Brake Resistor; Selection Of The Brake Resistor - Eurotherm 637+/D6R KD6R Product Manual

Electrical installation
5.8

Brake resistor

5.8.1 Selection of the brake resistor

The energy of a moving system flows back to the Drive. The DC-Bus capacitors are able to take a
small value. The rest has to be converted to heat by a resistor.
Switching of this brake resistor depends on the DC-Bus voltage.
The load of the resistor is simulated and supervised electronically (EASYRIDER
Software). Peak power (Pmax) and continuous power (Pd) ratings have to be sufficient to meet the
requirements of the application.
Movement
RPM
n1
T
I [A]
Ib
Braking-Current
Calculation
Step 1
Calculation of brake-power
(Approximation. Capacitor-load, friction-and
drive-losses neglected)
Power of motion:
Pkin = 0,0055 * J * n1² / tb1 [W]
Motor-losses:
Pvmot = Ib² * (Ri + RL) [W]
Cont. Power:
Pd = 0,9 * (Pkin-Pvmot) * tb1 / T
[W]
Peak-Power:
Pmax = (1,8 * Pkin) - Pvmot [W]
used units:
J total inertia [kgm²]
n1 speed at Brake-Start [RPM]
tb1 braking time [Sec]
T cykle time [Sec]
Ib brake-current [A]
Rph resistance of motor (between terminals)
RL line resistance of motor cable [ Ω ]
tb1
t [sec]
t [sec]
Ω ]
[
Product-manual Model: 637+/D6R KD6R
Definition of Data Values for Example
Speed at Brake-Start n1 = 3000 RPM
tb1 = 0,1 sec.
Braking Time
T = 2,0 sec.
Cycle-Time
Total Inertia J = 0,0005 kgm²
Braking-Current Ib = 3,2 A
Motor-Resistance
Rph = 3,6 Ohm
Cable-Resistance
RL = 0,3 Ohm
example
Pkin = 0,0055 * 0,0005 * 3000²/0,1
Pkin = 247 W
Pvmot = 3,2² * (3,6 + 0,3)
Pvmot = 40 W
Pd = 0,9 * (247 - 40) * 0,1 / 2
Pd = 9,3 W
Pmax = (1,8 * 247) - 40
Pmax = 405 W
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