Starter for 50 hp Delta, 9 lead motor.

[Ken73]

I am trying to come up with a way to hook-up a 50 Hp, 3PHZ, 9 lead Delta motor that runs a VERY large plainer. Was told that it needed a "soft Start" to use the equipment, this probably due to the direct drive to the plainer that uses 6" wide flat belts to turn the componants on the plainer. The kicker is that I am trying to use what I have. That is a set of interconnected Culter Hammer starter contanctors (rated for 50 hp) 3 Heater resistors, Numerious 40amp contacter relays, and 2 push button stations. The motor is an inductive type, with a 1.5 PF, 220/440 volt, I think the motor type was a "K". Rated run amperage was 119 @ 220 / 59.9 @ 440. Thanks in advance.

 

[Ken73]

I know that there are other ways of starting this motor, for example a Wye - Delta Start. Thats seems more feesable, but how would you connect it when using a 9 lead motor. I understand the function of a resistive starter, just wanted to know if is a smart way to go with that size motor.

 

[DickDV]

Given the materials you list as being available, I don't see softstarting in the picture.

Across the line starting, yes, but not softstarting. Somebody is going to have to spend some money somewhere to get that.

 

[Ken73]

So using the resistive start is a viable option? If not how, if its possible, can I do a Wye - Delta start configuration on a 9 lead Delta motor? If I'm not mistaken that will start the motor at around 58% of its torque rating. Across the line start is a very dangerous start for this peice of equipment, I need to start this with less torque than what across the line would produce to be safe. Thanks for your reply. Oh, say that "soft start" is the only way to go, how and where would I begine to look to find a unit to handle the demands this motor will have?

 

[DickDV]

I don't believe you can get wye-delta start from a nine lead motor. You would need a 12 lead.

To choose an electronic softstarter, you need line voltage, hp or (better)FLA, desired enclosure as in NEMA1, NEMA 12, etc., decide whether you want a combination starter with input disconnect or fused disconnect or CB, and whether you want reversing. Then go to AB, Sq D, Benshaw, Motortronics, ABB, and others for a quote. Once your softstart is operational, you won't regret having done it.

 

[rbulsara]

agree with DickV's last post..

Ken: If mention where you are located..that helps people recommend proper mfrs..

 

[rbulsara]

see this link..if any help to see how 9 leads are arraged.

http://www.patchn.com/tutr-mot.htm

 

[jraef]

Ken,
With a 9 lead motor, it can theoretically be connected Y or Delta internally, but you dont have enough of the winding "ends" brought out to be able to switch from Y to Delta externally for soft starting. Sorry, but it just doesn't work that way.

You also don't have enough parts in your description to do this. Even if you went out and bought resistors, that is NOT a good solution for a planer. The resistors will glow red hot and are prone to catching stuff like sawdust on fire. You could go with a reactor start or an autotransformer start with a Korndorfer connection, but you would still need to find a properly sized starting reactor or autotransformer and a wiring diagram (that you trust).

Since you must buy something, just buy a solid state soft starter like DickDV said. They are probably cheaper and much easier to hook up, especially if you don't have a lot of experience.

"Venditori de oleum-vipera non vigere excordis populi"

 

[aolalde]

Hello Ken73 (Electrical)

My advice is that 50 HP is a dangerous amount power to guess; if you do not have the knowledge and experience. Hire a qualified firm or technician to design and execute that project.

 

[mc5w]

At that power range you will save a lot of money if the soft start is 480 volts. If your power system is 120Y208 volts or 240 volts 3-wire, a standard single phase transformer is 277 volts primary, 120x120/240 volts secondary. You could use three 25 KVA units to create a small ( 100 amp ) 277Y480 volt electrical system. When you reach a point where you need to install a 277Y480 volt service, you can turn around the transformers and use them to power your 120Y208 volt or 240 volt 3-phase stuff.

You could also just simply have a 277Y480 volt service installed particularly if your existing electrical service is rather old. For how much starting current that a 50 HP motor pulls when starting across the line you could put in a 400 amp service using a class 320 meter socket ( if your utility allows on commercial services ) and use two 200 amp service switches. If your utility requires that you use current transformers at this voltage or amperage an economical way to build a 600 amp or 800 amp service is to use three or four 200 amp service switches with 200 amp time delay class J fuses. You could then use 1 service switch directly as the motor branch circuit device. I do not know how much other power you need. National Electric Code allows you to use 6 service switches for a service and that is the most economical way to build a 1600 amp or smaller service. Every time you double the size of a fusible switch or circuit breaker you more or less triple the price.

Also, when you buy this soft start also buy the auxiliary contact that will tell you when the bypass contactor is closed. Hook up that auxiliary contact to a gree light so that you know when to start using the planer. You do not want to use this planer until the silicon controlled rectifiers have been bypassed by the bypass contactor.

