Motor Test

Motor Testing Equipment FAQ

Below is a list of frequently asked questions regarding the operation of our motor test equipment. Should you need further assistance, contact Magtrol or your local sales agent.
Click on the question for the answer:

Q What is the difference between Hysteresis, Eddy-current and Powder Dynamometers?

The difference between Eddy-current, magnetic powder and hysteresis brakes is the design of the brake itself. All have a rotor and stator of which the design is adapted to its technology. A coil (in the stator) produces a magnetic field when supplied by an excitation current.

Powder brakes… use a metallic powder between the rotor and stator of the brake. When excitation current is applied, the powder sticks on the rotor (according to the magnetic field line) and brakes by friction. Powder brakes have a strong (nominal) braking torque at 0 rpm but are limited in speed (up to 1000 to 3000 rpm depending on the size of the dynamometer).

Eddy-current brakes… have a splined rotor. The splined part of the rotor in the magnetic field produces the braking effect. Eddy-current dynamometers apply braking power proportional to the speed (no braking power at 0 rpm) and are specially adapted for middle to very high speed applications (up to 50,000 rpm or even 100,000 rpm).

Hysteresis brakes… have a stator in 2 parts with a rotor in the form of a cup rotating in the magnetic field, between 2 stator parts. Hysteresis brakes provide braking power from 0 rpm to middle range speed (up 10,000 to 20,000 rpm, depending on size).

Both hysteresis and Eddy-current dynamometers can work in a vertical application, but this has to be mentioned early (at RFQ), since vertical versions are special designs. Powder brakes are not adapted to vertical use.

Choose the right technology depending on your application, determining which torque in which speed range you would like to test.

Q I am searching for information on one of my existing Magtrol units but I am not finding anything. Do you still sell this equipment?

Magtrol continuously develops new products in order to meet our customers' growing motor test requirements. The older model you are searching for was probably replaced with a newer model which offers more features and employs the latest technologies. If you need further information on older/obsolete equipment, search the archived product manuals or contact Magtrol's Motor Test Sales.

Q What is the highest torque rating a Magtrol dynamometer can supply?
A The highest torque rated Magtrol dynamometer is a special design composed of two 4PB15 powder dynamometers mounted in line (4PB15+K+4PB15). It has a rating of 2400 N·m (1770 lb·ft) with a maximum speed of 2000 rpm.

Q I would like to upgrade my Magtrol dynamometer. What do I need to do?

Contact Magtrol and provide us with the following information:
  • Dynamometer type, model number and serial number
  • Electronic equipment used in system configuration (TSC, DES, Controller)
Having the serial number of the dynamometer will enable Magtrol to determine what is required for the upgrade (electronic board, speed sensor, etc). We also recommend that you send the dynamometer back to Magtrol for calibration after performing any upgrades. Magtrol can also perform the upgrade for you.

Q How much water pressure can be used in the WB/PB dynamometer's water cooling system?

0.1 to 2 bars maximum.

Q What is the appropriate water temperature for the WB/PB dynamometer cooling system?
A Water input temperature should be between 10 °C and 20 °C. If the dynamometer has not been used for a while, blow air into the cooling system to remove any residual water.

Q I just received my Magtrol dynamometer back from service. But when I plug it in, I have a high torque effect. What do I do?

The first thing you need to do upon receiving a dynamometer that has been serviced by Magtrol is to REMOVE THE SHIPPING BOLT.

  • Newer models HD-100 through HD-500:   On dynamometers with a framed cabinet, the shipping bolt is accessible from the bottom of the base plate.
  • HD-700 series:   The shipping bolt is located in the front pillow block just under the shaft.
  • Older models HD-100 through HD-705:   Remove the top cover of the cabinet. Locate the gray colored damper cylinder near the front panel. There is a damper arm that runs between the damper cylinder and the brake assembly. The shipping bolt is the long slotted screw that extends through the damper arm and down into the base plate.
  • WB/PB 2.7 series:  The restraining pin may not be properly installed. Refer to the manual.
  • WB/PB 65 series and WB/PB 115 series:  There are two Hex Head screws for overload protection during shipment that must be adjusted. Refer to the manual.

Q I just received a new HD-700 series dynamometer and I have plugged it in. I can zero it but when I try to run it, I can hear it loading but the torque changes very little or not at all. What do I do?
A The first thing you need to do upon receiving a new Magtrol HD-700 series Dynamometer is to REMOVE THE SHIPPING BOLT. (See above.)

Q Can I replace the powder in my PB series dynamometer?
A No. The dynamometer must be returned to Magtrol to have the powder replaced. The dynamometer must be completely disassembled and cleaned when replacing the powder. It is possible to add a small amount of powder to the dynamometer on site. Be sure that the dynamometer is in rotation when adding the powder to allow the powder to be evenly distributed.

Q Can I replace the load cell in my dynamometer?
A Yes, however it is a complicated procedure. We recommend returning the dynamometer to Magtrol for service. When the load cell is replaced new calibration is required.

Q Are older model dynamometers compatible with new electronics?
A Yes, however some of the dynamometers may need modification. Usually the speed pickup and in some cases the TSC board will need to be modified. Contact your Magtrol sales office for further details.

Q Can I repair the load cell in my dynamometer?
A No, load cells are delicate devices that require a skilled technician for repair.

Q Is it normal for the damper oil to leak on the HD series dynamometers?
A No, however if the dynamometer is inverted or shipped improperly some oil can leak. Making the damper more leak resistant would negatively influence the accuracy causing less sensitivity and friction in the damper.

Q Is it possible to add a thermostat to my hysteresis brake to protect it from overheating?
A No. The rotor is the part that can overheat and an accurate temperature can only be measured with an infrared sensor.

Back to top
Magtrol SA (Suisse): +41 26 407 3000 • | Magtrol Sarl (France): +33 1 40 09 6161 •
Contact English French German Chinese India Russian Systemes de test moteurs Capteurs de couple Systemes de charge-force-poids Regulation de tension Mesure de deplacement Transmetteurs rotatifs