converting dc motor load to ac

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aaron peker

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lakewood
I have 4 elevators identical with the following info. I'm looking to size a AC ups backup for these elevators
the name plate on the motors is :
amps 155
DC 240v
hp 41
RPM 74.5
Size 74

Since the motors are DC I guess the elevator controller converts to building 208V AC to DC - does the load change in the conversion process and what other info do I need to know to size the UPS
Please advise
ty
 
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GoldDigger

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Continued.

Continued.

Bring in an elevator expert, please.....

DC motors are often used for winding drum type elevators (modern elevators are traction type, with the cable looping around the drum). Winding drum type elevators are very much dependent on proper operation of the motor(s) at all times, so I would not trust to internet device for the specs of a UPS.
 
Tony S

Tony S

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Location
Resting under the Major Oak UK
You are entering a minefield blindfold.

The motor plate my say 240V, have you given any consideration to the speed/direction/braking systems? You become responsible for a huge can of worms in the event of damage, malfunction or god forbid injury/death.
 
I

Ingenieur

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Earth
DC is used for traction machines
quite common
a SS DC controller is used, the armature current/voltage is modulated to contol torque anf the field for speed
ABB is a common mfg http://new.abb.com/drives/dc/dcs800-s
it will have outputs for the armature and field

calculate the dc power required
basically rated arm i x v plus field i x v for each unit
the machine brake is dc also
and you'll need some va for the controls, a few kva should do it
add 30% for losses, pf, eff

this will be a huge ups and not sure A17.1 allows it
it is usually a dedicated generator
 
I

Ingenieur

Senior Member
Location
Earth
GoldDigger said:
Bring in an elevator expert, please.....

DC motors are often used for winding drum type elevators (modern elevators are traction type, with the cable looping around the drum). Winding drum type elevators are very much dependent on proper operation of the motor(s) at all times, so I would not trust to internet device for the specs of a UPS.
Click to expand...

winding drum machines are very seldom used due to code
limited travel 40' iirc
speed 200 fpm
single rope

traction is most common
with hydraulic for low travel
and rack & pinion for special applications

the last 1/2 dozen or so machines I commissioned 5 were dc traction
1 was a geared ac
 
Jraef

Jraef

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Electrical Engineer
If this is a passenger elevator, anything used in it involves life/safety and must be listed/certified for elevator use. As mentioned, you are entering a minefield blindfolded. Your risk exposure is not just financial, it may be bordering on criminal if anything happens. Leave this to certified elevator mechanics.
 
I

Ingenieur

Senior Member
Location
Earth
Jraef said:
If this is a passenger elevator, anything used in it involves life/safety and must be listed/certified for elevator use. As mentioned, you are entering a minefield blindfolded. Your risk exposure is not just financial, it may be bordering on criminal if anything happens. Leave this to certified elevator mechanics.
Click to expand...

you'd be surprised how few system components are actually required to be certified
they are listed in A17.1 Part 8
stuff like door switches, buffers, etc

very little electrical power equipment
the NEC is referenced for those standards
the requirements for emergency or stand-by power are defined in A17.1 section 2.27.2
key points
operate at least 1 elevator at rated load
automatic transfer
indication when not on normal power

it does not preclude use of a UPS
in fact does not spec a method
the code is not prescriptive but performance based (as related to this work)

for liability purposes (and most likely required by law) this work should be done by a licensed professional
not a mechanic but a PE with experience in this type of work
 
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Besoeker

Besoeker

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UK
Jraef said:
If this is a passenger elevator, anything used in it involves life/safety and must be listed/certified for elevator use. As mentioned, you are entering a minefield blindfolded. Your risk exposure is not just financial, it may be bordering on criminal if anything happens. Leave this to certified elevator mechanics.
Click to expand...
Well said.
 
I

Ingenieur

Senior Member
Location
Earth
I've worked with this company recently, motion control
they make a ups package to do this

if the car + load > counter weight (car tends to fall) lower car to next landing
if the car + load < counter weight (car tends to rise) raise to next landing

in essence, no motive power, only motor braking for a very short duration
interesting
 
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Jraef

Jraef

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San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
I too have done a lot of work with Motion Control Engineering for their retrofit elevator controls. That's where I learned just how tough it is to get the proper certification on components used in the power circuit. We did contractors and soft starters for them, the UL standards were easy, but their industry demanded that they get CSA listing for passenger elevators because their test standards were a LOT more stringent in terms of duty cycles, failure modes etc. Of all soft starters they vetted, only two passed the CSA testing (within the price range they demanded). The same was true just for contactors, although more suppliers qualified those. The testing however was very expensive so some suppliers don't even bother. So test, they sell a UPS product for elevators, but it has Ben tested and certified for the use, and they only sell it to elevator service companies.
 
junkhound

junkhound

Senior Member
Location
Renton, WA
Occupation
EE, power electronics specialty
NYC?

NYC?

OP location simply says 'lakewood' - as in Lakewood NJ and he is doing work in NYC ?

Just curious, have not seem much in trade discussions for a few years on how the old building elevators in NYC are being maintained. Maybe OP is working compliance with some new requirement for NYC elevators promulgated by buddy BilldB ?

Lots of really old stuff on some NYC elevators, very specialized antiques.
http://www.coned.com/newsroom/news/pr20071115.asp
 
I

Ingenieur

Senior Member
Location
Earth
Besoeker said:
They have those in the pink trade in the far east.

Much more seriously, when it comes to the transport of people it's a different ball game. No pun intended.
Lives are at risk if you get it wrong.

http://www.cruiselawnews.com/2015/1...-shows-aftermath-of-deadly-elevator-accident/
Click to expand...

don't know what the 'pink trade' is?

I work with elevators that lower miners >1000 ft into the earth so the consequence of failure are not unknown
I am on the national A17 ASME standards committee so we look for failure modes
modern elevators are extremely safe machines
NYC has like 60000 of them yet fatalities are rare, much lower per capita/unit distance than cars

we had a failure that led to a new requirement: ascending overspeed protection
lightly loaded car, cwt pulls car up, hit head frame, slammed occupants off the car ceiling, you could see the body imprint left by the rock dust on their coveralls
now rope grippers or bode brakes with associated controls are required to prevent this
 
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