We develop various test systems based on VFD driven dynamometer motors (both induction and PM, range 200-3000 kW). In most cases, the motor cable selection is very critical due to required flexibility. We use NEC Art.430.6(C). Its scope perfectly fits a definition of Adjustable Speed Drive...
Dear colleagues, please advise on the following: typical VFD cable has three symmetrical ground conductors. Can I combine these three ground conductors together and crimp all of them in a single larger compression lug? The site location is in the USA. Will this arrangement be acceptable. or this...
We order from Europe electrical equipment that complies with the following EU standards:
EMC Directive EN61326-1:2013
Low Voltage Directive EN61010-1:2010
Machinery Directive EN ISO 12100:2010
RoHS Directive EN50581:2012
CE Marking
The end user in USA specifically requires that the equipment...
Thank you, CSWILSON. You made a good point. This specific motor has values of Ld/Lq around 30 microhenry (and not milliHenry's range). Probably, they require another 20 microHenry to minimize thermal effect of current ripples. We just never saw before such justification of additional inductance.
We have a specification of PM synchronous motor driven by VFD. The motor spec requires external inductance about 20 microHenry. Our understanding was that this inductance is required to reduce dv/dt of PWM voltage pulses, thus reducing a stress applied to motor insulation, reducing accelerated...
We used to refer for inverter duty motor specifications to the standard NEMA MG1, part 31 (for US built motors) and IEC 60034-17 (for EU motors). The NEMA MG1 Part 31 applies only to squirrel cage induction motors. What document/standard (if any) would apply to inverter fed synchronous PM motors ?
Wea are a big international company, currently bidding for a project in California. The VFD based test systems are standard products for our EU arm. Their (local) VDF supplier has declined seismic compliance requirements. We try to help them to find a suitable replacement for standard VFD. I...
Dear colleagues,
We consider application of VFD systems [range (300-700)HP] in the area El Monte, California.
Can anybody refer to EU VFD supplier that would provide seismic rated VFD cabinets?
Our equipment has to have UL listed/recognized components. Some of currently used components have been built to MIL standards. Do we still need to replace them with UL compliant parts, or MIL compliant parts could be acceptable? Is there any general consensus about that?
The VFD operates at 575V, fed by step-up drive isolation transformer 480/575V. Inside that VFD, there is a switching DC power supply (input power three phase, 400V) fed from a dedicated 400VA control transformer 575/400V. This power supply has failed (as we assume, the failure could be...
Generally speaking, most VFD suppliers are reluctant to idea of separation the inverter(s) from the front end converter. We had a 3 MW VFD systems with 4 inverters, and decision to separate inverter sections has been made only after modeling of overall DC bus extension system. The critical...
Thanks for your responses, gentlemen. We found out the source of our confusion - the fact that above the base speed VFD supplies to the motor additional reactive current component to reduce the flux (field weakening simulation) in order to limit raise of the motor generated back EMF at higher...
Thanks for response, Keith. A bit more details. This is a test stand for 4WD vehicle transmission testing, with 4 PMSM wheel dynamometers(absorbers) and a common DC bus VFD system. We selected input drive transformer kVA rating (reduced comparing with rated for full scale system size)based on...
Please advise: for VFD system (unity PF at AFE) with PM synchronous motor - how to estimate total power/current consumed from the grid when the motor is spinning up to max speed with no shaft load.
Yes, I understand that. The insulating coating is fractured in several spots and have missing pieces exposing bare metal. As we read in published white papers, the outer ring coating is not the best method of insulation (could be the cheapest). We will suggest the motor MFG to use ceramic ball...
We are analyzing a bearing failure on VFD driven PM motor. Motor MFG uses DE and NDE insulated bearings (brand AKN, Germany) and DE ground brush. These bearings have the outer ring surface coating (medium grey color). This seems to be either ceramic or aluminum oxide insulating provision...
This could be a very simple question, but after many years in electrical engineering I suddenly realized that can not determine voltage classification of the VFD system (enclosure) that has input voltage 575V AC and DC bus voltage 850 V DC. Is such equipment classification considered to be below...
Gentlemen, thanks for your inputs, very informative and useful. The very last sentence in Bill's posting actually repeats my OP. Yes, we will try to keep the whole 3 MW regen system intact, and add to it a large energy sink. We thought, the best way would be to add DC resistive load bank...
