Engineers Edge Dynamic Braking Resistors Calculations - Engineers Edge

 

Dynamic Braking Resistors Calculations

 

Electronic Electrical Devices | Dynamic Braking Resistor Supplier Distributors
Dynamic Braking Resistors About

Current of Dynamic Braking Motor ( Resistors ) based on Power

Where:
Ires = Dynamic resistor current (amps)
Pmotor = Motor power
n = Motor efficiency (.95 to .90) for most large electric motor applications, (.90 - .83) for smaller motors.
800 = Constant

Next calculate the dynamic resistor resistance max (ohms)

Where:
Rmax = Resistance
Ires = Dynamic resistor current (amps) see above

With the Rmax, which is based on the Ires, consult your dynamic braking resistor manufacturer specification for your operating voltage to define your required braking resistor.

Resistor Power Rating

D = Duty cycle, D=1 when resistor is dissipating energy continually.

Power Dissipation:

240 v installation

480 v Installations

600 v installation 

Where: 

Pres = Power dissipation
D = Duty cycle
R = Resistance in ohms

The power dissipation number is between 0 and 1. Typically, D will never be specified less than 0.2. This will ensure that the minimum power rating of the resistor will always be sufficient. The duration of the braking period determines the temperature rise of the resistor as determined by the thermal time constant of the resistor (manufacturer specified).  Typical braking applications are intermittent (D <1),  the resistor should not be designed for continuous operation. Braking resistors are normally sized for the average power dissipation over the braking cycle time. 

Maximum braking power

Where:

Vbrake = Voltage during braking
R = Dynamic Breaking Resistor rating (ohms)

Braking Torque:

Combine equations above and:

Torquebraking is the effective braking torque created by the electric motor.  Torque is in Newton-meters

 

© Copyright 2000 - 2009, by Engineers Edge, LLC All rights reserved.
Disclaimer

 

Home
Engineering Store
Products & Services
Engineering Forum
CAD Forum
Engineering Design Data
Engineering News
Engineering Motion
Engineering Calculators
Newsletter Register
Advertise
Feedback

What's New at Engineers Store? more
13 3/8" Adjustable Male Human Figure Template
13 3/8" Adjustable Male Human Figure Template
$17.98

GD&T Training ASME & ISO
DFM Training
Copyright Notice