MOTOR SPEED CONTROLS & MOTOR DRIVES

Harrel, the Hi-tech Extrusion Systems Company

MOTOR SPEED CONTROLS

Many people think that the only way to improve the speed control performance of an installation is to replace the existing "d-c drive" with a "servo drive" or an "a-c vector drive". Actually, however, none of these three descriptive names in any way defines the accuracy of the speed control.

Let's define the common types of drives:

"D-C DRIVE". Commonly refers to a motor where the current to the armature is transferred by brushes and a commutator.

"SERVO DRIVE" Technically speaking, a drive which controls something at a remote point. Traditionally, a type 0 servo controls position. A type 1 controls rate of change, or RPM. And a type 2 controls acceleration.
In practice a servo drive is normally a d-c drive or brushless drive with a longer ratio of length to diameter than normal. The smaller relative diameter reduces the inertia and allows faster response.
"BRUSHLESS D-C MOTOR" commonly refers to a systen using a motor with a permanent magnet rotor and no brushes.

"VECTOR DRIVE" commonly refers to a variable speed system using a motor with a squirrel cage rotor -- that is, a normal a-c motor construction -- in conjunction with electronic control of the current into the windings.

Note that none of these definitions says anything about the accuracy of the speed control. In each case, that accuracy is determined, not by the method that power is conducted to the rotor, but by a control system of some sort. And it is just as feasible to put a very accurate control system on a d-c drive as on an a-c vector drive or a brushless d-c motor!

RPM CONTROL

A d-c motor has an armature turning in a magnetic field, so it generates a back emf proportional to the speed. If high precision motor speed control is not required, this "back emf" can be used as a measure of the rotor speed in a system of so-called armature voltage control. The uncertainty in the voltage drop in the windings (IR drop) limits speed control accuracy to 3% - 5%.

Over the years separate tachometers were added -- a-c tachs measure to 2%, and d-c tachs to 0.5% to 1.0%. Then, with the advent of the digital revolution, the use of digital tachometers and piezoelectric crystal standards arrived. Harrel was one of the pioneers in adapting digital techniques to motor control.

Harrel offers two forms of digital control. The basic Harrel d-c drives use a digital tach and give 0.5% accuracy and regulation. For even closer control a 1/4 DIN control module is added which uses phase locked loop techniques to yield 0.001% accuracy and regulation.

This module has two applications. First, it can be used to upgrade Harrel drives, or those of any other manufacturer to 0.001% speed regulation. Second, it can be used to synchronize any number of motors to each other. This synchronization is exact -- 0.000% error in synchronization!

MC-101 DIGISYNCH ^® D-C DRIVE CONTROLLER

Used in Harrel d-c drive system to give 0.001% accuracy and regulation

May also be used to upgrade d-c drives of any manufacturer to 0.001%.

1/4 DIN plug-in mount -- for easy maintenance.
Large digital display may be calibrated in any units -- RPM, FPM, etc.

Computer compatible.

PRICE: $965.00

MC-101 SLAVE SPEED CONTROLLER

Slaves speed of auxiliary motor to MC-101 on primary motor.

May be used to synchronize any numer of motors.

Synchronization of all motor speeds is exact -- 0.000% steady state synchronization error!

Harrel dual zone temperature controllers

DIGITAL D-C DRIVES

Uses time-proven d-c motors.

Built-in digital DIGISENSE^®circuitry provides 0.5% accuracy and regulation.

When MC-101 DIGISYNCH controller is used, gives 0.001% accuracy and regulation.

Any number of motors may be synchronized in exact ratio -- 0.000% steady staate synchronization error!

Integral fusing, transient protection, and field loss protection included.

Current limiting, acceleration/deceleration limiting, max speed, min speed, and IR compensation included.

Control circuitry isolated from power line.

1 HP - 250 HP, 50/60 Hz, 115 - 550 volts

Controlled speed range: 20:1

115 VOLT, SINGLE PHASE
Max HP	Max Amps	Chassis	Price	Enclosed	Price
1	10	MD-101	$840	ED-101	$2,040
2	20	MD-102	$895	ED-102	$2,095
3	30	MD-103	$985	ED-103	$2,185

208-230 VOLT SINGLE PHASE

Max HP	Max Amps	Chassis	Price	Enclosed	Price
2	10	MD-202	$840	ED-202	$2,040
4	20	MD-204	$895	ED-204	$2,095
6	30	MD-206	$985	ED-206	$2,185

208-230 VOLT, 3 PHASE
Max HP	Max Amps	Chassis	Price	Enclosed	Price
5	17	MD-205	$3,650	ED-205	$5,110
7.5	25	MD-207	$3,650	ED-207	$5,110
10	34	MD-210	$3,650	ED-210	$5,110
15	51	MD-215	$3,850	ED-215	$5,410
20	68	MD-220	$3,850	ED-220	$5.410
25	85	MD-225	$3,850	ED-225	$5,410
30	102	MD-230	$5,950	ED-230	$7,750
40	136	MD-240	$5,950	ED-240	$7,950
50	169	MD-250	$5,950	ED-250	$7,950
60	203	MD-260	$5,950	ED-260	$7,950
75	254	MD-275	$5,950	ED-275	$7,950
100	339	MD-2100	$8,450	ED-2100	$16,750
125	425	MD-2125	$8,450	ED-2125	$16,750

480 Volt, 3 Phase
Max HP	Max Amps	Chassis	Price	Enclosed	Price
5	8.5	MD-405	$3,685	ED-405	$5,110
7.5	13	MD-407	$3,685	ED-407	$5,110
10	17	MD-410	$3,685	ED-410	$5,110
15	25	MD-415	$3,685	ED-415	$5,110
20	34	MD-420	$3,850	ED-420	$5,410
25	42	MD-425	$3,850	ED-425	$5,410
30	51	MD-430	$3,850	ED-430	$5410
40	68	MD-440	$3,850	ED-440	$5,410
50	85	MD-450	$3,850	ED-450	$5,410
60	102	MD-460	$5,950	ED-460	$7,950
75	127	MD-475	$5,950	ED-475	$7,950
100	170	MD-4100	$5,950	ED-4100	$7,950
125	212	MD-4125	$5,950	ED-4125	$7,950
150	255	MD-4150	$5,950	ED-4150	$7,950
200	340	MD-4200	$8,450	ED-4200	$16,750
250	425	MD-4250	$8,450	ED-4250	$16,750

Prices subject to change without notice

To order a Motor Drive or a Motor Speed Controller on line, fill in the form below and click on "submit". Harrel will enter your order and send you an acknowledgement giving engineering data, payment information, and delivery date. Terms are 1/3 with order, 1/3 immediately prior to shipment, and 1/3 net, 30 days. Alternatively, you may prefer to pay by credit card (Mastercaard or Visa -- number given by telephone when the order is entered.