Почему подтверждение отключения трехфазного двигателя должно быть представлено до цены запроса цены
When a 3 phase motor trips during startup, I do not quote from kW alone. I ask the buyer to prove the motor nameplate, site voltage, protection setting, starter or VFD method, load condition, and duty before comparing price, because a cheaper electric motor cannot fix a hidden site or machine problem.[С1][С2][С3]
Startup-trip problems usually arrive as an urgent message: "The motor is new, but the breaker trips." Sometimes the buyer wants a bigger 3 phase motor. Sometimes the installer wants a different starter. Sometimes the distributor wants the supplier to accept warranty before anyone has checked the machine.
From the factory sales side, I slow down here. Reddit discussions show the same practical confusion again and again: a motor trips, someone suspects the motor, another person asks about overload settings, phase voltage, load, starter type, or wiring. I use that only as pain-point evidence. The technical buying decision still needs nameplate data, site evidence, and a written RFQ boundary.[С1][С2][С3]
What Proof Should I Send Before Asking for Price?
What Proof Should I Send Before Asking for Price?
For a tripping 3 phase motor, I first ask for a clear nameplate photo, a photo of the starter or VFD panel, the protection device rating and setting, and a short description of when the trip happens. "Trips immediately" is different from "trips after the machine loads material" or "trips after ten minutes."
The old or installed motor nameplate matters because rated voltage, frequency, current, RPM, duty, insulation class, enclosure, and connection method define the baseline. Motor selection guides treat supply, duty, operating condition, and driven equipment as part of the specification, not optional details after price.[С2][С3]
I also ask for the driven machine. A 3 phase motor on a fan, pump, crusher, grinder, compressor, conveyor, or gearbox does not face the same starting load. If the buyer only sends rated power, the supplier is guessing at the part of the job that usually creates the trip.
✓
A startup-trip RFQ is stronger when it includes nameplate data, trip timing, protection setting, starting method, and driven-load context before price comparison. True
These fields let the supplier separate motor selection from site power, protection, and machine-load assumptions.
×
Rated kW is enough to quote a replacement 3 phase motor for a startup-trip problem. False
Rated power does not prove voltage match, current setting, starting condition, duty, or load torque.
Why Check Site Power and Protection Before Blaming the Motor?
Why Check Site Power and Protection Before Blaming the Motor?
A buyer may call it a motor problem, but the first evidence may point to the site. Low voltage, phase imbalance, loose terminals, undersized cable, wrong breaker curve, overload setting mismatch, or a starter selected without enough margin can all appear to the purchasing team as "bad motor."
I do not tell the buyer to increase the breaker. That is not a procurement shortcut. I ask the buyer to have the electrician record supply voltage, line current, protection device type, overload setting, cable run, connection method, and whether the motor is started across the line, through a soft starter, or through a VFD. Drive and motor documentation also keeps the responsibility tied to application data, technical requirements, and local safety rules.[С4][С5]
For importers, this proof protects both sides. If the site evidence is missing, the supplier may quote the correct motor and still lose the warranty argument later. If the supplier evidence is missing, the buyer may receive a motor that cannot match the protection and starting method.
✓
Site voltage, phase condition, cable path, breaker, overload relay, and starter information should be checked before treating a startup trip as a motor quality claim. True
The trip can come from the supply and protection boundary, not only from the electric motor.
×
If the motor trips on startup, the buyer should first ask for a larger breaker so production can continue. False
Changing protection without proving the failure model can create safety, warranty, and equipment risk.
How Does Starting Load Change the Motor Decision?
How Does Starting Load Change the Motor Decision?
The same 3 phase motor can behave very differently under no load and under a jammed or heavy starting load. I have seen buyers test a motor uncoupled, see it run, then reconnect the belt, pump, fan, or grinder and trip again. That does not prove the motor is good or bad by itself. It proves the RFQ is not complete.
For the supplier quotation, I want to know whether the machine starts empty or loaded, whether material can block the machine, whether the load has high inertia, and how often the motor starts per hour. Motor specification references include duty and operating conditions because heat, current, and starting stress depend on the real application.[С2][С3]
This is where a low price can become expensive. A supplier who quotes only a standard low voltage motor may be cheaper than a supplier who asks for load proof, but only one of those quotations is trying to control the actual startup risk.
✓
Starting-load proof belongs in the RFQ when a 3 phase motor trips during startup. True
The motor, starter, protection, and warranty boundary depend on whether the machine starts empty, loaded, jammed, or with high inertia.
×
If a 3 phase motor runs uncoupled, the supplier can ignore the driven machine when quoting. False
Running uncoupled does not prove the motor package will start the real load without tripping.
Should the Buyer Quote DOL, Soft Starter, or VFD?
Should the Buyer Quote DOL, Soft Starter, or VFD?
Many buyers jump from a startup trip to "quote me a VFD." Sometimes a VFD is the correct path. Sometimes the better answer is a correctly selected starter, corrected protection setting, better site wiring, a different acceleration plan, or a different motor specification.
