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APEX615n Installation Guide
Internal Switching Noise
This noise directly relates to the high dv/dt from the internal switching of the IGBT power
block of the APEX615n's drive. This high dv/dt creates a large earth ground di/dt through the
motor case. This may cause the ground to jump if a solid earth connection is not present.
Depending on how the drive and other equipment are connected to the earth ground, users may
experience voltage spikes on I/O lines. Systems involving data acquisition from low level
analog and digital signals are most vulnerable.
The best method to limit the dv/dt is to add a filter between the drive output and the motor.
This reduces the dv/dt and decreases the di/dt a great deal. These filters have been installed by
Compumotor in several applications with good results. Another method that can be used to
reduce noise is to install AC line input filters. Compumotor has found from our own testing
that properly installed AC line filters, on the drive as well as the controller, reduce noise on
both analog and digital inputs and outputs.
Compumotor has located a series of suitable AC line filters and motor output filters that can
be purchased for use in applications as needed. These filters are manufactured by the
SCHAFFNER Co. and may be purchased by contacting the manufacturer or the stocking
distributor listed at the end of this appendix. The suitable motor output filters are listed
below. The suggested AC line filters are listed in the "Filtering the AC mains supply"
section of Appendix E of this document.
Manufacturer
Part Number
A P E X 6 1 5 1
Schaffner Co.
FN 510-8/29
A P E X 6 1 5 2
Schaffner Co.
FN 510-8/29
A P E X 6 1 5 4
Schaffner Co.
FN 510-16/29
Externally Conducted Noise
Externally-conducted noise is similar to power line noise, but the disturbances are created on
signal and ground wires that are connected to the APEX615n. This kind of noise can get into
logic circuit ground or into the processor power supply and scramble the program. The
problem here is that control equipment often shares a common DC ground wire that may be
connected to several devices, such as a DC power supply, programmable controller, remote
switches, etc. When a noisy device such as a relay or solenoid is attached to the DC ground, it
may cause disturbances within the APEX615n.
To solve a noise problem caused by DC mechanical relays and solenoids, you can connect a
diode backwards across the coil to clamp the induced voltage kick that the coil will produce.
The diode should be rated at 4 times the coil voltage and 10 times the coil current. Using
solid state relays is another way to eliminate this problem.
Diode
DC
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