Soft start or vfd

[deakin]

i no longer have 3ph service and run off of a ph converter. one machine, 10hp - 240v 3ph 1750rpm, starts under a high load. inrush current is 185@ and the 20hp ph converter cannot handle it. (it's running off of a 100@ 1ph sub panel)

soft start. vfd or quit taking in heavy work? i don't have any experience in any of the three.

 

[Ulma Doctor]

what type of converter are you using? Static or RPC ?
soft starter and VFD's could both be utilized

 

[JimDawson]

VFD is the only way to go. At 10HP, you will still need the RPC to generate 3 phase for the VFD. A VFD is much less expensive then a soft star, as well as being very flexible.

I have no problems starting my 10hp spindle off of a 15hp RPC and a VFD.

 

[deakin]

what type of converter are you using? Static or RPC ?
soft starter and VFD's could both be utilized

rpc

 

[deakin]

VFD is the only way to go. At 10HP, you will still need the RPC to generate 3 phase for the VFD. A VFD is much less expensive then a soft star, as well as being very flexible.

I have no problems starting my 10hp spindle off of a 15hp RPC and a VFD.

i'm not starting a spindle tho'

this machine starts under a very heavy load

 

[JimDawson]

i'm not starting a spindle tho'

this machine starts under a very heavy load

I also run my air compressor with a VFD. In that case it is loaded, it is set to ramp up over 10 seconds, the starting current never goes over the max running load.

What kind of machine are you starting?

 

[deakin]

I also run my air compressor with a VFD. In that case it is loaded, it is set to ramp up over 10 seconds, the starting current never goes over the max running load.

What kind of machine are you starting?

think of a big belt sander with 300# sitting on it when starting.

 

[mksj]

Cost of a VFD will be more than a soft start, if you do not need any of the other VFD features. There is some derating of VFD's when run off of RPC's, typically I just add a DC choke which decreases THD/current peaks. I would look at a soft staarter run off the RPC to the motor. WEG makes some reasonable cost ones would need to see if you need the 30A vs. 45A. There are also limitations to start/stop cycles per hour, so if more than 4 than may need to look at VFD's or a soft starter that supports that.

Soft Starter, Compact, 3 Phase, 10hp, 30 Amps, 208

Soft Starter, Compact, 3 Phase, 10hp, 30 Amps, 208-480V, Variable Torque, Built In Bypass, Please Note The Suffix Update From EPZ to TPZ Was Only Due to A New Manual Included

www.wolfautomation.com

Soft Starter, Compact, 3 Phase, 15-30hp, 45 Amps,

Soft Starter, Compact, 3 Phase, 15-30hp, 45 Amps, 208-480V, Variable Torque, Built In Bypass, Please Note The Suffix Update From EPZ to TPZ Was Only Due to A New Manual Included

www.wolfautomation.com

Soft Starter, 34 Max Amps, Chassis w/ Built-InBypa

Soft Starter, 34 Max Amps, Chassis w/ Built-InBypass, Simple Start Control w/ Motor Protection

www.wolfautomation.com

 

[deakin]

Cost of a VFD will be more than a soft start, if you do not need any of the other VFD features. There is some derating of VFD's when run off of RPC's, typically I just add a DC choke which decreases THD/current peaks. I would look at a soft staarter run off the RPC to the motor. WEG makes some reasonable cost ones would need to see if you need the 30A vs. 45A. There are also limitations to start/stop cycles per hour, so if more than 4 than may need to look at VFD's or a soft starter that supports that.

Soft Starter, Compact, 3 Phase, 10hp, 30 Amps, 208

Soft Starter, Compact, 3 Phase, 10hp, 30 Amps, 208-480V, Variable Torque, Built In Bypass, Please Note The Suffix Update From EPZ to TPZ Was Only Due to A New Manual Included

www.wolfautomation.com

Soft Starter, Compact, 3 Phase, 15-30hp, 45 Amps,

Soft Starter, Compact, 3 Phase, 15-30hp, 45 Amps, 208-480V, Variable Torque, Built In Bypass, Please Note The Suffix Update From EPZ to TPZ Was Only Due to A New Manual Included

www.wolfautomation.com

Soft Starter, 34 Max Amps, Chassis w/ Built-InBypa

Soft Starter, 34 Max Amps, Chassis w/ Built-InBypass, Simple Start Control w/ Motor Protection

www.wolfautomation.com

that was also a thought - should i get a larger than 10hp ss or vfd.

 

[mksj]

You have not defined what machine it is, how often it needs to start, and the running load/draw/voltage. With a VFD, there are two options, one run off of the RPC vs. one run from single phase. Recently went through a similar discussion of sizing a VFD for a 15Hp compressor running off of single phase. I am not sure a straight 10 Hp VFD would run off an RPC to drive a 10 Hp motor, really depends on the model, the output under heavy load and the overload % rating. I probably would go with a 15 Hp to give you some head room. The price of the Fuji's compact series is hard to beat.
Fuji 10 HP LSLV0075C100-2 is HD rated for 10 Hp, so should work with a DC choke and runs $405. https://www.wolfautomation.com/vfd-hd-10hp-32a-200-240-vac-3-ph-ip20/
The Fuji 15 Hp which could also be run off of the RPC runs around $570 https://www.wolfautomation.com/ac-drive-15hp-230v-3-phase-33386/
If running single phase input (no RPC) then a Fuji 20 Hp FRN0060C2S-2U will run $650 https://www.wolfautomation.com/ac-drive-20hp-230v-3-phase-33387/

If running a soft start, then would need to address frequency of starts and any derating or configuration for running off of a RPC. The AuCom is not limited with regard to soft starts, the WEG is. Cost wise it is a close call, but a VFD would take up more space and be a bit more complex to install in the end. The soft starters like the AuCom soft starter would be their 10 Hp model would probably be the easiest to install and also has overload protection for both start and run, but still needs to run off a breaker or fusing. Probably worth discussing with Wolf technical to find what the best fit is for your application, and get a warranty. It looks like the Fuji LSLV0075C100-2 running off your RPC might be your least expensive option, otherwise you might consider 20 HP VFD with single phase input. Another factor may be availability/stock, many distributors are out of VFD's.