [just reverse the connection, connect the 220V AC to the output end, and the original input end to the output, so it is a step-up structure], that is, the original 220V AC input end of the voltage regulator is used as the output, and the original adjustable output is connected to the 220V as the input. Set the knob to the original maximum first, and then gradually turn left to reduce (at this time, the voltage at the 220V end gradually increases).

In this way, the voltage on the winding is 380V/220V=1.73 times the rated value. The transformer core is already saturated quite a lot, and the no-load current may reach more than ten times. In a very short time (in seconds), the voltage regulator has a large enough thermal capacity and will not smoke. Try turning on the power for a few minutes? Note that the original 220V end should output 380V, that is, the adjustable end is placed at the original 127V position.

H12315

maychang posted on 2024-7-2 16:54 Your original words on the 7th floor are [just reverse the connection, connect the 220V AC to the output end, and the original input end to the output, so it is a boost structure], also...

It's not even a few minutes. I'll try it for a few hours tomorrow and see how the fever goes.

maychang

H12315 posted on 2024-7-10 18:20 It's not even a few minutes. I'll try a few hours tomorrow to see how the fever goes.

OK!

Please note my sentence on the 16th floor: "The adjustable end is placed at the original 127V position", or you can directly use the AC mode of the multimeter to measure the original 220V end and adjust it to 380V.

maychang

H12315 posted on 2024-7-10 18:20 It's not even a few minutes. I'll try a few hours tomorrow to see how the fever goes.

Your voltage regulator has a capacity of 5kVA, and its thermal capacity is quite large. To see the result quickly, you can use a very small 220V to 12V transformer (with much smaller thermal capacity), connect the primary secondary to your 5kVA voltage regulator, and monitor the primary voltage with a multimeter. Adjust your voltage regulator so that the primary voltage of the transformer reaches 380V. See if it is hot.

H12315

maychang posted on 2024-7-10 19:52 Your voltage regulator has a capacity of 5kVA, and its thermal capacity is quite large. To see the results faster, you can use a very small 220V to 12V transformer (the thermal capacity is very small...

220V to 12V is not a question of heat capacity. Even if the heat capacity is enough, the coil at the other end will definitely break down and burn. I tested using an autotransformer to boost the voltage two years ago, but it only increased to 500V-1000V to charge the power capacitor. 1000V withstand voltage is still enough.