The VFD continuous current shall be higher than the motors’ current at maximum load. Because the VFD itself has all the protection you require for your motor so the only item you are protecting is the Rectifier and DC bus. They are a 5-hp, 230V, 1Ø motor and a 3-hp, 230V, 1Ø motor. Sec. Next, it is important to use the FLA (full load amps) of the motor to finalize the VFD size. Why?
The CEC states that motor conductors must be rated for 125% of the motor FLA. What happens when a VFD is controlling the motor? VFD Cable Selection Guide Motor Properties: AWG Size Selection Chart per NEC NEC Allowable Conductor Ampacity Regulatory Codes Drive HP 230V 3ø AWG 460V 3ø AWG 575V 3ø AWG ½ - 3 14 14 14 5 14 14 14 7 ½ 10 14 14 10 8 14 14 15 6 10 12 20 4 8 10 25 2 6 8 ), cuts your operating costs and increases your mine production by allowing your mining, haulage, and conveying systems to work at their most efficient rates. In VFD Sizing, the main considerations are: 1.
Therefore, it is good practice to size the breaker at 15 Amps. OCPD size = 100% of noncontinuous load + 125% of continuous load.
How do I size the conductors from the VFD to the motor? (a) 30A breaker (b) 40A breaker (c) 50A breaker (d) 80A breaker. What let a VFD feeder breaker trips when turn it off? It does not mention the branch circuit protection. The breaker must be sized for 7.6 * 1.25 = 10 Amps. Variable frequency drives should be protected by fuses. The sizing of the equipment is straightforward. Breaker size must be rated for a minimum of 125% of the full-load current of the motor it is protecting, rounded up to the next standard breaker size.
384-16(c) has the same requirement, except that it's stated in terms of the loading of the OCPD. It is not necessary to size the VFD to the motor FLA rating if the motor application is oversized. If I size the switchboard breaker to match the conductor size as computed by 430-22(a)(exc 2), the motor will not start in the bypass mode. For example, the full-load current of a 5 HP motor at 460V is 7.6 Amps. Let's illustrate this with a sample motor feeder protection calculation. VFDs are chosen by voltage, phase, and horsepower (HP). Friday, December 9, 2016. Refer to Figure 7-13. input current: Continuous (at 400 V )304 [A] o Answer: (d) 80A breaker. It is called derating when doubling the size of the VFD in order to convert the single phase input power to three phase output. What size feeder protection (inverse-time breaker) do you need for the following two motors?
Horsepower An oversized VFD can be used for a smaller HP motor. The UFB-17 feeder-breaker, designed for seam heights between 1,145 to 1,625 mm (48 to 64 in.