The RFQ should not hide this choice. If the buyer wants direct-on-line starting, say so. If a soft starter is required, ask who selects the starter and protection. If a VFD motor package is required, ask for motor rated current, drive current rating, overload duty, acceleration requirement, cooling expectation, and cable/filter boundary. Drive selection documents focus on application, motor data, voltage, current, overload duty, and rating instead of price alone.[С4][С5]
I usually put the starting method in one line of the RFQ. It prevents one supplier from quoting a bare electric motor while another supplier quotes a complete VFD motor package. Those are not the same offer.
✓
DOL, soft starter, and VFD quotations should be separated in the RFQ because they assign different responsibility for current, acceleration, protection, and commissioning. True
The buyer cannot compare prices fairly if one quote includes the starting solution and another quote only includes the motor.
×
A VFD automatically solves every 3 phase motor startup trip. False
A VFD still needs correct motor data, drive sizing, settings, cooling, wiring, and application proof.
What Should the Supplier Prove Before Shipment?
What Should the Supplier Prove Before Shipment?
Before shipment, I want the proof trail to match the RFQ. The supplier should confirm the offered motor model, rated power, voltage, frequency, current, RPM, mounting, enclosure, duty, and connection method. If the order includes starter or VFD scope, the quotation should show where that responsibility starts and ends.
For a buyer who has already suffered a startup trip, I also like photos before shipment: motor nameplate, terminal box, packing, and any agreed test record. These do not replace site commissioning. They help prevent the simple disputes: wrong voltage, wrong connection, wrong model, unclear accessory scope, or a package that nobody owns after delivery.
RFQ Template for Suppliers
Please quote a 3 phase electric motor for the attached nameplate, site power, starter/protection, and driven-machine information. Confirm rated power, voltage, frequency, current, RPM/poles, duty, insulation class, enclosure, mounting, connection method, starting method, overload/protection assumption, load/start condition, production time after deposit, packing method, warranty terms, and photos of the nameplate and terminal box before shipment. If you recommend DOL, soft starter, or VFD operation, please state the selection basis and the boundary of supplier responsibility.
✓
The supplier should connect the quotation to the buyer's site and load proof before shipment, especially when startup trips are already part of the buying history. True
This creates one written record for motor identity, starting method, and responsibility boundary.
×
Pre-shipment photos are unnecessary because startup-trip problems can only be checked after installation. False
Site commissioning still matters, but shipment proof can catch wrong nameplate, connection, model, accessory, and packing issues before loading.
When Should Dongchun Motor Enter the Discussion?
When Should Dongchun Motor Enter the Discussion?
Dongchun Motor can enter the discussion after the buyer has the evidence package. We supply B2B wholesale electric motors, including single phase motor, 3 phase motor, brake motor, VFD motor, and fan motor, and the quotation conversation becomes much cleaner when the buyer sends real operating details first.[С6]
For a distributor or machine builder, I would ask for the same proof whether the buyer chooses Dongchun or another supplier: nameplate, voltage/frequency, duty, enclosure, mounting, driven load, starter or VFD method, and protection boundary. A serious supplier should not be offended by those questions.
My factory-side view is simple: price comparison is useful only after the motor identity and application boundary are visible. Before that, a low price may only be a low-information price.
✓
Dongchun Motor should be compared after the buyer has proven the motor identity, site power, starting method, load, and shipment-proof requirements. True
That lets the buyer compare supplier capability on the same technical and commercial basis.
×
A supplier can quote a reliable 3 phase motor package without knowing site power, starter method, or driven load. False
Without those details, the quotation hides the same assumptions that cause startup-trip disputes.
Заключение
A 3 phase motor startup trip is not only a maintenance problem. It is also a procurement problem when the buyer compares price before proving the failure boundary.
The safer path is proof first: nameplate, site voltage, protection, starter or VFD method, load condition, duty, supplier scope, and shipment evidence. After that, the buyer can compare electric motor suppliers with a clear record instead of asking each supplier to guess the missing part of the machine.
Сноски
[С1]Reddit search evidence for 3 phase motor startup-trip questions, https://www.reddit.com/search/?q=3%20phase%20motor%20trips%20breaker%20startup, accessed 2026-07-29. Used only as customer pain-point evidence.
[С2]Reddit search evidence for motor overload relay trip discussions, https://www.reddit.com/search/?q=motor%20overload%20relay%20trips%203%20phase%20motor, accessed 2026-07-29. Used only as customer pain-point evidence.
[С3]WEG, "Specification of Electric Motors", https://static.weg.net/medias/downloadcenter/h32/hc5/WEG-specification-of-electric-motors-50039409-brochure-english-web.pdf, accessed 2026-07-29.
[С4]ABB, "Low voltage motors - Motor guide", https://library.e.abb.com/public/d4bd7a2f8f8a4a32b1e4b5f5c0d67d4e/Motor%20guide.pdf, accessed 2026-07-29.
[С5]Schneider Electric, "Altivar Machine ATV320 Installation Manual", https://www.se.com/us/en/download/document/NVE41289/, and Rockwell Automation, "PowerFlex AC Drives Selection Guide", https://literature.rockwellautomation.com/idc/groups/literature/documents/sg/pflex-sg002_-en-p.pdf, accessed 2026-07-29.
[С6]Dongchun Motor brand profile,brand-profile.md, accessed 2026-07-29.
