Regenerative braking dc motor controller

[calhau0]

Hi

i'm trying to implement regenerative braking on a simple dc motor controller
i'm aplying a pwm signal to the mosfet to control the motor speed, but i can't figure out how to put the regen part working

i was hoping that when the M1 mosfet is off, that the motor current would flow trought D1 diode but tha doesn't happen

can anyone help me with this?

thanks !

 

[duke37]

Do you mean that the battery has 0V?
The mosfet is connected 'upside down' and will pass current through its internal diode.
D1 is connected so that it will not pass current.

I would not know how to implement regenerative braking. As the motor slows down, the voltage it produces will drop and some circuit will be needed to raise the voltage to recharge the battery, think about boost converter.

How much energy do you have that you wish to recover, the efficiency may not be high enough to bother.

 

[calhau0]

it's a 200v battery, the diode is placed so as it allows the current to pass when the motor is acting as a generator

 

[duke37]

The motor will only act as a generator when it is spinning fast and producing over 200V.
You need some circuitry to raise a low motor voltage to over 200V to recharge the battery.

Trams and trains have used resistive braking because of the problem of getting the energy back into the supply. Now complex circuitry is more reliable and cheap so that regenerative braking is possible, even into AC supplies.

 

[(*steve*)]

For a high side switch like this, you normally use a P channel mosfet. You need t be careful not to exceed the Vgs(max) of the device though.

 

[calhau0]

so i need a dc-dc converter buck boost to raise the generated motor voltage to over 200v ?

 

[calhau0]

to charge a Li-ion 200v battery how higher must the generated voltage be? 210v? 250v?

 

[(*steve*)]

to charge a Li-ion 200v battery how higher must the generated voltage be? 210v? 250v?

200.00000000001V is sufficient.

Depending on how you do it, the voltage will be clamped to the battery voltage plus any I^2R losses.

The higher the open circuit voltage at whatever speed the motor is turning, the greater the potential for dynamic braking.

 

[calhau0]

so you say the higher a set the dc-dc output the greater the stoping power?

 

[calhau0]

will this new sche. work? only added boost converter to the generated motor voltage

 

[duke37]

That is the sort of thing that is necessary.

Use a P channel fet for M3 as 'steve' said.
I do not think you need D3.
A capacitor should be connected across the motor to take account of the high frequency load.