PTO generator

[tommu56]

This digital monitor comes with 4 wrap around clamps 2 large and 2 small. I clamped one around each of the incoming load legs from the meter. The probes then plug into the back of a small transmitter that will send the signal a couple of hundred feet to the receiver. It gives a read out in real time and stores a 2 year log I believe. The whole shebang is battery powered.

View attachment 287963

PineRige
do you have a link this meter sounds interesting

tom

 

[PineRidge]

PineRige
do you have a link this meter sounds interesting

tom

Here you go Tom energy monitor

 

[fred239]

All motors draw locked rotor current at startup because the rotor is stationary at that time. This is a very short term event that you will need a peak holding meter or an oscilloscope setup to capture because the current drops quickly as the motor starts to turn and continues to drop until it reaches speed.larry

Just an update on surge amps; we tested the instantaneous surge and it came upto 270amps for just a fraction of a second, while running amps was only 39-40amps at each of three legs. the motor was rated at 63.5 amps/208volt/3phase, and the 270amp starting surge has never tripped the 100amp main breaker. so I am totally confused and back to the beginning. 39x208x1.73=14,000watts. at 3X overhead would I need a 42kW generator to start this elevator? My average running load is only 8kW with a 5 minute peak of 17.5kw- so this sounds like a very inefficient setup, as the specs show fuel consumption per kWhour to be 50% less efficient at half load. Worse yet, 8kW/42kW is closer to 19% of full load. Any thoughts?

 

[DarkBlack]

Fred, 270 amps won't trip most 100 amp breakers, unless it was for a longer time period( over 1 second ). I've skipped most of this thread, but I will offer that you probably used a meter that doesn't show real power( if you didn't have 4 clamp-ons and 4 voltage probes, then you didn't ). In this case your amp based power calculations will come out too high.

One trick used to bring up high inerta, high currnet draw 3ph motors is to connect them for Y-start, delta run. In your case you would probably need to spend a few buck on some realys to make it happen, otherwise you can put in a cheap VFD. In either case the mods woud be cheaper than a larger generator needed without them.

 

[yelbike]

Just an update on surge amps; we tested the instantaneous surge and it came upto 270amps for just a fraction of a second, while running amps was only 39-40amps at each of three legs. the motor was rated at 63.5 amps/208volt/3phase, and the 270amp starting surge has never tripped the 100amp main breaker. so I am totally confused and back to the beginning. 39x208x1.73=14,000watts. at 3X overhead would I need a 42kW generator to start this elevator? My average running load is only 8kW with a 5 minute peak of 17.5kw- so this sounds like a very inefficient setup, as the specs show fuel consumption per kWhour to be 50% less efficient at half load. Worse yet, 8kW/42kW is closer to 19% of full load. Any thoughts?

That's why systems are sized according to code table and not assumptions. Breakers are size according to their respective rating( whether they are %100 rated (rare) or 80%(most common type). Their are so many tripping charactistics that even the code requirement have built buffers. Typically breakers are rated at 125-150% for rated FLA current and td fuses are at 250%. Don't try to hard too understand as I still refer to charts, I'm a construction and power electrician with a back ground in marine systems with 16 years experience.

 

[fred239]

... I will offer that you probably used a meter that doesn't show real power( if you didn't have 4 clamp-ons and 4 voltage probes, then you didn't ). In this case your amp based power calculations will come out too high.

Thanks, you are correct. We used a digital ammeter and I've been told by the electrician that an instantaneous digital reading could be twice as high as an analogue reading. I will try to learn more about "Y-start, delta run", and a "VFD". wikipedia has been very helpful. thanks again.

 

[PineRidge]

Variable Frequency Drive

 

[SPYDERLK]

Just an update on surge amps; we tested the instantaneous surge and it came upto 270amps for just a fraction of a second, while running amps was only 39-40amps at each of three legs. the motor was rated at 63.5 amps/208volt/3phase, and the 270amp starting surge has never tripped the 100amp main breaker. so I am totally confused and back to the beginning. 39x208x1.73=14,000watts. at 3X overhead would I need a 42kW generator to start this elevator? My average running load is only 8kW with a 5 minute peak of 17.5kw- so this sounds like a very inefficient setup, as the specs show fuel consumption per kWhour to be 50% less efficient at half load. Worse yet, 8kW/42kW is closer to 19% of full load. Any thoughts?

You have a momentary 100KW load when that motor starts to start. DarkBlacks point of no V measurement is true, but not material here because the motor wants those AMPS and when youre on mains you have a hard voltage source providing ample "pressure" to push those amps. The same would be true if your mains connection were replaced by a ~90 or 100KW gen. The question for choosing a gen as low as 40KW or lower is how sensitive is the rest of your system to a relatively long and deep brown out. That brings the question of whether there are significant compressors running when starting the elevator motor. They could stall and cause system current demand to avalance upward. Next is what kind of load is that elevator motor starting under. Im guessing that it is a load that presents only inertial load at 1st movement, but that a real pumping load develops as rpm increases. What bothers me is the high apparent load you figure indicates on the running motor. Is the elevator rising during that measurement. If it is not I would expect to see a significantly lower "idle" current ... perhaps 10A.

It is premature at this point but I anticipate the need for a 40KW gen driven in an underpowered mode by an engine in the neighborhod of 30+ HP [capable of supporting your sustained 17KW max loading]. Depending on the nature of your composite load, this value gen should not show debilitating voltage buckling under your peak load and "flywheel" inertia will ride thru the brief momentary overload to the engine.
larry.

 

[fred239]

You have a momentary 100KW load when that motor starts to start... What bothers me is the high apparent load you figure indicates on the running motor. Is the elevator rising during that measurement. If it is not I would expect to see a significantly lower "idle" current ... perhaps 10A.larry.

