Fully Utilizing the PKP High Torque Series

User avatar
om_tech_support_JT
Posts: 1058
Joined: Fri Mar 12, 2010 2:59 pm
Location: Torrance, CA
Contact:

Fully Utilizing the PKP High Torque Series

Postby om_tech_support_JT » Wed Jul 24, 2013 4:28 pm

Q: I'm considering switching my current PK series standard step motors to your new PKP series high torque series step motors. What are the differences that I should be aware of, and what else can I expect to gain besides being able to drive bigger loads and accelerate quicker?

A: Due to improvements in its design, our new PKP series stepper motors output higher torque than its predecessor, the PK series. There are many ways that the user can utilize the extra torque to maximize the performance of the motor. The obvious improvements would be bigger loads and quicker acceleration, but there are numerous other benefits which we will go over in this article.

First, I will focus on the one physical difference which is the added connector on the PKP series stepper motors compared to the traditional lead wires on the PK series stepper motors.

To best illustrate the differences, please see the side-by-side comparison below between a PK series model, PK264M-E2.0A, and its PKP series equivalent model, PKP264MD28AA-L.

PK vs PKP - PK264M-E2.0A vs PKP264MD28AA-L dimensions.jpg
PK vs PKP - PK264M-E2.0A vs PKP264MD28AA-L dimensions.jpg (124.84 KiB) Viewed 2238 times

PK vs PKP - same electrical specifications.jpg
PK vs PKP - same electrical specifications.jpg (66.78 KiB) Viewed 2238 times

SPECIFICATIONS AND DIMENSIONS
As you can see, besides higher torque output, there are only minor differences in the electrical winding specifications which will not affect its performance, and the only physical difference is the connector. As long as you have some space around the motor, you can incorporate the new PKP series motors easily. We also provide a free motor cable for all PKP series models.

The PKP series offers the same frame sizes available in the PK series (except for 85/90mm), 1.8 deg and 0.9 deg resolutions, encoder models, more bipolar windings options, and an improved SH spur type gearhead option for faster speeds with less backlash.

PK vs PKP - 0.9 degree resolution benefits.jpg
PK vs PKP - 0.9 degree resolution benefits.jpg (209.4 KiB) Viewed 2238 times

PK vs PKP - new PKP SH spur gearerd type offers faster speeds, lower backlash.jpg
PK vs PKP - new PKP SH spur gearerd type offers faster speeds, lower backlash.jpg (179.36 KiB) Viewed 2238 times

TORQUE COMPARISON
When comparing the new PKP series stepping motors to our older PK series stepping motors, the PKP series offers a torque increase of 1.2 to 1.7 times. This is due to improvements in the rotor/stator design, air gap thickness, winding density and magnet material.

PKP vs PK stepping motor torque comparison.jpg
PKP vs PK stepping motor torque comparison.jpg (113.47 KiB) Viewed 2238 times

BENEFITS OF HIGH TORQUE MOTORS:
Now let’s discuss how to maximize the performance of these high torque motors.

1. REDUCE CURRENT TO REDUCE POWER/ENERGY CONSUMPTION
We know that power in watts is volts x current, and we know that torque is proportional to current. Since the PKP series high torque stepping motors offers more available torque that may not be necessary, we can actually turn down the current setting to reduce the motor's torque which in turn will also reduce the motor's energy consumption.

2. REDUCE CURRENT, TORQUE TO REDUCE VIBRATION
Since too much excessive torque could turn into vibration, and current is proportional to torque, we can reduce the current for the PKP series high torque motor in order to reduce vibration.

PK vs PKP - reduce current, torque to reduce vibration.jpg
PK vs PKP - reduce current, torque to reduce vibration.jpg (174.22 KiB) Viewed 2238 times

3. REDUCE CURRENT TO REDUCE MOTOR OPERATING TEMPERATURE
Current is also proportional to a motor's operating temperature. Turning down the motor's current setting will also reduce the motor's operating temperature if temperature is an issue for your application.

PKP less power, energy consumption, and heat reduction.jpg
PKP less power, energy consumption, and heat reduction.jpg (126.61 KiB) Viewed 2238 times

4. REDUCE CURRENT, TEMPERATURE TO INCREASE MOTOR LIFE
It is known that around a 15 deg C reduction in bearing temperature approximately doubles the expected motor life. Since the bearing of a stepper motor is the only component that can fail, we base the life of a stepper motor on the bearing grease life. The grease life graph below shows this approximate increase in life.

PK vs PKP - bearing grease life curve.jpg
PK vs PKP - bearing grease life curve.jpg (85.81 KiB) Viewed 2238 times

To show the exact difference in life, I’ve shown the actual calculations below for 95 deg C and 80 deg C motor surface temperature.

Logt=6.12-1.4×(n/Nmax)-(0.018-0.006×(n/Nmax))×T

t = average grease life in hours
n = speed in RPM
Nmax = max bearing speed with grease lubrication in RPM
T = motor surface temperature in deg C
NOTE: 0.25 </= n/Nmax </= 1; when n/Nmax < 0.25, assume n/Nmax = 0.25

If T = 95℃ and n/Nmax = 0.25, we have 15,940 hours
If T = 80℃ and n/Nmax = 0.25, we have 28,184 hours
If T = 70℃ and n/Nmax = 0.25, we have 41,210 hours

5. ABILITY TO DOWNSIZE MOTOR
Since the PKP series stepping motors offer more available torque, downsizing of the motor size is possible in many cases. The image below compares a 56.4 mm frame size PKP series motor and a 42mm frame size standard PK series motor which have very similar performance characteristics.

PK vs PKP - ability to downsize motor size and keep performance.jpg
PK vs PKP - ability to downsize motor size and keep performance.jpg (168.37 KiB) Viewed 2238 times

And if these benefits do not appease you, we are offering a new lower price for all PKP series stepper motors to make them even more cost-effective than the PK series stepper motors.

For more information, specifications, or dimensional drawings of the PKP series stepping motors, please click the link below:
http://www.orientalmotor.com/products/p ... ochure.pdf

For assistance on selecting drivers, controllers, and/or accessories for your PKP series stepper motor, please visit our website (http://www.orientalmotor.com) or discuss your requirements with our technical support group (800-468-3982 or [email protected]).

Return to “Stepping Motors & Controls”

Who is online

Users browsing this forum: No registered users and 2 guests