I'm interested in how much the temperature of a thin oil film will rise over a short period of time after it applied to a warmer metal surface, such as splash-lubricated cylinder wall in an engine.
I'm okay with assuming that the metal surface stays at a constant temperature, if that makes the...
I've been thinking of using a buck boost transformer to boost from 208V to 236V single phase for a 230V stove that requires a 120/240V 50A receptacle. GE recommends using these transformers for some of their appliances.
The obvious concern is that the appliance requires 120V for lighting and...
I'm considering installing arc flash detection equipment to trip upstream breakers instantaneously in the case of an arc flash event. My question is whether this equipment can be of any use in instances where the arcing fault current is already expected to be high enough to trip the breaker on...
I'm planning on using a digital metering system (Allen Bradley PowerMonitor 1000), and I require fairly accurate readings below 5% of the CT rating. IEEE C57.13 defines CT accuracy from 5% to 100% of the CT rating, but not below 5%.
What kind of accuracy can I expect in the 1% to 5% current...
We upgraded a water pump to 50hp and added a solid state soft starter. We have an existing 60kW Cummins gas genset that will start up the pump most of the time, but often surges once the pump is almost up to speed, struggling to keep a constant speed. Sometimes the generator trips on overspeed...
I have a 600V 250hp drive that sometimes trips on "Overbraking", when requested to run. This fault occurs when the DC bus voltage reaches 1174V. The same motor has caused this fault when connected to three different drives. Our other 250hp motor does not cause its drive to trip.
The drives...
I've hired a company to perform a coordination study for a facility and I'm reviewing their recommendations. The system is 600V, with an 800A main breaker with LSI trips and adjustability. The largest downstream overcurrent devices are 400A drive fuses.
The study recommends that the main...
I'm designing a system with a standby generator (~150kW), where most of the load will be 6 pulse VFD's. The generator will be sized to account for the additional heating in the alternator due to the harmonic currents.
My question is, what is an acceptable limit for harmonic voltage...
I'm in the process of designing a system where there will be several 75kVA 600V-120/208V three phase transformers. I wish to switch the primary of each transformer with a contactor. The load on the secondary of the transformer will be almost entirely resistive. I'd like the contactor to be...
I have been asked to evaluate the possibility of using high resistance grounding (HRG) for a new facility. The primary reason is to reduce the possibilities of downtime and equipment damage.
The electrical service is 600V, 800A, supplied by a 500-750kVA utility transformer. The main loads are...
We have some remote instruments that are fairly critical to our process and it has been suggested that a CDMA cellular modem be used to send the signals to the plant PLC.
Can anybody comment on the reliability of cellular modem service versus conventional modems with a leased line or dialup...
I'm at the conceptual stage of a facility design where we plan on using two 700-800hp pumps on VFD's. They may run simultaneously and we will have a standby genset. Cable lengths are relatively short. Building loads will be 50-75kVA. A 600V service would be in the 1600-2000A range (provided...
I would like to know the extent to which different factors affect oil temperature for a typical gasoline engine, including ambient temperature, RPM, and engine load.
Does anybody know of papers or studies that quantify this?
I am planning on running two sets of four single core #4/0 conductors in parallel PVC conduits. The raceways and conductors will be identical in size and length. Since the individual conductors will be pulled through each raceway, the conductor orientation and hence reactance may be slightly...
I'm designing a facility that has several 150-250hp pump motors on VFD's. The distance from the VFD's to the motors is less than 50ft. The motors will be inverter duty rated. The cables can either be armored cable with 1000V insulation, VFD cable, or individual wires with 1000V insulation...
I am sizing a gas genset to start a 600V 45kW motor driving a centrifugal pump. Motor characteristics are as follows:
Starting Current: 405A
Rated Current: 54A
Total Moment of Inertia: 0.42 kgm2
Speed: 1775rpm
Load at pump operating point: 32kW
Motor starting power is the limiting factor for...
I am adding a 30hp, 240V centrifugal pump load to a 150kW gas genset. The pumphouse will be at the end of a 1000ft 480V feeder, and also has some small lighting and heating loads. A 75kVA transformer will step the voltage down from 480V to 240V (3 phase).
I'm concerned that the voltage dip...
I have two 600V cables in a facility that are the same size and length. They were hipot tested at 2150V and the results are as follows:
Cable 1: 5000 Megohm, 0.452uA
Cable 2: 100 Megohm, 21.5uA
Are there any rules of thumb for pass/fail? I've read that on Megger tests, the low limit is...
Does anybody have experience with these gas gensets in the 50-250kW range? As a consulting engineer, I normally specify Cummins gensets for my clients, and have accepted Kohler and Caterpillar gensets as equal products, but I am not confident in the Generac gensets.
Their 70kW set has a 6.8L...
We have a couple of 600V cables in our facility that have been somewhat damaged. The outer jackets of these cables have be compressed (squished) somewhat in one spot. They are #6 AWG SOW cables (non-armored equipment cable) used to supply 600V motors.
We may replace them just to be sure, but...
