5

Electrical Installation

 

 

5.8Brake resistor

5.8.1Selection 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→ Windows - Software). Peak power (Pmax) and continuous power (Pd) ratings have to be sufficient to meet the requirements of the application.

RPM

Movement

n1

 

I [A]

T

tb1

t [sec]

 

 

 

 

Ib

Braking-Current

 

t [sec]

Definition of Data

Values for Example

 

 

 

Speed at Brake-Start

n1 = 3000 RPM

Braking Time

tb1 = 0,1 sec.

Cycle-Time

T = 2,0 sec.

Total Inertia

J = 0,0005 kgm²

Braking-Current

Ib = 3,2 A

Motor-Resistance

Rph = 3,6 Ohm

Cable-Resistance

RL = 0,3 Ohm

 

 

 

 

Calculation

 

Step 1

example

Calculation of brake-power

 

(Approximation. Capacitor-load, friction-and drive-

 

losses neglected)

 

 

 

Power of motion:

Pkin = 0,0055 * 0,0005 * 3000²/0,1

 

Pkin = 0,0055 * J * n1² / tb1 [W]

Pkin = 247 W

 

 

Motor-losses:

Pvmot = 3,2² * (3,6 + 0,3)

 

Pvmot = Ib² * (Ri + RL) [W]

Pvmot = 40 W

 

 

Cont. Power:

Pd = 0,9 * (247 - 40) * 0,1 / 2

 

Pd = 0,9 * (Pkin-Pvmot) * tb1 / T

Pd = 9,3 W

 

[W]

 

 

 

Peak-Power:

Pmax = (1,8 * 247) - 40

 

Pmax = (1,8 * Pkin) - Pvmot [W]

Pmax = 405 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) [Ω]

 

RL

line resistance of motor cable [Ω]

 

 

 

 

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54

Product Manual Type: 637f

07-02-10-01-E-V0505.doc