Hysteresis Dynamometers (HD Series)

Hysteresis Dynamometers

Product Description

Hysteresis Brake Dynamometers (HD Series) are versatile and ideal for testing in the low to medium power range (maximum 14 kW intermittent duty).  With a Hysteresis Braking system, the Dynamometers do not require speed to create torque, and therefore can provide a full motor ramp from free-run to locked rotor.  Brake cooling is provided by convection (no external source), by compressed air or by dedicated blower, depending on the model.  All Magtrol Hysteresis Dynamometers have accuracy ratings of ± 0.25% to ± 0.5% full scale — depending on size and system configuration.
To better integrate dynamometers into systems, Magtrol offers both long and short base plates.  The shorter base plate facilitates easier motor mounting when used with T-slot tables and Magtrol Adjustable Motor Fixtures, where as the long base plates are better suited for table top testing.


  • 16 Standard Models with Maximum Torque from 2.5 oz·in to 500 lb·in (18 mN·m to 56.5 N·m)
  • Hysteresis Braking System: Provides precise torque loading independent of shaft speed
  • Motor Testing from No Load to Locked Rotor
  • Accuracy: ±0.25% to ± 0.5% (Full Scale)
  • Air Flow Sensor: For protection against overheating and operator error
  • Standard Torque Units: English, Metric and SI
  • Base Plate: Available in long or short versions
  • Custom Dynamometers: for special torque and speed requirements
  • Easy Calibration

The Hysteresis Braking System

All Magtrol Hysteresis Dynamometers absorb power with a unique Hysteresis Braking System which provides frictionless torque loading independent of shaft speed. The Hysteresis Brake provides torque by the use of two basic components – a reticulated pole structure and a specialty steel rotor/shaft assembly – fitted together but not in physical contact. Until the pole structure is energized, the drag cup can spin freely on its shaft bearings. When a magnetizing force from the field coil is applied to the pole structure, the air gap becomes a flux field and the rotor is magnetically restrained, providing a braking action between the pole structure and rotor.






Specifications and Drawings

ModelMaximum Torque Range
Maximum Torque Range
Maximum Speed (rpm)Kinetic Power - 5 Minutes (W)Kinetic Power - Continuous (W)Short Base Plate Downloads
HD-106-5N0.018 N·m2.5 oz·in30,000357pdf | step
HD-100-5N0.08 N·m11 oz·in25,0007520pdf | step
HD-400-5N0.28 N·m40 oz·in25,00020055pdf | step
HD-500-5N0.85 N·m120 oz·in25,00040080pdf | step
HD-510-5N0.85 N·m120 oz·in25,000750375pdf | step
HD-505-5N1.7 N·m240 oz·in25,000800160pdf | step
HD-515-5N1.7 N·m240 oz·in25,0001,500900pdf | step
HD-700-5N3.10 N·m440 oz·in25,000700150pdf | step
HD-710-5N3.10 N·m440 oz·in25,0001,500935pdf | step
HD-705-5N6.20 N·m55 lb·in25,0001,400300pdf | step
HD-715-5N6.20 N·m55 lb·in25,0003,4003,000pdf | step
HD-800-5N14.00 N·m125 lb·in12,0002,8001,800 pdf | step | t-slot base
HD-810-5N14.00 N·m125 lb·in12,0003,5003,000pdf | step | t-slot base
HD-805-5N28.0 N·m250 lb·in12,0005,3003,000pdf | step | t-slot base
HD-815-5N28.0 N·m250 lb·in12,0007,0006,000pdf | step | t-slot base
HD-825-5N56.5 N·m500 lb·in8,00014,00012,000pdf

Note: Operating at the continuous power rating for periods of up to 4 hours is acceptable. However, operating for extended periods at high temperatures will result in premature component and bearing failure. Limiting the length of the cycle and the component temperatures will guard against premature failure. Where continuous duty is desired for longer time intervals, component temperatures should be maintained less than 100°C; monitoring the outside brake surface temperature is a sufficient reference.

  • Model HD-510, HD-515, HD-800 and HD-805 Dynamometers require air cooling provided by user. Regulator and filter package is provided as standard equipment on these units. See data sheet for pressure ratings.
  • Blower package is included as standard equipment with Model HD-710, HD-715, HD-810, HD-815 and HD-825 Dynamometers.
  • All -5N(A) dynamometers are 5 Volt Output

Contact Magtrol for 6N (English), 7N (Metric) and 8N (SI) Specifications

Blower Dimensions

Allow approximately 6 in to 8 in (152 mm to 203 mm) between rear
of dynamometer base plate and blower for connection hardware.
Required hardware is supplied with the dynamometer.

