System Grounding; Power Disconnect; Protection Devices - Baldor FPX A05T Installation & Operating Manual

System Grounding

Ungrounded Distribution System
With an ungrounded power distribution system it is possible to have a continuous
current path to ground through the MOV devices. To avoid equipment damage, an
isolation transformer with a grounded secondary is recommended. This provides
three phase AC power that is symmetrical with respect to ground.
Input Power Conditioning
Baldor controls are designed for direct connection to standard single and three
phase lines that are electrically symmetrical with respect to ground. Certain power
line conditions must be avoided. An AC line reactor or an isolation transformer
may be required for some power conditions.

Power Disconnect

and the control for a fail--safe method to disconnect power. The control will remain
in a powered-up condition until all input power is removed from the control and the
internal bus voltage is depleted.

Protection Devices

Input and output wire size is based on the use of copper conductor wire rated at
75 #C. Table 3-1 and 3-2 describes the wire size to be used for power connections
and the ratings of the protection devices. Use the recommended circuit breaker or
fuse types as follows:
Recommended fuse sizes are based on the following:
For European installations, you may want to consider the following fast acting
fuse: Gould Shawmut Cat. No. ATMR15 for up to 15 amperes.
3-4 Receiving & Installation
Continued
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If the feeder or branch circuit that provides power to the control has
permanently connected power factor correction capacitors, an input AC
line reactor or an isolation transformer must be connected between the
power factor correction capacitors and the control.
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If the feeder or branch circuit that provides power to the control has
power factor correction capacitors that are switched on line and off line,
the capacitors must not be switched while the control is connected to the
AC power line. If the capacitors are switched on line while the control is
still connected to the AC power line, additional protection is required.
TVSS (Transient Voltage Surge Suppressor) of the proper rating must be
installed between the AC line reactor or an isolation transformer and the
AC input to the control.
A power disconnect should be installed between the input power service
The control must have a suitable input power protection device installed.
Circuit Breaker: 1 phase, thermal magnetic.
Equal to GE type THQ or TEB for 115 or 230 VAC
3 phase, thermal magnetic.
Equal to GE type THQ or TEB for 230 VAC or
GE type TED for 460 VAC.
Time Delay Fuses: Buss FRN on 230 VAC or
Buss FRS on 460 VAC or equivalent.
UL 508C suggests a fuse size of four times the continuous output
current of the control.
Dual element, time delay fuses should be used to avoid nuisance trips
due to inrush current when power is first applied.
MN1276