It's a hydraulic elevator, 39amp(x1.73 for three phase) max load only rising upward, downward is mostly a release of pressure, but we will remeasure and check the current in the down mode as well. I will also inquire about the costs of installing a VFD. Otherwise, there are no compressors running, just the hot water circulating pump which stays constant on for about seven months, and then the boiler burner fan, which does cycle, but it is a small 5amp 208v motor. Flourescent lighting ballasts are constant on, the only other starting loads would be an occaisional washing machine @ 120v. Power company has confirmed that 17.6kW "actual" as opposed to billed demand, has been the maximum in the past five years.

 

[fred239]

... I anticipate the need for a 40KW gen driven in an underpowered mode by an engine in the neighborhod of 30+ HP [capable of supporting your sustained 17KW max loading]. Depending on the nature of your composite load, this value gen should not show debilitating voltage buckling under your peak load and "flywheel" inertia will ride thru the brief momentary overload to the engine.larry.

Thank you larry, that is a great idea. I hadn't considered a custom pairing, but it will be unlikely that I will find a pre-owned system like that. Do you have any advice regarding the VFD?

 

[aczlan]

If you are looking for something diesel, look at a MEP-004(15KW) or MEP-005(30KW) Military Surplus generator.
Both ratings are "Prime" (ie: what it can put out 24x7) at 5000' of elevation and 120F ambient temperature. Both models are also 3 phase and soildly built.
Sewerzuk on here has quite a bit of experience with them.

Aaron Z

 

[jmcmurray]

The province did a study of the quality of power (and many other factors) when using PTO driven generators.Tractor-Driven Generators: Producing Quality Power

Somewhere in there they even try the 1000 PTO run at half throttle idea.

 

[SPYDERLK]

The province did a study of the quality of power (and many other factors) when using PTO driven generators.Tractor-Driven Generators: Producing Quality Power

Somewhere in there they even try the 1000 PTO run at half throttle idea .

Very unstable to load changes.

 

[SPYDERLK]

Thank you larry, that is a great idea. I hadn't considered a custom pairing, but it will be unlikely that I will find a pre-owned system like that. Do you have any advice regarding the VFD?

Variable frequency drive? ... Soft start technology? I think this can definitely limit the hi inrush. It is very applicable on fans and anything that starts similarly under "no load" conditions. Many pumpers of liquid can qualify as starting under semi load -- a harder start scenario not necessarily applicable to the SST ... but maybe. Study up and youll easily know more than I.
... I still cant get a grasp on your elevator motor start and I think the load mode it starts under will be very important. Does the motor only run when the elevator is moving? - or start 1st and then you select up/down.
larry

 

[RickB]

Very unstable to load changes.

Not much different from any other engine driven genset. The closer one gets to using all the available engine power, the more variable the product is. I monitor voltage and frequency with an inexpensive Kill-A-Watt unit plugged in a kitchen outlet.
I get along fine with my 885 Case running my alternator at 1100 ERPM so long as I don't run my central A/C unit.

 

[fred239]

... I still cant get a grasp on your elevator motor start and I think the load mode it starts under will be very important. Does the motor only run when the elevator is moving? - or start 1st and then you select up/down. larry

The motor only runs when the elevator is moving up or down, it runs a hydraulic pump. It's only a three storey elevator, like a big hydraulic jack.

 

[SPYDERLK]

Not much different from any other engine driven genset. The closer one gets to using all the available engine power, the more variable the product is. I monitor voltage and frequency with an inexpensive Kill-A-Watt unit plugged in a kitchen outlet.
I get along fine with my 885 Case running my alternator at 1100 ERPM so long as I don't run my central A/C unit.

Theres a combination of factors that make it less stable; 1] As you say, you are using a higher proportion of the power available as a result of almost twice the engine torque required at its lower rpm, 2] due to the higher pto gearing the gen rpm changes almost twice as much with a given change in engine rpm. ... Even if the engine has the power to support the full load range youre asking twice the exactness from the governor.
larry

 

[RickB]

Theres a combination of factors that make it less stable; 2] due to the higher pto gearing the gen rpm changes almost twice as much with a given change in engine rpm. ... Even if the engine has the power to support the full load range youre asking twice the exactness from the governor.
larry

That is a variable I hadn't considered.
In my particular circumstances, I don't forsee any changes. The power quality is sufficient, the tractor maintains a decent engine temperature, and there is no slobbering or wet stacking. And it ran on about 2 quarts per hour of Diesel fuel over 18 or so hours of run time during and after Sandy. In fact I just changed the fan belt on it today as an act of preventative maintenence. Certainly don't want it to toss a belt while I am inside nice & comfy watching TV.

 

[SPYDERLK]

The motor only runs when the elevator is moving up or down, it runs a hydraulic pump. It's only a three storey elevator, like a big hydraulic jack.

... Does the motor reverse direction or is elevator direction controled automatically by valving according to which button u push. If you push down on the lowest floor does the motor start? Sofar its sounding like a full load start anytime youre going UP. What happens when the elevator is heavily loaded?
larry

 

[fred239]

... Does the motor reverse direction or is elevator direction controled automatically by valving according to which button u push. If you push down on the lowest floor does the motor start? Sofar its sounding like a full load start anytime youre going UP. What happens when the elevator is heavily loaded?
larry

Motor does not reverse, does not start on down on lowest floor. Maybe a full load start, will check about an unloader start valve. My guess is that heavy loads will use only slightly more current as the car and jack shaft are pretty heavy already. Thanks for your advice, and Happy Thanksgiving.