Every week, the same six questions land in our inbox. Some come from maintenance teams replacing a burned-out single-phase motor. Others come from engineers deciding between a permanent magnet DC motor and a servo. And more often than you'd think, they are bearing questions.
I'm the quality manager at a motor supply company that sells and services LEESON motors. I review roughly 300 units a year before they ship — nameplate checks, wiring diagrams, bearing condition, the works. These are the answers I keep giving.
- What makes a LEESON motor different?
- Where do I find the 230V LEESON single phase motor wiring diagram?
- Is a LEESON direct current permanent magnet motor still worth buying?
- When are DC servo motors worth the extra cost?
- What is a cross roller bearing?
- What's a ball bearing?
What makes a LEESON motor different?
Full disclosure: my job is checking motors against specifications. Voltage, frame, amp draw, enclosure, rotation — that's what I verify before a motor goes into stock or out to a customer. From that vantage point, the biggest difference with a LEESON motor is documentation.
LEESON, now part of Regal Rexnord, publishes the kind of technical information that lets you verify a motor before installation: NEMA frame dimensions, wiring diagrams, catalog PDFs with performance data, and cross-reference details. In our Q1 2024 quality audit of 40+ motors from stock, the LEESON units matched their catalog specs — voltage, speed, amp draw, frame — without missing pieces. That sounds boring until you're standing in front of a replacement motor at 11 PM with a deadline in the morning.
NEMA MG-1 is the standard that defines motor performance, testing, and nameplate data for general-purpose AC and DC motors in North America. It's the baseline we use for incoming verification.
The other thing I notice is product line breadth. AC induction motors, permanent magnet DC gearmotors, servo motors, and linear actuators all fall under the same documentation system. Fewer surprises when replacement time comes.
Where do I find the 230V LEESON single phase motor wiring diagram?
Start with the motor itself. LEESON prints the connection diagram on the nameplate or inside the conduit box on many single-phase models. If it's not there, the instruction sheet that ships with the motor will have it. When that's missing, look up the specific model on the LEESON catalog page — the PDF for that exact motor, not a generic diagram from a forum.
Here's the catch: on a dual-voltage 115/230V motor, the 230V connection is usually a series arrangement of the two main windings, while 115V uses a parallel arrangement. Do not assume the jumpers are already positioned for the supply you have. Check the diagram, then verify the line-to-line voltage at the disconnect. I can't tell you how many motors get returned as 'dead' that were simply connected for the wrong voltage.
NEC Article 430 is the starting point for conductor sizing and overload protection on fixed electric motor circuits. Local code amendments can change the details, so check what applies to your site.
One practical tip: take a photo of the old motor's wiring before you disconnect it. It takes ten seconds and saves a service call later. And if you're reversing rotation, swap the leads shown in the diagram — guessing which wires to switch usually ends badly. I don't have hard data on miswire rates, but based on the photos I review, my sense is that wrong-voltage connection causes a decent share of premature single-phase failures.
Is a LEESON direct current permanent magnet motor still worth buying?
Yes — a LEESON direct current permanent magnet motor is still worth buying if your application calls for adjustable speed with a simple DC drive. Permanent magnets on the stator mean no field winding and no field losses. Speed is roughly proportional to armature voltage, so you get a clean, predictable speed range from a relatively inexpensive SCR or PWM drive.
The torque story is good too. Armature current sets torque, and a PMDC motor delivers strong starting torque in a compact package. That makes these motors a common fit for conveyors, feeders, mixers, and similar equipment where the controller needs to be simple and reliable.
What you give up is maintenance. Brushes and a commutator wear, and that's just physics. When we inspect incoming PMDC motors, we check brush seating and commutator finish because a poor brush interface shows up as sparking and short motor life. Keep spare brushes on the shelf and respect the duty cycle, and these motors run a long time.
In other words: not every motion problem needs a brushless revolution. Sometimes the old tech is the right tech.
When are DC servo motors worth the extra cost?
