Ndrive HL User’s Manual
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Step #3 Suppression and Snubber Requirements
Due to the inductive effects of the brake, suppression and/or snubber, components are
needed to reduce arching and prevent damage to the Brake Relay contacts. Suppression
can also reduce the electrical noise that is emitted when the circuit is switched off.
Following are three suppression circuit examples.
Example #1:
Figure 4-5 is an example of a typical 24 VDC brake circuit. In this
example, the Varistor, is the suppression device, connected across the
brake. This method of suppression is used in circuits operating at
voltages up to 25 VDC and AC circuits operating at voltages up to 18
VAC. If the voltage is greater than 25 VDC or 18 VAC, one of the other
suppression methods should be used.
Example #2:
Figure 4-7 is an example of a suppression circuit that can be used for
systems using a DC supply. In this example, the diode is the suppression
component, which is connected across the brake. It is important that the
diode be installed, so that it is normally reversed biased. This diode must
have a reverse voltage rating greater than the users DC power supply and
a maximum current rating of at least 1 Ampere. Due to the time needed
for this suppression device to dissipate the energy released by the load
inductance there may be a slight delay (less than 1 second) before the
brake responds to its power being switched off. If this delay is
unacceptable, Example #3 should be used.
Figure 4-7.
Diode Suppression for DC Brake Systems
The user may reconfigure the connections for the brake,
such that the positive supply lead is switched by the relay
instead of the supply common.
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