User Guide

2-4 Installation MN850
AC Main Circuit
Power Disconnect A power disconnect should be installed between the input power service and the control
for a fail safe method to disconnect power.
Protective Devices Recommended fuse sizes are based on the following:
175% of maximum continuous current for time delay.
300% of maximum continuous current for Fast or Very Fast action.
Note: These general size recommendations do not consider harmonic currents or
ambient temperatures greater than 40°C.
Be sure a suitable input power protection device is installed. Use the recommended
circuit breaker or fuses listed in Table 2-5 (Wire Size and Protection Devices). Input and
output wire size is based on the use of copper conductor wire rated at 75 °C. The table is
specified for NEMA B motors.
Circuit Breaker: 3 phase, thermal magnetic.
Equal to GE type THQ or TEB for 230VAC or
Equal to GE type TED for 460VAC and 575VAC.
Fast Action Fuses: 230VAC, Buss KTN
460VAC, Buss KTS to 600A (KTU for 601 to 1200A)
Very Fast Action: 230VAC, Buss JJN
460VAC, Buss JJS
Time Delay Fuses: 230VAC, Buss FRN
460VAC, Buss FRS to 600A (KLU for 601 to 1200A)