Dear experts,

I'd like to know how the dynamic braking function work in the new version CU240B...

In the old version the parameter 1237 allowed us to choose the duty cycle for dynamic chopper close to dissipated energy, base on the value of p1237 (% duty cycle), we can choose the suitable Braking resistor which will be connected with the inverter by terminal R1-R2.

But in the new version, the p1237 is not available, and how can I set duty cycle for selecting the braking resistor ?

or I have to choosse the maximum power by using the formular : 

R_braking resistor  = (vdc_max)2  x cosphi / P_motor

P_braking resistor = (vdc_max)2 / R_braking resistor

Ex: Motor power = 45kW , cosphi = 0.9 , 380-400VAC

So the VDC max = 800VDC

R_braking resistor = 800x800 x 0.9 / 45000 = 12.8 ohm 

P_braking resistor = 800 x 800 / 12.8 = 50 kW

in old version we can select the braking power average = 5%, 10%,20% of braking power max

If i choose 10% so i need the braking resistor = 5kW - 12.8 ohM

in new version, what is the exact value should i choose ?

Please help me understanding this issue .

Thanks

Hi TechTeam,

Thank for your infimation,

But the P219 parameter is use to declare the power of braking resistor. The difficulty is :

How to define the best value of Braking resistor correspond with the dynamic braking function of Inverter 2nd generation? Because if we choose a small power of braking resistor, it will be overheat?

Thank you

Hi All,

Does everyone can help me to clear that issue ?

thank in advanced

hello,

I am not expert, but I wonder.

you didn't tell us selected motor and VFD data.

Please do it, because this helps us to get an overall picture of used by you equipments.

Cheers

P.S. And one more. Which kind of load, it is assumed on shaft?

Kanuzac

But the P219 parameter is use to declare the power of braking resistor.

 yes, considering entered value of max braking power that the resistor can handle, the VFD as though extends ramp deceleration time in a bid not to get resistor broken.

So, based on youre comprehensive information I would preffer following things:

• Power module power is equal 55 kWt;
• braking resistor as example JJY:023434020001 (2,75/55 kWt  constant/peak power; R=10Ω).

In extremely hard case of dynamic loading when you need very short deceleration ramp and that deceleration occurs very often, and braking resistor temperature control repeatedly issues "brake resistror temperature is high!", you will have to purchase three the same additional resistors in order to encrease constant power of braking part of VFD.

Cheers

Msorich

 yes, considering entered value of max braking power that the resistor can handle, the VFD as though extends ramp deceleration time in a bid not to get resistor broken.

 When the dynamic breaking is properly commissioned the VDC_MAX controller is disabled so the drive will not extend the decceleration ramp.

m_zlotek

When the dynamic breaking is properly commissioned the VDC_MAX controller is disabled so the drive will not extend the decceleration ramp.

 When the dynamic breaking is properly tuned/commissioned:

• There is no need of disabling the VDC_MAX controller. It's not reasonable to have safety option disabled, at least;
  
• The needed ramp is executed with no fails even when it's used various dynamic load.

Cheers

Msorich

 

m_zlotek

When the dynamic breaking is properly commissioned the VDC_MAX controller is disabled so the drive will not extend the decceleration ramp.

 When the dynamic breaking is properly tuned/commissioned:

• There is no need of disabling the VDC_MAX controller. It's not reasonable to have safety option disabled, at least;
  
• The needed ramp is executed with no fails even when it's used various dynamic load.

Cheers

Actually no, with VDC_MAX turned on, the breaking chopper will never activate as VDC_MAX controller will try to extend the ramp before allowing DC link voltage to rise.

Also, if you read the manual, setting p0219 (breaking power of the resistor) to anything but 0 deactivates VDC_MAX controller.