User Manual

Heavy Duty Dynamic Braking

1336-5.65 — March, 2007

Selecting a Chopper Module

and the Maximum Dynamic

Brake Resistance

The following calculations are demonstrated using The International

System of Units (SI).

Gather the following information:

• Power rating from motor nameplate in watts, kilowatts, or horsepower

• Speed rating from motor nameplate in rpm or rps (radians per second)

• Motor inertia and load inertia in kg-m

or lb-ft

• Gear ratio (GR) if a gear is present between the motor and load

• Motor shaft speed, torque, and power profile of the drive application

Figure 2 shows the speed, torque, and power profiles of the drive as a

function of time for a particular cyclic application that is periodic over t

seconds. The desired time to decelerate is known or calculable and is within

the drive performance limits. In Figure 2, the following variables are

defined:

ω(t) = Motor shaft speed in radians per second (rps)

N(t) = Motor shaft speed in Revolutions Per Minute (RPM)

T(t)

= Motor shaft torque in Newton-meters

1.0 lb-ft = 1.355818 N-m

P(t)

= Motor shaft power in watts

1.0 HP = 746 watts

-Pb

= Motor shaft peak regenerative power in watts

ω ✕

Rad

2πN