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- Oct 14, 2014
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25hp 3phase converter with load center
*Reposted from another forum - summer 2014 project*
My son is building a new shop. He's one hell of a machinist and CNC programmer, but challenged with electricity. So, I'm building a deluxe converter setup he won't outgrow.
For an overview, this will be a two motor system with a 5hp used to start a 20 hp phase converter motor. The 20 could easily be larger if more power is ever needed. The system will feed a 3 phase load center panel so all he has to do is add a breaker and wiring any time another machine is added.
Couple design details, the system uses no start capacitors, only run caps. Turns out the amount of capacitance needed to start a 5hp. is almost exactly what is needed to balance voltages on a 25 hp running unit. He's also adding voltmeters to monitor voltages and plenty of spare/extra caps to quickly change things if one leg runs too high/low on voltage.
The deal we struck - he does all the heavy duty power wiring. I'll come in and do the control wiring and system tuning.
I gave him this long message for working notes:
Wiring cookbook. Print this out and check off everything twice.
A: MAIN TO 3 PHASE
Two 100 amp wires from 100 amp fuse in main panel to top of 3 phase load center
Suggest red tape on L1 leg and blue on L3
Neutral from Main to 3phase neutral lugs
B: 3 PHASE TO CONVERTER PANEL
Find correct breaker size for a 25 motor. (probably 40) Run three correct size wire to top of 25 contactor.
(I always do Red tape on L1, on Yellow L2 “wild”, blue on L3. Note: many installs put the wild on L3, Decide now which way to go forever. Do this on every wire both ends ALLWAYS on all your 3 phase power wiring) Bad things will happen if you ever cross these legs
Also do same for 5 hp. contactor. Pretty sure you want 20 amp and #12 wire here. if you want voltmeters, go from top of 5 hp contactor to the meters. Detail, wires going to a door should all go to same location beside the hinge, the run parallel to the hinge for several inches and then on to the door.
Neutral from 3 phase lugs to a small terminal strip in converter panel. Use white #12 wire.
You’ll also run a power wire from a small 1 phase breaker. See logic wiring.
C: PANEL TO MOTORS
Wires from bottom of contactors to each motor. Check you have the right size contactor heaters (overloads). Also look at attached for motor lead wiring. ID your legs with tape.
D: CAPACITORS
Two #12 wires from L1 5hp motor contact to left side of top and bottom caps in column one. Jumper wires between each cap in use. lets start with 400 MFD
Two #12 wires from L2 wild 5 hp motor contact to right side of top and bottom caps in column two. Jumper wires between. same 400 MFD.
Two #12 wires from L3 25hp motor contact to left side of top and bottom caps in column two. Jumper wires between each cap in use. lets start with 400 MFD
Two #12 wires from L2 wild 25 hp motor contact to right side of top and bottom caps in column two. Jumper wires between. same 400 MFD.
Note: then we can just add or remove jumper wires to change amount of caps
E: LOGIC WIRING
Self latching Master Control Relay (MCR)
wire connection 1 connection 2 purpose
1 common^ pin 2 common
2 110 breaker green PB NO start switch
3 green PB NO pin 7 close relay
4 110 breaker * red PB NC stop switch
5 red PB NC pin 6 relay latch
6 pin 8 pin 7 relay latch
motor 1 contactor
11 common^ contactor coil common
12 110 breaker * pin 1 MCR start power
13 pin 3 MCR contactor coil close contactor
motor 2 contactor
21 common^ pin 2 timer relay common
22 common^ contactor 2 coil common
23 pin 3 MCR pin 7 timer relay start timer
24 pin 7 timer relay pin 8 timer relay contactor 2
25 pin 6 timer relay contactor 2 coil start motor 2
* can also put at green PB wire 2 node
^Use white wire for common
*Reposted from another forum - summer 2014 project*
My son is building a new shop. He's one hell of a machinist and CNC programmer, but challenged with electricity. So, I'm building a deluxe converter setup he won't outgrow.
For an overview, this will be a two motor system with a 5hp used to start a 20 hp phase converter motor. The 20 could easily be larger if more power is ever needed. The system will feed a 3 phase load center panel so all he has to do is add a breaker and wiring any time another machine is added.
Couple design details, the system uses no start capacitors, only run caps. Turns out the amount of capacitance needed to start a 5hp. is almost exactly what is needed to balance voltages on a 25 hp running unit. He's also adding voltmeters to monitor voltages and plenty of spare/extra caps to quickly change things if one leg runs too high/low on voltage.
The deal we struck - he does all the heavy duty power wiring. I'll come in and do the control wiring and system tuning.
I gave him this long message for working notes:
Wiring cookbook. Print this out and check off everything twice.
A: MAIN TO 3 PHASE
Two 100 amp wires from 100 amp fuse in main panel to top of 3 phase load center
Suggest red tape on L1 leg and blue on L3
Neutral from Main to 3phase neutral lugs
B: 3 PHASE TO CONVERTER PANEL
Find correct breaker size for a 25 motor. (probably 40) Run three correct size wire to top of 25 contactor.
(I always do Red tape on L1, on Yellow L2 “wild”, blue on L3. Note: many installs put the wild on L3, Decide now which way to go forever. Do this on every wire both ends ALLWAYS on all your 3 phase power wiring) Bad things will happen if you ever cross these legs
Also do same for 5 hp. contactor. Pretty sure you want 20 amp and #12 wire here. if you want voltmeters, go from top of 5 hp contactor to the meters. Detail, wires going to a door should all go to same location beside the hinge, the run parallel to the hinge for several inches and then on to the door.
Neutral from 3 phase lugs to a small terminal strip in converter panel. Use white #12 wire.
You’ll also run a power wire from a small 1 phase breaker. See logic wiring.
C: PANEL TO MOTORS
Wires from bottom of contactors to each motor. Check you have the right size contactor heaters (overloads). Also look at attached for motor lead wiring. ID your legs with tape.
D: CAPACITORS
Two #12 wires from L1 5hp motor contact to left side of top and bottom caps in column one. Jumper wires between each cap in use. lets start with 400 MFD
Two #12 wires from L2 wild 5 hp motor contact to right side of top and bottom caps in column two. Jumper wires between. same 400 MFD.
Two #12 wires from L3 25hp motor contact to left side of top and bottom caps in column two. Jumper wires between each cap in use. lets start with 400 MFD
Two #12 wires from L2 wild 25 hp motor contact to right side of top and bottom caps in column two. Jumper wires between. same 400 MFD.
Note: then we can just add or remove jumper wires to change amount of caps
E: LOGIC WIRING
Self latching Master Control Relay (MCR)
wire connection 1 connection 2 purpose
1 common^ pin 2 common
2 110 breaker green PB NO start switch
3 green PB NO pin 7 close relay
4 110 breaker * red PB NC stop switch
5 red PB NC pin 6 relay latch
6 pin 8 pin 7 relay latch
motor 1 contactor
11 common^ contactor coil common
12 110 breaker * pin 1 MCR start power
13 pin 3 MCR contactor coil close contactor
motor 2 contactor
21 common^ pin 2 timer relay common
22 common^ contactor 2 coil common
23 pin 3 MCR pin 7 timer relay start timer
24 pin 7 timer relay pin 8 timer relay contactor 2
25 pin 6 timer relay contactor 2 coil start motor 2
* can also put at green PB wire 2 node
^Use white wire for common
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