Boost an Inverter

Thread Starter

Haropas

Joined Aug 16, 2019
41
Hello.
I want to run a universal motor with a battery.
First of all I made some experiments and by adding a full bridge rectifier on 220v ac i could successfully run the motor in approximately 200v DC and I did this because with DC I can control the voltage to the motor more easily. So this is a success and i tested it.
Now I want this idea to be portable.
I took a 12-volt car battery and I connected it to a (250W) small inverter then I connected the output with a full bridge rectifier and I could run the motor in DC. Because the motor is 400 watt I can't just connect the inverter to the motor directly but if I put the full bridge rectifier for some reason the motor works but with only one issue. If I put my hand to the motor I could stop the motor with ease. My question is if I can some way increase the current going to the motor and have more torque. The voltage going to the motor is adjusted from 25 to 200 volt. But i think the current is too low and that's why the motor doesn't have torque.
Is there a way to increase the current ? The full bridge rectifier can handle 35Amps and i want approximately 10 to 12 amps
Thanks in advance
 

crutschow

Joined Mar 14, 2008
27,477
If the motor is 400W then how do you expect it to run with good power from a 250W inverter?
You need at least a 500W inverter.
You can't increase the current from the 250W inverter as that's fixed by its power rating.
 

Papabravo

Joined Feb 24, 2006
16,523
Hello.
I want to run a universal motor with a battery.
First of all I made some experiments and by adding a full bridge rectifier on 220v ac i could successfully run the motor in approximately 200v DC and I did this because with DC I can control the voltage to the motor more easily. So this is a success and i tested it.
Now I want this idea to be portable.
I took a 12-volt car battery and I connected it to a (250W) small inverter then I connected the output with a full bridge rectifier and I could run the motor in DC. Because the motor is 400 watt I can't just connect the inverter to the motor directly but if I put the full bridge rectifier for some reason the motor works but with only one issue. If I put my hand to the motor I could stop the motor with ease. My question is if I can some way increase the current going to the motor and have more torque. The voltage going to the motor is adjusted from 25 to 200 volt. But i think the current is too low and that's why the motor doesn't have torque.
Is there a way to increase the current ? The full bridge rectifier can handle 35Amps and i want approximately 10 to 12 amps
Thanks in advance
Motors don't really care about the voltage applied to them. What runs a motor is current. In any power conversion scheme you come up with the power out will always be be less than the power in. Sometimes it will be much less. Let us take some numbers:
12 Amperes @ 200 Volts is 2400 Watts. Assume the conversion is 80% efficient. The required input power will be 2400 / 0.8 = 3000 Watts. That 3000 Watts from a 12 Volt battery will require 250 amperes. Most SLA automotive batteries can supply that current but not for very long. The connecting wires will need to be on the beefy side for continuous operation. If you can stop the motor with your hand, I can tell you that it is drawing nowhere near 3000 watts (4 HP). something just does not add up here.
 

Thread Starter

Haropas

Joined Aug 16, 2019
41
Motors don't really care about the voltage applied to them. What runs a motor is current. In any power conversion scheme you come up with the power out will always be be less than the power in. Sometimes it will be much less. Let us take some numbers:
12 Amperes @ 200 Volts is 2400 Watts. Assume the conversion is 80% efficient. The required input power will be 2400 / 0.8 = 3000 Watts. That 3000 Watts from a 12 Volt battery will require 250 amperes. Most SLA automotive batteries can supply that current but not for very long. The connecting wires will need to be on the beefy side for continuous operation. If you can stop the motor with your hand, I can tell you that it is drawing nowhere near 3000 watts (4 HP). something just does not add up here.
Yes i see. Actually i connected a 4A-19volt LAPTOP charger to the inverter and the motor had 19volts and 4A. So if i had a charger or a small power supply of 50v-10Amps i think it would work . But i dont know. But the laptop charger worked on the Inverter providing 4A. I dont know why
 

Papabravo

Joined Feb 24, 2006
16,523
Yes i see. Actually i connected a 4A-19volt LAPTOP charger to the inverter and the motor had 19volts and 4A. So if i had a charger or a small power supply of 50v-10Amps i think it would work . But i dont know. But the laptop charger worked on the Inverter providing 4A. I dont know why
I call BS here. You had a charger which provides 4A @ 19VDC to the inverter and you claim the inverter puts out 4A @19VDC which would make it 100% efficient. No way José.
At least that is within the power capability of the inverter.
 
Top