How to rate the pre-fuses?
Basically, two types of fuse are available for the user:
- Fusing according to allocation type „1“ DIN EN 60947-4-2.
After a short circuit, the braking device is allowed to be inoperative. - Fusing according to allocation type „2“ DIN EN 60947-4-2.
After a short circuit, the braking device must be suitable for further use. However, there is the danger that the contacts of the braking relay (braking contactor) weld. Therefore, if possible, these contacts are to be checked prior to reconnecting the device to the supply. If this check cannot be carried out by the user, the device has to be returned to the producer in order to have it checked.
The following dimensioning information refers to the below operating conditions:
- Use of standard asynchronous motors
- Braking time not exceeding 20s, for braking devices up to 36A
- Braking time not exceeding 40s, for braking devices from 40A up
- Braking current not exceeding 2.5x INOM of the motor
- Cyclic duration factor (c.d.f.) not exceeding the value indicated on the data sheet
Fusing according to allocation type „1“:
As pre-fuses, we recommend to use line protection fuses (utilization category gL) or automatic circuit-breakers with tripping characteristic B, C, D or K.
Taking into account the maximum braking currents that occur (normally the nominal/rated device current), we recommend fuses according the information in the respective instruction manual.
Note! Wiring cross-sectional area according to DIN VDE 0100-430, DIN EN 57100-430.
Fusing according to allocation type „2“:
The power semiconductors are to be protected by fuses of the utilization category gR (semiconductors fuses, high-speed fuses).
However, since these fuses do not ensure line protection, it is necessary to use additionally line protection fuses (utilize. Category gL).
As for the dimensioning of the line protection fuse (gL), please refer to the instruction manual.
To protect the semiconductors it is necessary to select gR-fuses featuring cutoff I²t-values of the ranges indicated in technical data sheet or instruction manual.
In this connection, the current value of the selected fuse should not be smaller than the braking current to be expected (nominal/rated device current).
Notes
- On the basis of the recommended I²t-value, braking current, and possibly the c.d.f., the fuse supplier is able to select a suitable type. Due to the great variety of producers, sizes and types, PETER electronic does not recommend any particular fuses.
- If the value of the fuse or cutoff-I²t is selected too small, it may happen that the semiconductor fuse reacts during braking