You have some of your nameplate information messed up. The power factor can never exceed 1.0, so you probably have a service factor of 1.15 which is an index of how well it can handle adverse mechanical overload.

Seems that you have a starting code letter K motor which would pull would pull 400 to 449.5 KVA ( 481 to 540 amps at 480 volts ) of starting current when started across the line. A more modern motor would pull about 3/4 of that ( about 300 to 378 amps ) when starting and run more efficiently to boot. That is, for how old this motor is and how much extra starting current it draws, you can get the benefits of a soft start and better efficiency by replacing the motor. Design A and design E motors are bad news from a starting current and inrush current standpoint. The original reason for using separate lighting and 3-phase services was that design A motors could not be on the same transformer as the lighting.

Since this machine is subject to cyclic duty which makes cyclic overloading more or less acceptable, size the wires at 140% of the greater full load current or National Electrical Code table 430.250. See NEC table 430.22(E) for periodic duty for a continuously rated motor. This would amount to a conductor rating of 91 amps read 100 amps. Size the conduit to accept 150 amp wire which will make wire pulling easier. The disconnect switch needs to be able to accomodate 150 amp fuses or you could just simply go with a 150 amp circuit breaker see NEC 430.57. If you think that this motor might be subject to varying duty then 130 amp read 150 amp conductors would be needed.

You will never regret using oversize wire or an oversize conduit. It actually PAYS to use an oversize conduit because wire pulling is easier. More electricity will reach the motor if the wires are larger. Remember, when you heat up wires you are paying for electricity and not getting it.

If you decide to upgrade to a more modern motor instead of a soft start check to be sure that your 50 HP motor starter is also rated to carry at least 91 amps of resistance heaters when used instead to control electric heaters. This way, the deliberate overloads that can occur under production conditions will not slow spot weld the contacts and turn your motor controller into something that isn't.

Contacts that are beefier will also last much longer. When a contactor or relay is loaded at 1/3 of full rating the contact life is about 10 times of full rating. That does not mean that you should use a triple size contactor in all applications but rather that small increase in size can reduce maintenance and other costs.

 

[itsmoked]

Which costs less 240V soft start or a transformer and a 480 soft start?

 

[Ken73]

Thanks everyone for your help with this project. Sorry that some of my info was garbbled, I was trying to go off of memory. Also its been over 8 years since I worked with motor controls, motors. Been busy fixing Navy A/C as avaition electrician and now am trying to get back into things. It does sound like I might be in allittle over my head here so I might refer this to a more knowledgable person to tackle. Besides, from what mc5w was saying the available power just isn't there. There is 3 phase power, but its 240 volt. This may wait till the owner upgrades the available power to his warehouse, I beleive he is gong to 600 amps. Thanks again, I'll keep you posted on the outcome.

 

[mc5w]

The owner of this warehouse might as well make the new service 277Y480 volts. This way, if he needs to beef up the lighting he can run it on 277 volts. Most HID ballasts that were installed over the past 15 years have taps for 120,208,240, and 277 volts. Any ballasts and fixtures that are 20 years old need to be replaced anyways - the ballasts are ready to die and the reflector will be absorbing too much light.

Just remember, that 277 volt light switches that are on different phases need to be in different boxes of have barries between. OK to have 2 switches that are on the same circuit or the same phase in the same box, but I would restrict 2 adjacent switches to the same circuit. If he wants individual switches for each fixture Leviton and some others make a triple switch for this voltage and you can put two in the same 4" by 4" box if they are controlling 400 watt fixtures.

 

[mc5w]

I forgot to mention that NEMA ( American ) style motor controllers have to be derated under these other conditions:

1. The starting code letter of the motor is J or higher - please see National Electrical Code table 430.7(B).

2. Jogging duty which is very frequent starting and stopping.

3. What is known a plugging or slamming which is reversing the phase rotation at full voltage while the motor is running. This draws about 2 times locked rotor current.

 

[mc5w]

Also forgot to mention that IEC ( International ) style motor controllers also need to be derated under that same 3 conditions listed above.

 

[petronila]

Hello Ken,

If the motor is 9 lines-Delta connection I think you only have to spend money, sending the motor to repair shop,they are going to convert the 9 lines in a 12 lines.(They have to open the winding and to take out the other 3 lines: 10-11 & 12), with this work donne now you can perform a Wye-Delta Starting using all you have.

Regards,

PETRONILA

 

[fsmyth]

Sorta related: anyone have any pointers to info on
resistor sizing and effects? (Emphasis on _effects_).
All the vendor sites I have viewed seem to assume
that you already KNOW what size you need.
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