A DC servo motor is really one part of a closed-loop system: the motor, a feedback device like an encoder or resolver, and a drive that continuously compares commanded position or speed against actual values and corrects in real time. That closed-loop correction is the whole point.
Ask three things before you spec one:
Position repeatability. A stepper can hold position, but it can lose steps under shock loads. A servo knows its actual position because of the feedback.
Speed and acceleration. If your cycle needs rapid moves or changing loads, a servo adjusts torque on the fly. A cheaper motor may stall or require oversizing to cover the worst case.
Variable load. When the load changes from one cycle to the next, closed-loop control keeps quality consistent.
Honestly, I've seen servo motors oversold. If the machine just needs constant speed with a stop at the end, a PMDC motor or an induction motor with a VFD is cheaper and more forgiving. Servo motors fix positioning problems, not design problems.
I still second-guess one upgrade we quoted for a customer who kept losing steps on an indexing line. The servo package cost noticeably more, and I wondered if we were pushing them into overkill. Their cycle time dropped enough that they retrofitted two more lines. That's what the spec said it would do — it just took me a while to trust it.
What is a cross roller bearing?
A cross roller bearing is a compact rolling-element bearing where cylindrical rollers sit in V-shaped raceways between the inner and outer rings. Each roller runs at a right angle to the one next to it, alternating direction around the ring. That crossing pattern is why it's called a cross roller bearing.
Why bother? Because one bearing can handle radial loads, axial loads, and tilting moment loads at the same time. In a standard ball bearing arrangement, you often need two bearings — or an angular-contact pair — to manage that combination. A cross roller bearing does it in a single, relatively slim package with high rigidity.
You see them in rotary indexing tables, robotic joints, and some linear actuator designs where the motor drives an output that has to support an overhung load. A motor might spin the input, but the cross roller bearing is what keeps the load from deflecting the output.
From a quality standpoint, mounting matters. The raceways are machined to tight tolerances, and the bearing will not forgive a sloppy mounting surface. If you're replacing one, record any part markings and note which side faces the load. And honestly, I'm not sure why these bearings are still treated as exotic outside of robotics. My best guess is that legacy designs were built around ball bearings, and nobody wanted to re-engineer the bracket. But for moment loads, cross roller bearings are hard to beat.
What's a ball bearing?
A ball bearing is the component that lets a shaft rotate with low friction: hardened steel balls sit between an inner race and an outer race, with a cage keeping the balls evenly spaced. The contact area between each ball and the race is small — technically an elliptical zone, but much smaller than the line contact in a roller bearing. Less contact means less friction, which makes ball bearings excellent at higher speeds.
Most general-purpose electric motors use deep-groove ball bearings. A deep-groove bearing handles radial loads plus moderate axial thrust and runs quietly. That is why it dominates fractional and integral horsepower AC motors.
The two things I check on a bearing spec:
Internal clearance. C3 means a slightly larger-than-normal clearance, and it's common in motors because the shaft and inner ring get hotter than the outer ring during operation. A C3 clearance lets the bearing expand without preloading itself to death. Clearance classes follow standards like ISO 5753; CN is the normal clearance used in cooler-running machines.
Seals and shields. A shielded bearing (ZZ) keeps out larger debris while letting grease move more freely. A sealed bearing (2RS) is fully closed and is typically lubricated for life. In a dusty or washdown plant, sealed is usually the safer call.
ABEC tolerance classes, defined under ABMA standards, describe dimensional accuracy. ABEC-1 or ABEC-3 is sufficient for most 1800 RPM NEMA motors. Higher classes like ABEC-7 matter more for high-speed spindles than for a general-purpose pump motor.
I changed our replacement bearing spec to sealed units for one customer in a dusty environment and immediately wondered if I'd cut the grease life too short. Then I looked at their maintenance history. They never greased the old fittings anyway. Sealed was the realistic choice, not the cautious one.
Bearings are small parts. They're also the most common reason a motor comes back under warranty. Spec them like they matter.
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