BONFIGLIOLI active cube 201, Руководство по эксплуатации

Страница: 238 / 285

238 Operating Instructions ACU 12/16
CAUTION
The resistance of the brake resistor must not be less than the minimum value R
b min
-
10%. The values for R
b min
are listed in chapter 5 "5".
If the calculated resistance R
b
of the brake resistor is between two standard series values, the lower
resistance is to be selected.
 Calculation of On Time OT
Z
b
t
t
ED

OT = On Time
t
b
= Braking time
t
Z
= Cycle time
t
spiel
t
b
Example:
t
b
= 48 s, t
Z
= 120 s
% 40 4 , 0
t
t
ED
Z
b
  
In the case of infrequent short braking operations, typical values of the On Time OT are at 10 %, for
long braking operations (
 120 s) typical values are at 100%. In the case of frequent deceleration
and acceleration operations, it is recommended that the On Time OT be calculated according to the
above formula.
The calculated values for P
b Peak
, R
b
and OT can be used by the resistor manufacturers for
determining the resistor-specific permanent power.
19.5 Motor circuit breaker
In order to protect the motor against excessive heat-up, monitoring mechanisms are required which
will identify potential thermal overloading in due time to prevent the motor from damage. The
thermal condition of a motor can be identified in different ways.
1. Direct monitoring via temperature sensors in the winding (see Chapter 19.5.1 "19.5.1")
 PTC
 KTY
 PT1000
 Thermocontact
2. Indirect monitoring of motor temperature
 Monitoring of motor current using the K- characteristic of an integrated motor circuit breaker
 Thermocontact
 Modeling of motor heat-up by consideration of temperature-relevant factors via a
mathematical model I
2
t
The thermal monitoring method is selected based on the type and operating conditions of the motor.
Generally, any of the available methods is sufficient for reliable motor protection. A combination of
methods from both groups (one from each group) and parallel execution is possible.
19.5.1 Motor circuit breaker
Motor circuit breakers are used for protecting a motor and its supply cable against overheating by
overload. Depending on the overload level, they disconnect the motor from power supply
immediately in the case of a short-circuit or they disconnect the motor if an overload has occurred
for some time.