# full bridge rectifier into an inverter

#### Haropas

Joined Aug 16, 2019
41
hello.
i want to produce with some way aproximate 220-310 volt dc for a motor .
can i connect to a 12 volt battery a small inverter (250W) and then from the outbut of the inverter connect a full bridge rectifier (KBPC3510) and then a capacitor( 450V-330μF) in order to make 12v dc to 220 AC and then dc again or the inverter will blow up because the diodes from the bridge will make the inverter to malfunction?

if there is an other way and not very expensive please tell me

#### KeithWalker

Joined Jul 10, 2017
1,386
That should work but the output voltage will probably not be 220Vdc. The value will depend on the AC wave shape from the inverter and will be approximately the peak voltage rather than RMS. Make sure the inverter can handle the initial charge current of the smoothing capacitor and the motor starting current, which can be quite a lot higher than the running current.

#### LesJones

Joined Jan 8, 2017
2,836
If you are prepared to hack into a modern design inverter then there will already be a high DC voltage available (Probably about 300 volts.) This is because they first use an inverter running at much higher frequency than the mains supply. This allows a smaller and cheaper transformer to be use to step up the voltage. The high frequency high voltage from the transformer is rectified to produce the high voltage DC. The switching to produce the AC output is done at the high DC voltage level to produce some waveform that is close enough to a sine wave. This can vary from a stepped square wave to a good approximation of a sine wave. You would need to understand what you were doing to use this method.

Les.

#### Tonyr1084

Joined Sep 24, 2015
5,491
What kind of motor? You might not need DC to run a motor of that high a voltage. If it's a universal motor then it will run on either AC or DC. And this is important, how much current will the motor draw and what is it going to be running?

#### Haropas

Joined Aug 16, 2019
41
That should work but the output voltage will probably not be 220Vdc. The value will depend on the AC wave shape from the inverter and will be approximately the peak voltage rather than RMS. Make sure the inverter can handle the initial charge current of the smoothing capacitor and the motor starting current, which can be quite a lot higher than the running current.
If you are prepared to hack into a modern design inverter then there will already be a high DC voltage available (Probably about 300 volts.) This is because they first use an inverter running at much higher frequency than the mains supply. This allows a smaller and cheaper transformer to be use to step up the voltage. The high frequency high voltage from the transformer is rectified to produce the high voltage DC. The switching to produce the AC output is done at the high DC voltage level to produce some waveform that is close enough to a sine wave. This can vary from a stepped square wave to a good approximation of a sine wave. You would need to understand what you were doing to use this method.

Les.
Ok i want to run a universal motor and because i cant regulate the speed if i run it in ac. I mean that this motor can run DC and also AC. But in AC you can't regulate the torque and speed just by regulating the voltage on the motor. If I put 220 volt AC the motor will turn 11000rpm high torque. If I put 100 volt the RPMs remain the same but the torque reduces making the motor not working properly. I managed to run this motor in DC and be much more reliable. I used 72 volt DC battery but because it's expensive I can't have big capacity. So if I can use the inverter and two12 volt batteries it would work. Also I can't find a step up converter turning 12 volts into 220 DC
I don't know exactly how to hack into the inverter and find from where the inverter can produce high voltage DC so if is this possible I would like to try it

#### Tonyr1084

Joined Sep 24, 2015
5,491
Hacking the high voltage of an inverter is dangerous. And that's if you KNOW what you're doing. If you DON'T know - DON'T try. As for rectifying AC into DC - you'll (likely) need a full wave bridge rectifier. Now, for how you're controlling that final voltage - that in itself can present other problems. Since you're not telling us - we can't guess.

Again, what is your end goal? What is the motor running?

#### Dodgydave

Joined Jun 22, 2012
9,837
Could you not use a dimmer type speed control like this..

#### LesJones

Joined Jan 8, 2017
2,836
The solution is easy when we are given the FULL story.

#### Tonyr1084

Joined Sep 24, 2015
5,491
Are you running a generator?

#### Haropas

Joined Aug 16, 2019
41
Are you running a generator?
No i want to run a universal motor and to be exact i want to run a washing machine motor. I actually managed to make this work with the bridge rectifier today, so the real question here is if i can produce 220 volt DC or more with an Inverter

#### Tonyr1084

Joined Sep 24, 2015
5,491
If you have an inverter that produces 220VAC you can rectify that into DC. If you add filtering capacitors then you have to factor in the √2 multiple (1.414 x 220) for the peak voltage. However, running a motor - you wouldn't need to filter. Not unless it was causing undue electrical noise. Just be sure your full wave BR can handle the voltage and the current. Otherwise you could be headed for some excitement.

#### Tonyr1084

Joined Sep 24, 2015
5,491
https://www.amazon.com/Pieces-Chanzon-KBPC3510-Rectifier-Electronic/dp/B079KD2BTT/ref=sr_1_1_sspa

Just be sure to use a good heat sink and thermal paste. Not sure how much power your motor will draw, but at 220VAC, probably less than 10A. But I don't know that for sure. 35A gives you plenty of head room.

Now - Amazon! Who knows how close to those specs that BR actually is. I did a quick search and found that. But you probably would want to buy from a reputable source. Will cost more but you're buying peace of mind.