Weight8.5 lb3.9 kg18 lb8.1 kg

Blower Power and Fuses

  • Models HD-710, HD‑715, HD-810 and ED-715 include the BL‑001 blower.
  • Models HD‑815 and ED-815 include the BL‑002 blower.
  • Model HD‑825 uses two BL‑002 blowers for cooling its two brake sets.
BL-001120 V600UL/CSA6.30 A | 250 V | SB
BL-001A240 V500IEC3.15 A | 250 V | T
BL-002120 V1,000UL/CSA15.00 A | 250 V | SB
BL-002A240 V1,000IEC6.30 A | 250 V | T


  • Motors:
    • Combustion engine (automotive, motorcycle, chainsaw, etc.)
    • Hybrid
    • Electric
    • Hydraulic (Aerospace, machinery)
  • Pumps (hydraulic, oil)
  • Propeller (Aerospace, marine, helicopter)
  • Automobile industry, torque measurement on labor and/or production (Formula 1, screen wiper, electrical windows, starter, generator, brake)
  • Reduction gear, gearboxes
  • Clutch, overload clutch
  • Motorized valve drill, pneumatic tools
  • Other machine tools


System Options

To help you select the components for your motor testing system, this table shows which (currently available) electronics and software support Magtrol’s different types of dynamometers.

ModelDescriptionHysteresis Dynamometers (including ED Series)Eddy-current DynamometersPowder Brake DynamometersDial Weight Dynamometers
DSP7000High-Speed Programmable Dynamometer Controller
6200Dynamometer Controller/Readout
TSC 401Torque/Speed Conditioner
5500Dynamometer Switch Box
5501Dynamometer Switch Box
M-TEST 7Motor Testing Software
DES 410/411Power Supply
5241Power AmplifierRequired for HD-825 Only
5200Power Supply
5210Current-Regulated Power Supply
5250Current-Regulated Power Supply
TABDynamometer Tables
AMFAdjustable Motor Fixtures
FMFFixed Motor Fixtures
PTT-Slot Base Plate
FRSFree-Run Speed Sensor
SBB 14Signal Breakout Box

Special Designs

Low Speed TestingFor low speed motors, such as gear motors with maximum speeds of less than 200 rpm, Magtrol offers additional encoder options that allow for increased resolution of the speed signal. Please refer to the data sheet for ordering information.
High Speed TestingFor certain models, Magtrol can provide a dynamometer which can operate at higher than rated speeds.
Mechanical ModificationsMagtrol can provide customized base plates, riser blocks and shaft modifications.
Analog OutputMagtrol can provide a 0-5 VDC analog output for the torque signal and a TTL speed signal from the dynamometer.

HD Tandem Dynamometer

Magtrol offers Hysteresis Dynamometers mounted in tandem. In tandem, motors of different size can be tested simultaneously using only one bench. This system also allows different brake – torque transducer configurations according to motor size.

HB 715 + TM 307 mounted in tandem with HB 815 + TM 310


Dynamometer Selection

Magtrol Dynamometers cover a wide range of Torque, Speed and Mechanical Power ratings. To select the appropriate size Dynamometer for your motor testing needs, you will need to determine the Maximum Torque, Speed and Power applied to the Dynamometer:

Maximum Torque

It is important to consider all torque points that are to be tested, not only rated torque, but also Locked Rotor and Breakdown Torque. Dynamometer selection should initially be based on the maximum torque requirement, subject to determining the maximum power requirements.

Maximum Speed

This rating is to be considered independent of torque and power requirements, and is the maximum speed at which the Dynamometer can be safely run under free run or lightly loaded conditions. It is not to be considered as the maximum speed at which full braking torque can be applied.

Maximum Power Ratings

These ratings represent the maximum capability of the Dynamometer Braking System to absorb and dissipate heat generated when applying a braking load to the motor under test. The power absorbed and the heat generated by the Dynamometer is a function of the Torque (T) applied to the motor under test, and the resulting speed (n) of the motor. This is expressed in these power (P) formulas:

SI:P (watts)=T (N·m)xn (rpm)x(1.047 × 10-1)
English:P (watts)=T (lb·in)xn (rpm)x(1.183 × 10-2)
Metric:P (watts)=T (kg·cm)xn (rpm)x(1.027 × 10-2)
All of Magtrol's controllers, readouts and software calculate horsepower
as defined by 1 hp = 550 lb·ft / s. Using this definition:
hp=P (watts)/745.7
To calculate power, use Magtrol's online motor power calculator

The Dynamometer’s ability to dissipate heat is a function of how long a load will be applied. For this reason, the Maximum Power ratings given are based on continuous operation under load, as well as a maximum of 5 minutes under load.

To safely dissipate heat and avoid Dynamometer failure, the maximum power rating
is the most important consideration in selecting a Dynamometer.