Line Impedance - Baldor 18H Series Installation & Operating Manual

Section 1
General Information
MN718
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 ground.
Input Power Conditioning
Baldor controls are designed for direct connection to standard 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.
Baldor Series H controls require a minimum line impedance of 3%. Refer to
"Line Impedance" for additional information.
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.
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.
Receiving & Installation 3-5