9 | Connection
STOBER
76
05/2019 | ID 442790.01
ATTENTION!
Damage due to overload!
In order to ensure an even distribution of charging current on all AC-supplied drive controllers, all circuit breakers must be
closed when engaging the power supply.
▪
In order that the input rectifier is not overloaded in the event of a possible fuse failure in the group, evaluation of the
grid monitoring for AC-supplied drive controllers must lead to deactivation of the entire DC link group.
9.3.3
Grid connection in case of parallel connection
All drive controllers must be connected to the power grid simultaneously. Simultaneously in this case means that the time
difference may be a maximum of 20 ms. This condition is generally met if you use contactors of identical design from one
manufacturer.
Provided that simultaneous connection to the grid is achieved, the design with one contactor per drive controller is also
permitted.
ATTENTION!
Damage due to overload!
If the grid does not connect to all drive controllers simultaneously in the design with one contactor per drive controller,
their charging resistors can be damaged.
9.3.4
Residual current protective device
STOBER devices can be protected with a residual current protective device (RCD) to detect residual currents. Residual
current protective devices prevent electrical accidents, especially ground fault through the body. They are generally
classified by their triggering limit and suitability for detecting different types of residual currents.
Depending on the function, leakage currents may occur when operating drive controllers. Leakage currents are interpreted
as residual currents by residual current protective devices and may therefore lead to false triggering. Depending on the
relevant power supply connections, residual currents may occur with or without a DC current component. Because of this,
you should take into consideration both the magnitude as well as the profile of the possible leakage or residual current
when selecting a suitable RCD.
DANGER!
Electrical voltage! Risk of fatal injury due to electric shock!
Leakage currents with a DC current component may occur in 3-phase installations.
▪
Always protect 3-phase installations with type B residual current protective devices, sensitive to all currents.
False triggering – Causes
Depending on stray capacitances and imbalances, leakage currents above 30 mA may occur during operation. Undesirable
false triggering occurs under the following conditions:
§
When connecting installations to the supply voltage. This false triggering can be rectified by using short-time delayed
(super-resistant), selective (delayed switch-off) RCDs or RCDs with increased trigger current (e.g. 300 or 500 mA).
§
Due to higher frequency leakage currents for long motor cables under normal operating conditions. This false triggering
can be rectified for example using low-capacitance cables or an output choke.
§
Due to imbalances in the supply grid. This false triggering can be rectified, e.g. using an isolating transformer.
