Beckwith Electronics

Hamburg, Illinois 62045
(618) 232-1139

(618) 232-1172 fax

Contact Us

Hurst Manufacturing


Brushless DC Motors
Introduction
Selection Guide
BLDC
Introduction to Stepping Motors
Introduction to Controls
LSD & LSG PAS & PBS BAS
RAS & RBS SAS & SBS TS
YAS35 & YAS42 SCS
Synchronous Motors
A & AB BA PA & PB RA
SA & SB SC T & TA YA
Timing Motor and Timers
M Series
Cycle & Interval Timers
Reluctance Synchronous and
Induction Motors -
 KH & KN  KS
Brushed DC Motors
KD Series
Synchronous Motors, Hysteresis
AR-DA & PC-DA DA & DB
EA & EF MB HB CA GA
Permanent Magnet,
Linear Acuators
LA/LB & LAS/LBS
SSL, SLB, SLS, & SBLS

Hurst Motor Selection Guide
Variable
Speed
NT Dynamo Brushless DC Motor
Advantages
Dynamic Braking
High Efficiency
No Brush Wear
Reliable
Reduced EMI & RFI
Low Rotor Inertia
Disadvantages
Requires Controller
Complex Drive
Analog Control 50 oz-in DMA
External Control 50 oz-in DMB
Digital Control 50 oz-in DMC
PWM Control 50 oz-in DMD
Spur Gear 200 oz-in DM
Planetary Gear 149 in-lb MM
Other Gear   
Brushed DC Motor
Advantages
Dynamic Braking
High Efficiency
Disadvantages
Demag at low temperatures
Brush Wear
EMI
Direct Current 237 oz-in KD
Hybrid Stepper Introduction
1.8° Step Size 17 25 oz-in H17
Size 17 44 oz-in H17ET
NEMA 23 83 oz-in H23R
NEMA 23 187 oz-in H23S
Permanent Magnet DC Stepper
7.5° Step 35 MM 150 oz-in LS 35
42 MM 150 oz-in LS 42
Square 200 oz-in PAS
Compact 200 oz-in SAS
Compact 20.5 oz-in SCS
Heavy-Duty 250 oz-in TS
15° Step Square 200 oz-in PBS
Compact 200 oz-in SBS
 
Fixed
Speed
Permanent Magnet AC Synchronous
  35 MM 150 oz-in LY 35
42 MM 150 oz-in LY 42
  150 oz-in A/AB
Square 200 oz-in PA/PB
Compact 200 oz-in SA/SB
Compact 20.5 oz-in SC
Heavy-Duty 250 oz-in T
AC Induction
  High Slip 250 oz-in KH
Normal Slip 250 oz-in KN
Linear Actuator
  Linear 10 lbs LA/LB
Linear 15 lbs SL/SBL

Application Information...Applications for Hurst Motors and other information

Torque is the product of a force and the radius at which it is applied. The British unit of torque is pound-feet and in smaller motors this unit is reduced to ounce-inches. The metric unit of torque is Newton-meter.

Few motors produce a single value of torque over their entire speed range so that a torque vs. speed curve is often necessary for torque evaluation. Definitions of terms used to describe specific points on the curve are listed below along with definitions of some other commonly used terms for motor torque specification.

Pull-In Torque: the maximum torque at which a synchronous motor (stepping motor included) can accelerate its load to synchronous speed.

Pull-Out Torque: the maximum torque which a synchronous motor (stepping motor included) can develop and still maintain synchronous speed.

Full-Load Torque: the torque developed by a non-synchronous motor at its rated full-load speed.

Breakdown Torque: the maximum torque that the motor can develop; it occurs as a point on the speed-torque curve below synchronous or full-load speed.

Locked-Rotor Torque: the torque developed with the rotor at standstill (stalled).

Holding or Static Torque (Stepping Motor): the torque required to displace the rotor from its equilibrium position with one or more stator phases energized with the rotor at rest.

Detent or Residual Torque (Permanent Magnet Motor): the torque developed in an unenergized motor when the permanent magnet rotor is displaced from a position of minimum stator reluctance.

VARIABLE FREQUENCY OPERATION OF AC MOTORS

Sometimes a single motor is specified for both 50 and 60 Hz operation. Since inductive reactance and capacitive reactance vary dissimilarly with frequency, optimum performance must usually be compromised when a single winding/capacitor combination is operated at different frequencies. Some types of motors are more sensitive than others to frequency changes. As a general rule synchronous motors and especially permanent magnet motors are more sensitive than induction motors. The factory should be consulted before 50/60 Hz operation of a motor is planned.

Operation over a wider frequency range is extremely difficult to accomplish with capacitor phased motors and is not recommended. Reliable operation requires a two phase power supply with applied voltage a function of frequency.

If gear units had no losses, the torque at the output shaft of a gear motor would equal the motor torque multiplied by the reduction of the gear train. Since all gearing does have some internal losses, the actual output torque will be less than the calculated no-loss value by a factor known as gearing efficiency. The efficiency of a gear train will vary with the number of gears. For rough approximation a value of 7% to 10% loss per gear may be assumed. When precise calculation is necessary for a specific gear reduction, values should be obtained from the factory.

