7548RLY: Up to 100 Ap Current Source

The 7548RLYwas created to meet the demanding requirements of the power utility industry. Capable of outputting up to 100 amperes peak current, the 7548RLY is powerful enough to put protection relays, fuses and other critical components through a full range of tests.

It is capable of a controlled-voltage bandwidth of DC - 100 kHz and a controlled-current bandwidth of DC - 10 kHz. The low noise floor, low distortion and minimal phase error of the 75486RLY make it the ideal amplifier for power grid modeling.


For Protection Relay Production Testing and Commissioning

  • High compliance voltage allows the 7548RLY to drive electromechanical relays directly
  • Maintains phase accuracy for any load from a dead short to 0.25 ohms
  • Front panel indicators for rapid assessment of amplifier status
  • Protection circuitry protects from input overloads, improper output connection (including shorted and improper loads), over-temperature, over-current, and supply voltages that are too high or low

Key Performance Capabilities:

  • Up to 100 Ap (70A RMS) output power at 0.5 ohms
  • Up to 195 Vp output voltage
  • Standard transconductance of 20 ±0.2% from short to 1-ohm load
  • Residual noise of less than 2.5 mA peak, from 40 Hz to 600 Hz


Pulse/Burst Specifications




0.5 ohms 20 seconds 60 Hz Sine 57A RMS / 80.6A peak
DC 25A peak
0.5 seconds 60 Hz Sine 66A RMS / 93A peak
DC 70A peak
0.2 seconds 60 Hz Sine 66A RMS / 93A peak
DC 70A peak




Amplitude vs. Frequency at 1V input, 20A output,
amplifier transconductance set to 20:

Load Input Signal Transconductance
1 kHz 100 Hz
2 ohms Sine 19.9 20
1 ohm Sine 20 20
0.5 ohm Sine 20 20
Short* Sine 20 20

*Unimpeded wire.

Front & Back

7548RLY Front Panel
7548RLY Bakc Panel



Controlled-Current Bandwidth (0.25-ohm load): DC to 10 kHz
Maximum Output Current (0.5-ohm load): 70A RMS (100 Ap)
Maximum Output Voltage: 195 Vp
Maximum Output Power:: Dependent on load and frequency
Load Constraint for Maximum Output: 0.5 ohms + 200 mH (Note: all loads from 8-ohm to short are stable with 2 mH in series)
Output Offset Current: Less than 10.0 mA DC peak
Standard Transconductance (from short to 1-ohm load): 20 ±0.2%
Unit-to-Unit Phase Error (60 Hz): ±0.1 degrees
Residual Noise (40 to 600 Hz): Less than 2.5 mA peak
Out Accuracy:: Less than ±1%

Input Characteristics

Balanced with ground: Three terminal barrier block connector, 20k ohm differential
Unbalanced: BNC connector, 10k ohm single ended.
Max Input Voltage: ±10V, balanced or unbalanced
Common Mode Rejection(40 to 600 Hz): -58 dB minimum

Communication Capabilities

Current Monitor: 20A/V ± 1%; 10A/V ± 1% (differential configuration)
Reporting: System Fault, Over Temp, Over Voltage, Over Load
Remote Control via Interlock Connector: Force to Standby, Reset after a fault

Status Display, Control, I/O

Front Panel LED Displays indicate: Ready, Standby, Stop, and Fault conditions in the output stage
LCD Display: User-configurable for up to four simultaneous displays reporting one, two, or all four of the following: Voltage Peak, Voltage RMS, Current Peak, and Current RMS. If an amplifier fault condition occurs, the front panel display lists the type of fault condition and gives suggested corrective action,
Soft Touch Switches for:
Run, Stop, Reset
Back Panel Power Connection:NEMA-style locking receptacle; matching AC connector also included
Signal Output: Four-position barrier block (OUTPUT/COMMON/SAMPLED COMMON/CHASSIS GROUND)
Signal Input: User Selectable BNC or Barrier Strip, Balanced or Unbalanced
Interlock Connector: 25-pin D-sub connector used for amplifier control and status applications; also used in multi-amplifier applications


Over/Under Voltage:
± 10% from specified supply voltage amplifier is forced to Standby
Over Current:
Breaker protection on both main power and low voltage supplies
Over Temperature:
Separate Output transistor, heat sink, and transformer temperature monitoring and protection

Physical Characteristics

Black powder-coat chassis with all aluminum construction; designed for stand-alone or rack-mounted operation. The amplifier occupies seven EIA 19-inch-wide rack units
Weight: 160 lbs (72.5 kg)
AC Power: Three-phase, 208 VAC ±10%, 47-60 Hz, 30A AC service (400 VAC ±10%, 15A version available). A toggle switch circuit breaker opens all legs of the AC mains on excess current demand.
Operating Temperature:
10°C to 50°C (50°F to 122°F), maximum output Power de-rated above 30°C (86°F).
Humidity: 70% or less, non-condensing
Cooling: Forced air-cooling from front to back through removable filters via four 100 ft3/min. fans. No space is required between rackmounted amplifiers. Air filters are removable from the rear via one fastener per side and may be eliminated if cabinet filtration is provided.
Dimensions (HxWxD): 12.25” x 19” x 22.8” (31.1 cm x 48.3 cm x 57.8 cm)


7548RLY Datasheet

7548RLY Datasheet

Complete technical specifications

7548RLY/7796RLY Operator's Manual Supplement

Operator's Manual Supplement

For 7548RLY and 7796RLY amplifiers

SIM Interlock Connector Pinouts and Functions

SIM Interlock Connector Pinouts and Functions

For 7200 series and 75/7700 series amplifiers

DXF model for chassis

DXF Model for Chassis

For 7548 and 7548RLY amplifiers

STEP file for chassis

Step File for Chassis

For 7548 and 7548RLY amplifiers

Recommended Accessories



Ground Current Limiter

Active protection with red LED indicator; resettable




Voltage & Current Monitor

Convenient, scaled monitoring of voltage and current

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