rotation should always be checked prior to connecting the driven equipment. If the motor is rotating
in the wrong direction, reverse any two of the AC motor leads to change the rotation of the motor. Do
not change the motor direction via the VFD’s software parameters. Although changing the VFD’s
parameters can change the motor rotation, if the parameters are reset to the factory defaults, the
motor will then rotate in the opposite direction.
What will happen if the incoming AC line voltage is wired to the VFD’s output terminals?
Applying the incoming AC line voltage to the VFD’s output terminals (T1, T2, and T3) will cause
severe damage to the VFD’s output power components, and will void the warranty.
Does the VFD require any type of circuit breaker or input fuse protection?
Yes. Branch circuit protection via a circuit breaker or disconnect switch and fuses must be provided
to comply with the National Electric Code (NEC) and all local codes. Consult Article 430, Section H, of
the NEC handbook for more information.
What size circuit breaker or input fuses should be used to protect the VFD ?
Select a magnetic circuit breaker or fuse rated at 1.5 times the input current rating of the VFD. For
the Micro Series, SM and SM-Plus Series, the minimum fuse size should be 10 amps, regardless of
the input current. The 10 amp minimum is required to accommodate the inrush during power up. The
VFD provides motor protection.
Bussmann current limiting type fuses with low I 2 T values, rated 200,000 AIC are recommended.
Similar fuses with equivalent ratings by other manufacturers may also be acceptable.
Fuse types are listed below:
• For 240 / 120 Vac and 240 / 200 Vac models, use a KTK-R or JJN type, 250 Vac rated fuse.
• For 480 / 400 Vac models, use a KTK-R or JJS type, 600 Vac rated fuse.
• For 590 / 480 Vac models, use a KTK-R or JJS type, 600 Vac rated fuse.
What is the maximum distance the motor can be from the VFD?
The motor should be located as close to the VFD as possible (100 feet or less). For applications
where the motor is to be located more than 100 feet away from the VFD, a load reactor or dV/dt filter
should be installed. As motor lead length increases, voltage spikes generated by the VFD’s output
transistors become amplified. In extreme cases, these spikes can result in premature insulation
breakdown in the motor. Adding an output reactor or dV/dt filter reduces the spikes.
Most LEESON motors are now using IRIS (inverter rated insulation system). Motors with this feature
allow longer motor leads (200-300 feet) without the use of an output reactor or filter.
What is the input voltage tolerance of the VFDs?
LEESON'S VFDs have input voltage tolerances of +10% and -15%. The VFDs have dual voltage
ratings (e.g. 240 / 200 Vac), and these tolerances apply to both ratings.
• 240 / 120 Vac models: 240 Vac = 204 Vac - 264 Vac; 120 Vac = 102 Vac - 132 Vac.
• 240 / 200 Vac models: 240 Vac = 204 Vac - 264 Vac; 200 Vac = 170 Vac - 220 Vac.
• 480 / 400 Vac models: 480 Vac = 408 Vac - 528 Vac; 400 Vac = 340 Vac - 440 Vac.
• 590 / 480 Vac models: 590 Vac = 502 Vac - 649 Vac; 480 Vac = 408 Vac - 528 Vac.
NOTE: Although the VFDs have dual voltage ratings, not all models have dual current ratings.
Therefore, a larger VFD may be required to meet the motor’s current requirements when operating in
the lower voltage range. Consult the VFD’s installation and operation manual for current ratings.
Page 2 of 6
LEESON Electric Corporation - www.leeson.com
10/15/2009
http://www.leeson.com/TechnicalInformation/faqdrives.html