When high gear reductions are used, the torque at the output shaft may exceed the strength of the gearing. For this reason a maximum torque value, a gear torque rating, must be specified to prevent gearing damage. Gear torque ratings are based upon a uniform, steady torque load. Dynamic or shock loads impose stresses which can exceed gearing strength or cause early fatigue failure. To some extent this can be taken into consideration in a reduced gear torque rating. However, dynamic braking with inertial loads or locking of the output shaft can force the gearing to absorb destructive amounts of kinetic energy stored in the momentum of the load or the rotor with immediate or rapid failure. As an example, permanent magnet motors with gear trains should not be stalled since the inherent pulsating nature of the stall torque can cause gearing damage in a short period of time.



TEMPERATURE RISE AND INSULATION SYSTEMS

Temperature has an effect upon electrical resistance, magnetic characteristics, viscosity of lubricants, rate of volatilization of lubricants, dielectric strength of insulation and life of physical components in general. These effects must be taken into consideration in each motor application.

The temperature rise of a motor is the difference between the measured temperature of the motor winding and the ambient temperature. Electrical insulation systems are classified according to the maximum temperature that they can withstand. Hurst motors have either Class A or Class B insulation systems which are rated at 105oC and 130oC respectively for the hottest-spot temperature. A hot-spot allowance must be made for the difference between the measured temperature of the winding and the actual temperature of the hottest spot within the winding, usually 50 to 150oC depending upon the type of motor construction. The sum of the temperature rise, the hot-spot allowance, and the temperature of the ambient must not exceed the temperature rating of the insulation.

The temperature rise of a motor should also be specified at a particular operating point, e.g., no-load, full-load, or locked-rotor. Many of the Hurst motors are "impedance protected," that is, they are designed with enough impedance in the windings to limit the locked rotor currents to values that do not cause the motor to overheat beyond a safe temperature. Other motors are available with a thermal protector, a device installed adjacent to the stator winding which will disconnect the motor from the line should the winding temperature increase beyond a safe value.

The life of the electrical insulation and of the lubricants are adversely affected by high temperatures. A generally accepted "rule of thumb" is that for every 10oC increase in operating temperature, life is halved.


UL and CSA Certifications for our products
UNDERWRITERS' LABORATORIES RECOGNITION

MODEL QUALIFICATION UL CARD
A & AB 115V, 60 Hz
Standard Rotor
E37163, Component - Time-Indicating and Recording Appliances
 
AR-DA 115V, 60 Hz E53578(N), Componet - Impedance Protected Motors
 
CA 115V,60 Hz E37163, Componet - Time-Indicating and Recording Appliances
 
DA-DB 115V,60 Hz E37163, Componet - Time-Indicating and Recording Appliances
 
EA 115V,60 Hz E37163, Componet - Time-Indicating and Recording Appliances
 
GA 115V,60 Hz E37163, Componet - Time-Indicating and Recording Appliances
 
HB 115V,60 Hz
Class 105(A)
Insulation System
E52207, Componet - Systems, Electrical Insulation
 
KH, KN, KS 115V,60 Hz
Class 105(A)
Insulation System
E52207, Componet - Systems, Electrical Insulation
E53578(N), Componet - Impedance Protected Motors
 
LA & LB 115V,60 Hz
Standard Rotor
E53578(N), Componet - Impedance Protected Motors
 
MB 115V,60 Hz
Class 105(A)
Insulation System
E52207, Componet - Systems Electrical Insulation
E52177 Componet - Motors
 
PA & PB 115V,60 Hz,
Standard Rotor
E53578(N), Componet - Impedance Protected Motors
 
PC-DA 115V,60 Hz E53578(N), Componet - Impedance Protected Motors
 
RA 115V,60 Hz
Standard Rotor
E53578(N), Componet - Impedance Protected Motors
 
SA, SC 115V,60 Hz E53578(N), Componet - Impedance Motors
 
T, TA 115V
Standard Rotor
E53578(N), Componet - Impedance Protected Motors


CANADIAN STANDARDS ASSOCIATION CERTIFICATION:
CARD NO. 42576, MOTORS AND GENERATORS

MODEL QUALIFICATION
A 115V, 60 Hz, Standard Rotor, 3 watts max.
AB 115V, 60 Hz, 5 watts max.
AR-DA 115V, 60 Hz, 5 watts max.
CA 115V, 60 Hz, 5 watts max.
DA & DB 115V, 60 Hz, 5 watts max.
EA 115V, 60 Hz, 10 watts max.
GA 115V, 60 Hz, 10 watts max.
KN 115V, 60 Hz, 11/13 watts max.
MB 115V, 60 Hz, 1/100 hp, 30 watts max.
PA & PB 115V, 60 Hz, Standard Rotor, 7.5 watts max. PA, 10 watts max. PB
PC 115V, 60 Hz, 5 watts max.
RA 115V, 60 Hz, Standard Rotor, 11 watts max.
SC 115V, 60 Hz, 9 watts max.
T 115V, 60 Hz, Standard Rotor, 7 watts max.